non functional - Page 117

In what areas might the use of F# be more appropriate than C#?

- by Peter McGrattan

Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#. EDIT: Edited based on feedback from close votes with the intent of reducing perceived ambiguity.

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Java: volatile guarantees and out-of-order execution

- by WizardOfOdds

Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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how to effectively modify index

- by daedlus

Hej everyone, problem : I am looking for right way to convert an index from clustered to non-clustered Description : I have a table as below in sybase db: dbo.UserLog Id | UserId |time | .... This is hash partitioned using UserId. Currently it has 2 indexes UserId : non-clustered time: clustered This table has about 20 million records. I now want to make UserId as clustered index and time as non-clustered index. is it correct to user alter index to change from clustered to non-clustered or do i drop index and recreate. does the fact that userId is used in hash partitioning have any implications to this? To me alter seems way to go but I have not yet tried this.

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My linux server takes more than an hour to boot. Suggestions?

- by jamieb

I am building a CentOS 5.4 system that boots off a compact flash card using a card reader that emulates an IDE drive. It literally takes about an hour to boot. The ultra-slow part occurs when Grub is loading the kernel. Once that's done, the rest of the boot process only takes about a minute to get to a login prompt. Does anyone have any suggestions? I suspect that it may have to do with UDMA. Everything IDE-related in my BIOS seems to checkout. The read performance hdparm is telling me 1.77 MB/s. Ouch! (But even at that rate, it still shouldn't take an hour to decompress and load the kernel) [root@server ~]# hdparm -tT /dev/hdc /dev/hdc: Timing cached reads: 2444 MB in 2.00 seconds = 1222.04 MB/sec Timing buffered disk reads: 6 MB in 3.39 seconds = 1.77 MB/sec Trying to enable DMA is a no-go though: [root@server ~]# hdparm -d1 /dev/hdc /dev/hdc: setting using_dma to 1 (on) HDIO_SET_DMA failed: Operation not permitted using_dma = 0 (off) Here's some command outputs that might help: System [root@server ~]# uname -a Linux server.localdomain 2.6.18-164.el5xen #1 SMP Thu Sep 3 04:47:32 EDT 2009 i686 i686 i386 GNU/Linux PCI info: [root@server ~]# lspci -v 00:00.0 Host bridge: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (rev 02) Subsystem: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub Flags: bus master, fast devsel, latency 0 Capabilities: [e0] Vendor Specific Information 00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller]) Subsystem: Intel Corporation 82945G/GZ Integrated Graphics Controller Flags: bus master, fast devsel, latency 0, IRQ 10 Memory at fdf00000 (32-bit, non-prefetchable) [size=512K] I/O ports at ff00 [size=8] Memory at d0000000 (32-bit, prefetchable) [size=256M] Memory at fdf80000 (32-bit, non-prefetchable) [size=256K] Capabilities: [90] Message Signalled Interrupts: 64bit- Queue=0/0 Enable- Capabilities: [d0] Power Management version 2 00:1d.0 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 Flags: bus master, medium devsel, latency 0, IRQ 16 I/O ports at fe00 [size=32] 00:1d.1 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 Flags: bus master, medium devsel, latency 0, IRQ 17 I/O ports at fd00 [size=32] 00:1d.2 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 Flags: bus master, medium devsel, latency 0, IRQ 18 I/O ports at fc00 [size=32] 00:1d.3 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 Flags: bus master, medium devsel, latency 0, IRQ 19 I/O ports at fb00 [size=32] 00:1d.7 USB Controller: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller Flags: bus master, medium devsel, latency 0, IRQ 16 Memory at fdfff000 (32-bit, non-prefetchable) [size=1K] Capabilities: [50] Power Management version 2 Capabilities: [58] Debug port 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1) (prog-if 01 [Subtractive decode]) Flags: bus master, fast devsel, latency 0 Bus: primary=00, secondary=01, subordinate=01, sec-latency=32 I/O behind bridge: 0000d000-0000dfff Memory behind bridge: fde00000-fdefffff Prefetchable memory behind bridge: 00000000fdd00000-00000000fdd00000 Capabilities: [50] #0d [0000] 00:1f.0 ISA bridge: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01) Subsystem: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge Flags: bus master, medium devsel, latency 0 Capabilities: [e0] Vendor Specific Information 00:1f.2 IDE interface: Intel Corporation 82801GB/GR/GH (ICH7 Family) SATA IDE Controller (rev 01) (prog-if 80 [Master]) Subsystem: Intel Corporation 82801GB/GR/GH (ICH7 Family) SATA IDE Controller Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 17 I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at f800 [size=16] Capabilities: [70] Power Management version 2 00:1f.3 SMBus: Intel Corporation 82801G (ICH7 Family) SMBus Controller (rev 01) Subsystem: Intel Corporation 82801G (ICH7 Family) SMBus Controller Flags: medium devsel, IRQ 17 I/O ports at 0500 [size=32] 01:04.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 18 I/O ports at de00 [size=256] Memory at fdeff000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 01:06.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 17 I/O ports at dc00 [size=256] Memory at fdefe000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 01:07.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 19 I/O ports at da00 [size=256] Memory at fdefd000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 hdparm ouput: [root@server ~]# hdparm /dev/hdc /dev/hdc: multcount = 0 (off) IO_support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 0 (off) keepsettings = 0 (off) readonly = 0 (off) readahead = 256 (on) geometry = 8146/16/63, sectors = 8211168, start = 0 [root@server ~]# hdparm -I /dev/hdc /dev/hdc: ATA device, with non-removable media Model Number: InnoDisk Corp. - iCF4000 4GB Serial Number: 20091023AACA70000753 Firmware Revision: 081107 Standards: Supported: 5 Likely used: 6 Configuration: Logical max current cylinders 8146 8146 heads 16 16 sectors/track 63 63 -- CHS current addressable sectors: 8211168 LBA user addressable sectors: 8211168 device size with M = 1024*1024: 4009 MBytes device size with M = 1000*1000: 4204 MBytes (4 GB) Capabilities: LBA, IORDY(can be disabled) Standby timer values: spec'd by Vendor R/W multiple sector transfer: Max = 2 Current = 2 DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2 udma3 udma4 Cycle time: min=120ns recommended=120ns PIO: pio0 pio1 pio2 pio3 pio4 Cycle time: no flow control=120ns IORDY flow control=120ns Commands/features: Enabled Supported: * Power Management feature set * WRITE_BUFFER command * READ_BUFFER command * NOP cmd * CFA feature set * Mandatory FLUSH_CACHE HW reset results: CBLID- above Vih Device num = 0 CFA power mode 1: enabled and required by some commands Maximum current = 100ma Checksum: correct

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Divide a large amount of text on an arbitrary number of equal parts.

- by kalininew

I probably already fed up with their stupid questions, but I have one more question. I have a large piece of text Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos, qui ratione voluptatem sequi nesciunt, neque porro quisquam est, qui dolorem ipsum, quia dolor sit, amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt, ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit, qui in ea voluptate velit esse, quam nihil molestiae consequatur, vel illum, qui dolorem eum fugiat, quo voluptas nulla pariatur? At vero eos et accusamus et iusto odio dignissimos ducimus, qui blanditiis praesentium voluptatum deleniti atque corrupti, quos dolores et quas molestias excepturi sint, obcaecati cupiditate non provident, similique sunt in culpa, qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet, ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat. Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos, qui ratione voluptatem sequi nesciunt, neque porro quisquam est, qui dolorem ipsum, quia dolor sit, amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt, ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit, qui in ea voluptate velit esse, quam nihil molestiae consequatur, vel illum, qui dolorem eum fugiat, quo voluptas nulla pariatur? At vero eos et accusamus et iusto odio dignissimos ducimus, qui blanditiis praesentium voluptatum deleniti atque corrupti, quos dolores et quas molestias excepturi sint, obcaecati cupiditate non provident, similique sunt in culpa, qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet, ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat. Quis autem vel eum iure reprehenderit, qui in ea voluptate velit esse, quam nihil molestiae consequatur, vel illum, qui dolorem eum fugiat, quo voluptas nulla pariatur? At vero eos et accusamus et iusto odio dignissimos ducimus, qui blanditiis praesentium voluptatum deleniti atque corrupti, quos dolores et quas molestias excepturi sint, obcaecati cupiditate non provident, similique sunt in culpa, qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet, ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat. Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, At the exit I need to divide the text on the "n" equal parts, so that in these parts was about the same amount of text. Then I these part are arranged in columns and the need for these columns look about the same height. Another condition: Tags you can break (I mean that if the tag "p" contains a lot of text, it can be divided into two parts, to bring in another column). I think this is a monumental task, I shall be grateful for any help.

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How to minimize total cost of shortest path tree

- by Michael

I have a directed acyclic graph with positive edge-weights. It has a single source and a set of targets (vertices furthest from the source). I find the shortest paths from the source to each target. Some of these paths overlap. What I want is a shortest path tree which minimizes the total sum of weights over all edges. For example, consider two of the targets. Given all edge weights equal, if they share a single shortest path for most of their length, then that is preferable to two mostly non-overlapping shortest paths (fewer edges in the tree equals lower overall cost). Another example: two paths are non-overlapping for a small part of their length, with high cost for the non-overlapping paths, but low cost for the long shared path (low combined cost). On the other hand, two paths are non-overlapping for most of their length, with low costs for the non-overlapping paths, but high cost for the short shared path (also, low combined cost). There are many combinations. I want to find solutions with the lowest overall cost, given all the shortest paths from source to target. Does this ring any bells with anyone? Can anyone point me to relevant algorithms or analogous applications? Cheers!

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Overloading assignment operator in C++

- by jasonline

As I've understand, when overloading operator=, the return value should should be a non-const reference. A& A::operator=( const A& ) { // check for self-assignment, do assignment return *this; } It is non-const to allow non-const member functions to be called in cases like: ( a = b ).f(); But why should it return a reference? In what instance will it give a problem if the return value is not declared a reference, let's say return by value?

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How to skip to next iteration in jQuery.each() util?

- by Josh

I'm trying to iterate through an array of elements. jQuery's documentation says: jquery.Each() documentation Returning non-false is the same as a continue statement in a for loop, it will skip immediately to the next iteration. I've tried calling 'return non-false;' and 'non-false;' (sans return) neither of which skip to the next iteration. Instead, they break the loop. What am i missing?

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What production software have you written in F# in the past year or so that you would previously hav

- by Peter McGrattan

Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#.

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Data Access from single table in sql server 2005 is too slow

- by Muhammad Kashif Nadeem

Following is the script of table. Accessing data from this table is too slow. SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[Emails]( [id] [int] IDENTITY(1,1) NOT NULL, [datecreated] [datetime] NULL CONSTRAINT [DF_Emails_datecreated] DEFAULT (getdate()), [UID] [nvarchar](250) COLLATE Latin1_General_CI_AS NULL, [From] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [To] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [Subject] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [Body] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [HTML] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [AttachmentCount] [int] NULL, [Dated] [datetime] NULL ) ON [PRIMARY] Following query takes 50 seconds to fetch data. select id, datecreated, UID, [From], [To], Subject, AttachmentCount, Dated from emails If I include Body and Html in select then time is event worse. indexes are on: id unique clustered From Non unique non clustered To Non unique non clustered Tabls has currently 180000+ records. There might be 100,000 records each month so this will become more slow as time will pass. Does splitting data into two table will solve the problem? What other indexes should be there?

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What was the most interesting question you were asked on the interview?

- by VItaliy

It can be IT or non-IT related

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In what specific areas has F# proven more applicable than C#?

- by Peter McGrattan

Over the last few years F# has evolved into one of Microsoft's fully supported languages employing many ideas incubated in OCaml, ML and Haskell. Over the last several years C# has extended it's general purpose features by introducing more and more functional language features: LINQ (list comprehension), Lamdas, Closures, Anonymous Delegates and more... Given C#'s adoption of these functional features and F#'s taxonomy as an impure functional language (it allows YOU to access framework libraries or change shared state when a function is called if you want to) there is a strong similarity between the two languages although each has it's own polar opposite primary emphasis. I'm interested in any successful models employing these two languages in your production polyglot programs and also the areas within production software (web apps, client apps, server apps) you have written in F# in the past year or so that you would previously have written in C#. EDIT: Altered title with the intent of reducing perceived ambiguity.

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AVG isolated a virus now non on Vista startup I get BHO.DLL not found. how do I fix this error?

- by waterfallrain

Hello, I had to run AVG to clear a virus but now when I start my laptop it gives a message of This application has failed to start because of BHO.DLL was not found. Re-installing this application may fix this problem. How do I turn off this message? I am getting this everytime I start up the system.

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java-maven2: How to include the a jar as depedency in pom so that I will be able to access test clas

- by flavour-of-bru

Hi, I have a set of functional jars(more than 3) that tests my source code. These jars just contains test classes and assisting asserter classes. I am creating a new performance jar that would import all the functional tests from these jars so that all can be run simultaneously. But when I include them as test dependencies in pom of current jar, what all I get to see is the classes in src/main/java. How can I include these functional jars as dependent jars so that I can also reference classes in src/test/java. In other words, how do I reference the test classes in other jars. In what way should I include the dependency as. Thanks for your support.

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What SQL query should I perform to get the result set expected?

- by texai

What SQL query should I perform to get the result set expected, giving the first element of the chain (2) as input data, or any of them ? table name: changes +----+---------------+---------------+ | id | new_record_id | old_record_id | +----+---------------+---------------+ | 1| 4| 2| | -- non relevant data -- | | 6| 7| 4| | -- non relevant data -- | | 11| 13| 7| | 12| 14| 13| | -- non relevant data -- | | 31| 20| 14| +----+---------------+---------------+ Result set expected: +--+ | 2| | 4| | 7| |13| |14| |20| +--+ I know I should consider change my data model, but: What if I couldn't? Thank you in advance!

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sudo apt-get update problem

- by Jeon

I have a problem with sudo apt-get update that I can't seem to fix and It's causing problems with alot of installations I want to do. I run Ubuntu 12.04. Ign http://ftp.availo.se precise InRelease Ign http://ftp.availo.se precise-updates InRelease Ign http://ftp.availo.se precise-backports InRelease Ign http://ftp.availo.se precise-security InRelease Get:1 http://repository.spotify.com stable InRelease [2,979 B] Ign http://ppa.launchpad.net precise InRelease Ign http://extras.ubuntu.com precise InRelease Ign http://archive.canonical.com precise InRelease Ign http://ppa.launchpad.net precise InRelease Ign http://ppa.launchpad.net precise InRelease Ign http://repository.spotify.com stable InRelease Ign http://ftp.availo.se precise Release.gpg Ign http://ftp.availo.se precise-updates Release.gpg Ign http://ftp.availo.se precise-backports Release.gpg Ign http://repository.spotify.com stable/non-free amd64 Packages/DiffIndex Hit http://ppa.launchpad.net precise Release.gpg Hit http://ppa.launchpad.net precise Release.gpg Hit http://archive.canonical.com precise Release.gpg Hit http://extras.ubuntu.com precise Release.gpg Ign http://ftp.availo.se precise-security Release.gpg Ign http://repository.spotify.com stable/non-free i386 Packages/DiffIndex Ign http://repository.spotify.com stable/non-free TranslationIndex Hit http://ppa.launchpad.net precise Release.gpg Hit http://archive.canonical.com precise Release Hit http://extras.ubuntu.com precise Release Ign http://ftp.availo.se precise Release Ign http://ftp.availo.se precise-updates Release Hit http://ppa.launchpad.net precise Release Hit http://archive.canonical.com precise/partner amd64 Packages Hit http://extras.ubuntu.com precise/main Sources Ign http://ftp.availo.se precise-backports Release Ign http://ftp.availo.se precise-security Release Hit http://ppa.launchpad.net precise Release Hit http://archive.canonical.com precise/partner i386 Packages Ign http://archive.canonical.com precise/partner TranslationIndex Hit http://ppa.launchpad.net precise Release Hit http://extras.ubuntu.com precise/main amd64 Packages Hit http://extras.ubuntu.com precise/main i386 Packages Ign http://ftp.availo.se precise/main TranslationIndex Ign http://ftp.availo.se precise/multiverse TranslationIndex Ign http://ftp.availo.se precise/restricted TranslationIndex Hit http://ppa.launchpad.net precise/main Sources Hit http://ppa.launchpad.net precise/main amd64 Packages Hit http://ppa.launchpad.net precise/main i386 Packages Ign http://ppa.launchpad.net precise/main TranslationIndex Ign http://extras.ubuntu.com precise/main TranslationIndex Ign http://ftp.availo.se precise/universe TranslationIndex Hit http://ppa.launchpad.net precise/main Sources Hit http://ppa.launchpad.net precise/main amd64 Packages Hit http://ppa.launchpad.net precise/main i386 Packages Ign http://ppa.launchpad.net precise/main TranslationIndex Hit http://ppa.launchpad.net precise/main Sources Hit http://ppa.launchpad.net precise/main amd64 Packages Hit http://ppa.launchpad.net precise/main i386 Packages Ign http://ppa.launchpad.net precise/main TranslationIndex Ign http://ftp.availo.se precise-updates/main TranslationIndex Ign http://ftp.availo.se precise-updates/multiverse TranslationIndex Ign http://ftp.availo.se precise-updates/restricted TranslationIndex Ign http://ftp.availo.se precise-updates/universe TranslationIndex Hit http://repository.spotify.com stable/non-free amd64 Packages Ign http://ftp.availo.se precise-backports/main TranslationIndex Ign http://ftp.availo.se precise-backports/multiverse TranslationIndex Ign http://ftp.availo.se precise-backports/restricted TranslationIndex Ign http://ftp.availo.se precise-backports/universe TranslationIndex Hit http://repository.spotify.com stable/non-free i386 Packages Ign http://archive.canonical.com precise/partner Translation-en_US Ign http://ftp.availo.se precise-security/main TranslationIndex Ign http://ftp.availo.se precise-security/multiverse TranslationIndex Ign http://ftp.availo.se precise-security/restricted TranslationIndex Ign http://ftp.availo.se precise-security/universe TranslationIndex Ign http://repository.spotify.com stable/non-free Translation-en_US Ign http://archive.canonical.com precise/partner Translation-en Ign http://repository.spotify.com stable/non-free Translation-en Ign http://extras.ubuntu.com precise/main Translation-en_US Ign http://extras.ubuntu.com precise/main Translation-en Ign http://ppa.launchpad.net precise/main Translation-en_US Ign http://ppa.launchpad.net precise/main Translation-en Ign http://ppa.launchpad.net precise/main Translation-en_US Ign http://ppa.launchpad.net precise/main Translation-en Ign http://ppa.launchpad.net precise/main Translation-en_US Ign http://ppa.launchpad.net precise/main Translation-en Err http://ftp.availo.se precise/main Sources 404 Not Found Err http://ftp.availo.se precise/restricted Sources 404 Not Found Err http://ftp.availo.se precise/universe Sources 404 Not Found Err http://ftp.availo.se precise/multiverse Sources 404 Not Found Err http://ftp.availo.se precise/main amd64 Packages 404 Not Found Err http://ftp.availo.se precise/restricted amd64 Packages 404 Not Found Err http://ftp.availo.se precise/universe amd64 Packages 404 Not Found Err http://ftp.availo.se precise/multiverse amd64 Packages 404 Not Found Err http://ftp.availo.se precise/main i386 Packages 404 Not Found Err http://ftp.availo.se precise/restricted i386 Packages 404 Not Found Err http://ftp.availo.se precise/universe i386 Packages 404 Not Found Err http://ftp.availo.se precise/multiverse i386 Packages 404 Not Found Err http://ftp.availo.se precise-updates/main Sources 404 Not Found Err http://ftp.availo.se precise-updates/restricted Sources 404 Not Found Err http://ftp.availo.se precise-updates/universe Sources 404 Not Found Err http://ftp.availo.se precise-updates/multiverse Sources 404 Not Found Err http://ftp.availo.se precise-updates/main amd64 Packages 404 Not Found Err http://ftp.availo.se precise-updates/restricted amd64 Packages 404 Not Found Err http://ftp.availo.se precise-updates/universe amd64 Packages 404 Not Found Err http://ftp.availo.se precise-updates/multiverse amd64 Packages 404 Not Found Err http://ftp.availo.se precise-updates/main i386 Packages 404 Not Found Err http://ftp.availo.se precise-updates/restricted i386 Packages 404 Not Found Err http://ftp.availo.se precise-updates/universe i386 Packages 404 Not Found Err http://ftp.availo.se precise-updates/multiverse i386 Packages 404 Not Found Err http://ftp.availo.se precise-backports/main Sources 404 Not Found Err http://ftp.availo.se precise-backports/restricted Sources 404 Not Found Err http://ftp.availo.se precise-backports/universe Sources 404 Not Found Err http://ftp.availo.se precise-backports/multiverse Sources 404 Not Found Err http://ftp.availo.se precise-backports/main amd64 Packages 404 Not Found Err http://ftp.availo.se precise-backports/restricted amd64 Packages 404 Not Found Err http://ftp.availo.se precise-backports/universe amd64 Packages 404 Not Found Err http://ftp.availo.se precise-backports/multiverse amd64 Packages 404 Not Found Err http://ftp.availo.se precise-backports/main i386 Packages 404 Not Found Err http://ftp.availo.se precise-backports/restricted i386 Packages 404 Not Found Err http://ftp.availo.se precise-backports/universe i386 Packages 404 Not Found Err http://ftp.availo.se precise-backports/multiverse i386 Packages 404 Not Found Err http://ftp.availo.se precise-security/main Sources 404 Not Found Err http://ftp.availo.se precise-security/restricted Sources 404 Not Found Err http://ftp.availo.se precise-security/universe Sources 404 Not Found Err http://ftp.availo.se precise-security/multiverse Sources 404 Not Found Err http://ftp.availo.se precise-security/main amd64 Packages 404 Not Found Err http://ftp.availo.se precise-security/restricted amd64 Packages 404 Not Found Err http://ftp.availo.se precise-security/universe amd64 Packages 404 Not Found Err http://ftp.availo.se precise-security/multiverse amd64 Packages 404 Not Found Err http://ftp.availo.se precise-security/main i386 Packages 404 Not Found Err http://ftp.availo.se precise-security/restricted i386 Packages 404 Not Found Err http://ftp.availo.se precise-security/universe i386 Packages 404 Not Found Err http://ftp.availo.se precise-security/multiverse i386 Packages 404 Not Found Ign http://ftp.availo.se precise/main Translation-en_US Ign http://ftp.availo.se precise/main Translation-en Ign http://ftp.availo.se precise/multiverse Translation-en_US Ign http://ftp.availo.se precise/multiverse Translation-en Ign http://ftp.availo.se precise/restricted Translation-en_US Ign http://ftp.availo.se precise/restricted Translation-en Ign http://ftp.availo.se precise/universe Translation-en_US Ign http://ftp.availo.se precise/universe Translation-en Ign http://ftp.availo.se precise-updates/main Translation-en_US Ign http://ftp.availo.se precise-updates/main Translation-en Ign http://ftp.availo.se precise-updates/multiverse Translation-en_US Ign http://ftp.availo.se precise-updates/multiverse Translation-en Ign http://ftp.availo.se precise-updates/restricted Translation-en_US Ign http://ftp.availo.se precise-updates/restricted Translation-en Ign http://ftp.availo.se precise-updates/universe Translation-en_US Ign http://ftp.availo.se precise-updates/universe Translation-en Ign http://ftp.availo.se precise-backports/main Translation-en_US Ign http://ftp.availo.se precise-backports/main Translation-en Ign http://ftp.availo.se precise-backports/multiverse Translation-en_US Ign http://ftp.availo.se precise-backports/multiverse Translation-en Ign http://ftp.availo.se precise-backports/restricted Translation-en_US Ign http://ftp.availo.se precise-backports/restricted Translation-en Ign http://ftp.availo.se precise-backports/universe Translation-en_US Ign http://ftp.availo.se precise-backports/universe Translation-en Ign http://ftp.availo.se precise-security/main Translation-en_US Ign http://ftp.availo.se precise-security/main Translation-en Ign http://ftp.availo.se precise-security/multiverse Translation-en_US Ign http://ftp.availo.se precise-security/multiverse Translation-en Ign http://ftp.availo.se precise-security/restricted Translation-en_US Ign http://ftp.availo.se precise-security/restricted Translation-en Ign http://ftp.availo.se precise-security/universe Translation-en_US Ign http://ftp.availo.se precise-security/universe Translation-en Fetched 2,979 B in 9s (328 B/s) W: GPG error: http://repository.spotify.com stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 082CCEDF94558F59 W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise/main/source/Sources 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise/restricted/source/Sources 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise/universe/source/Sources 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise/multiverse/source/Sources 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Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/main/binary-amd64/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/restricted/binary-amd64/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/universe/binary-amd64/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/multiverse/binary-amd64/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/main/binary-i386/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/restricted/binary-i386/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/universe/binary-i386/Packages 404 Not Found W: Failed to fetch http://ftp.availo.se/ubuntu/dists/precise-security/multiverse/binary-i386/Packages 404 Not Found E: Some index files failed to download. They have been ignored, or old ones used instead. I would appreciate a fix to this. Thank you for the help.

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So…is it a Seek or a Scan?

- by Paul White

You’re probably most familiar with the terms ‘Seek’ and ‘Scan’ from the graphical plans produced by SQL Server Management Studio (SSMS). The image to the left shows the most common ones, with the three types of scan at the top, followed by four types of seek. You might look to the SSMS tool-tip descriptions to explain the differences between them: Not hugely helpful are they? Both mention scans and ranges (nothing about seeks) and the Index Seek description implies that it will not scan the index entirely (which isn’t necessarily true). Recall also yesterday’s post where we saw two Clustered Index Seek operations doing very different things. The first Seek performed 63 single-row seeking operations; and the second performed a ‘Range Scan’ (more on those later in this post). I hope you agree that those were two very different operations, and perhaps you are wondering why there aren’t different graphical plan icons for Range Scans and Seeks? I have often wondered about that, and the first person to mention it after yesterday’s post was Erin Stellato (twitter | blog): Before we go on to make sense of all this, let’s look at another example of how SQL Server confusingly mixes the terms ‘Scan’ and ‘Seek’ in different contexts. The diagram below shows a very simple heap table with two columns, one of which is the non-clustered Primary Key, and the other has a non-unique non-clustered index defined on it. The right hand side of the diagram shows a simple query, it’s associated query plan, and a couple of extracts from the SSMS tool-tip and Properties windows. Notice the ‘scan direction’ entry in the Properties window snippet. Is this a seek or a scan? The different references to Scans and Seeks are even more pronounced in the XML plan output that the graphical plan is based on. This fragment is what lies behind the single Index Seek icon shown above: You’ll find the same confusing references to Seeks and Scans throughout the product and its documentation. Making Sense of Seeks Let’s forget all about scans for a moment, and think purely about seeks. Loosely speaking, a seek is the process of navigating an index B-tree to find a particular index record, most often at the leaf level. A seek starts at the root and navigates down through the levels of the index to find the point of interest: Singleton Lookups The simplest sort of seek predicate performs this traversal to find (at most) a single record. This is the case when we search for a single value using a unique index and an equality predicate. It should be readily apparent that this type of search will either find one record, or none at all. This operation is known as a singleton lookup. Given the example table from before, the following query is an example of a singleton lookup seek: Sadly, there’s nothing in the graphical plan or XML output to show that this is a singleton lookup – you have to infer it from the fact that this is a single-value equality seek on a unique index. The other common examples of a singleton lookup are bookmark lookups – both the RID and Key Lookup forms are singleton lookups (an RID lookup finds a single record in a heap from the unique row locator, and a Key Lookup does much the same thing on a clustered table). If you happen to run your query with STATISTICS IO ON, you will notice that ‘Scan Count’ is always zero for a singleton lookup. Range Scans The other type of seek predicate is a ‘seek plus range scan’, which I will refer to simply as a range scan. The seek operation makes an initial descent into the index structure to find the first leaf row that qualifies, and then performs a range scan (either backwards or forwards in the index) until it reaches the end of the scan range. The ability of a range scan to proceed in either direction comes about because index pages at the same level are connected by a doubly-linked list – each page has a pointer to the previous page (in logical key order) as well as a pointer to the following page. The doubly-linked list is represented by the green and red dotted arrows in the index diagram presented earlier. One subtle (but important) point is that the notion of a ‘forward’ or ‘backward’ scan applies to the logical key order defined when the index was built. In the present case, the non-clustered primary key index was created as follows: CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col ASC) ) ; Notice that the primary key index specifies an ascending sort order for the single key column. This means that a forward scan of the index will retrieve keys in ascending order, while a backward scan would retrieve keys in descending key order. If the index had been created instead on key_col DESC, a forward scan would retrieve keys in descending order, and a backward scan would return keys in ascending order. A range scan seek predicate may have a Start condition, an End condition, or both. Where one is missing, the scan starts (or ends) at one extreme end of the index, depending on the scan direction. Some examples might help clarify that: the following diagram shows four queries, each of which performs a single seek against a column holding every integer from 1 to 100 inclusive. The results from each query are shown in the blue columns, and relevant attributes from the Properties window appear on the right: Query 1 specifies that all key_col values less than 5 should be returned in ascending order. The query plan achieves this by seeking to the start of the index leaf (there is no explicit starting value) and scanning forward until the End condition (key_col < 5) is no longer satisfied (SQL Server knows it can stop looking as soon as it finds a key_col value that isn’t less than 5 because all later index entries are guaranteed to sort higher). Query 2 asks for key_col values greater than 95, in descending order. SQL Server returns these results by seeking to the end of the index, and scanning backwards (in descending key order) until it comes across a row that isn’t greater than 95. Sharp-eyed readers may notice that the end-of-scan condition is shown as a Start range value. This is a bug in the XML show plan which bubbles up to the Properties window – when a backward scan is performed, the roles of the Start and End values are reversed, but the plan does not reflect that. Oh well. Query 3 looks for key_col values that are greater than or equal to 10, and less than 15, in ascending order. This time, SQL Server seeks to the first index record that matches the Start condition (key_col >= 10) and then scans forward through the leaf pages until the End condition (key_col < 15) is no longer met. Query 4 performs much the same sort of operation as Query 3, but requests the output in descending order. Again, we have to mentally reverse the Start and End conditions because of the bug, but otherwise the process is the same as always: SQL Server finds the highest-sorting record that meets the condition ‘key_col < 25’ and scans backward until ‘key_col >= 20’ is no longer true. One final point to note: seek operations always have the Ordered: True attribute. This means that the operator always produces rows in a sorted order, either ascending or descending depending on how the index was defined, and whether the scan part of the operation is forward or backward. You cannot rely on this sort order in your queries of course (you must always specify an ORDER BY clause if order is important) but SQL Server can make use of the sort order internally. In the four queries above, the query optimizer was able to avoid an explicit Sort operator to honour the ORDER BY clause, for example. Multiple Seek Predicates As we saw yesterday, a single index seek plan operator can contain one or more seek predicates. These seek predicates can either be all singleton seeks or all range scans – SQL Server does not mix them. For example, you might expect the following query to contain two seek predicates, a singleton seek to find the single record in the unique index where key_col = 10, and a range scan to find the key_col values between 15 and 20: SELECT key_col FROM dbo.Example WHERE key_col = 10 OR key_col BETWEEN 15 AND 20 ORDER BY key_col ASC ; In fact, SQL Server transforms the singleton seek (key_col = 10) to the equivalent range scan, Start:[key_col >= 10], End:[key_col <= 10]. This allows both range scans to be evaluated by a single seek operator. To be clear, this query results in two range scans: one from 10 to 10, and one from 15 to 20. Final Thoughts That’s it for today – tomorrow we’ll look at monitoring singleton lookups and range scans, and I’ll show you a seek on a heap table. Yes, a seek. On a heap. Not an index! If you would like to run the queries in this post for yourself, there’s a script below. Thanks for reading! IF OBJECT_ID(N'dbo.Example', N'U') IS NOT NULL BEGIN DROP TABLE dbo.Example; END ; -- Test table is a heap -- Non-clustered primary key on 'key_col' CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ; -- Non-unique non-clustered index on the 'data' column CREATE NONCLUSTERED INDEX [IX dbo.Example data] ON dbo.Example (data) ; -- Add 100 rows INSERT dbo.Example WITH (TABLOCKX) ( key_col, data ) SELECT key_col = V.number, data = V.number FROM master.dbo.spt_values AS V WHERE V.[type] = N'P' AND V.number BETWEEN 1 AND 100 ; -- ================ -- Singleton lookup -- ================ ; -- Single value equality seek in a unique index -- Scan count = 0 when STATISTIS IO is ON -- Check the XML SHOWPLAN SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 32 ; -- =========== -- Range Scans -- =========== ; -- Query 1 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col <= 5 ORDER BY E.key_col ASC ; -- Query 2 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col > 95 ORDER BY E.key_col DESC ; -- Query 3 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 10 AND E.key_col < 15 ORDER BY E.key_col ASC ; -- Query 4 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 20 AND E.key_col < 25 ORDER BY E.key_col DESC ; -- Final query (singleton + range = 2 range scans) SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 10 OR E.key_col BETWEEN 15 AND 20 ORDER BY E.key_col ASC ; -- === TIDY UP === DROP TABLE dbo.Example; © 2011 Paul White email: [email protected] twitter: @SQL_Kiwi

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A Taxonomy of Numerical Methods v1

- by JoshReuben

Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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Data Masking Pack 12.1.0.3 Certified with E-Business Suite 12.1.3

- by Elke Phelps (Oracle Development)

I'm pleased to announce the certification of the E-Business Suite 12.1.3 Data Masking Template for the Data Masking Pack with Enterprise Manager Cloud Control 12.1.0.3. You can use the Oracle Data Masking Pack with Oracle Enterprise Manager Grid Control 12c to scramble sensitive data in cloned E-Business Suite environments. You may scramble data in E-Business Suite cloned environments with EM12.1.0.3 using the following template: E-Business Suite 12.1.3 Data Masking Template for Data Masking Pack with EM12c (Patch 18462641) What does data masking do in E-Business Suite environments? Application data masking does the following: De-identify the data: Scramble identifiers of individuals, also known as personally identifiable information or PII. Examples include information such as name, account, address, location, and driver's license number. Mask sensitive data: Mask data that, if associated with personally identifiable information (PII), would cause privacy concerns. Examples include compensation, health and employment information. Maintain data validity: Provide a fully functional application. How can EBS customers use data masking? The Oracle E-Business Suite Template for Data Masking Pack can be used in situations where confidential or regulated data needs to be shared with other non-production users who need access to some of the original data, but not necessarily every table. Examples of non-production users include internal application developers or external business partners such as offshore testing companies, suppliers or customers. Due to data dependencies, scrambling E-Business Suite data is not a trivial task. The data needs to be scrubbed in such a way that allows the application to continue to function. The template works with the Oracle Data Masking Pack and Oracle Enterprise Manager to obscure sensitive E-Business Suite information that is copied from production to non-production environments. The Oracle E-Business Suite Template for Data Masking Pack is applied to a non-production environment with the Enterprise Manager Grid Control Data Masking Pack. When applied, the Oracle E-Business Suite Template for Data Masking Pack will create an irreversibly scrambled version of your production database for development and testing. Is there a charge for this? Yes. You must purchase licenses for the Oracle Data Masking Pack to use the Oracle E-Business Suite 12.1.3 template. The Oracle E-Business Suite 12.1.3 Template for the Data Masking Pack is included with the Oracle Data Masking Pack license. You can contact your Oracle account manager for more details about licensing. References Additional details and requirements are provided in the following My Oracle Support Note: Using Oracle E-Business Suite Release 12.1.3 Template for the Data Masking Pack with Oracle Enterprise Manager 12.1 Data Masking Tool (Note 1481916.1) Masking Sensitive Data in the Oracle Database Real Application Testing User's Guide 11g Release 2 (11.2) Related Articles Scrambling Sensitive Data in E-Business Suite E-Business Suite 12.1.3 Data Masking Certified with Enterprise Manager 12c

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Useful PHP Extensions

An article about some useful PHP 5 extensions with a fully functional demo and all required files

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help with fixing fwts errors log

- by jasmines

Here is an extract of results.log: MTRR validation. Test 1 of 3: Validate the kernel MTRR IOMEM setup. FAILED [MEDIUM] MTRRIncorrectAttr: Test 1, Memory range 0xc0000000 to 0xdfffffff (PCI Bus 0000:00) has incorrect attribute Write-Combining. FAILED [MEDIUM] MTRRIncorrectAttr: Test 1, Memory range 0xfee01000 to 0xffffffff (PCI Bus 0000:00) has incorrect attribute Write-Protect. ==================================================================================================== Test 1 of 1: Kernel log error check. Kernel message: [ 0.208079] [Firmware Bug]: ACPI: BIOS _OSI(Linux) query ignored ADVICE: This is not exactly a failure mode but a warning from the kernel. The _OSI() method has implemented a match to the 'Linux' query in the DSDT and this is redundant because the ACPI driver matches onto the Windows _OSI strings by default. FAILED [HIGH] KlogACPIErrorMethodExecutionParse: Test 1, HIGH Kernel message: [ 3.512783] ACPI Error : Method parse/execution failed [\_SB_.PCI0.GFX0._DOD] (Node f7425858), AE_AML_PACKAGE_LIMIT (20110623/psparse-536) ADVICE: This is a bug picked up by the kernel, but as yet, the firmware test suite has no diagnostic advice for this particular problem. Found 1 unique errors in kernel log. ==================================================================================================== Check if system is using latest microcode. ---------------------------------------------------------------------------------------------------- Cannot read microcode file /usr/share/misc/intel-microcode.dat. Aborted test, initialisation failed. ==================================================================================================== MSR register tests. FAILED [MEDIUM] MSRCPUsInconsistent: Test 1, MSR SYSENTER_ESP (0x175) has 1 inconsistent values across 2 CPUs for (shift: 0 mask: 0xffffffffffffffff). MSR CPU 0 -> 0xf7bb9c40 vs CPU 1 -> 0xf7bc7c40 FAILED [MEDIUM] MSRCPUsInconsistent: Test 1, MSR MISC_ENABLE (0x1a0) has 1 inconsistent values across 2 CPUs for (shift: 0 mask: 0x400c51889). MSR CPU 0 -> 0x850088 vs CPU 1 -> 0x850089 ==================================================================================================== Checks firmware has set PCI Express MaxReadReq to a higher value on non-motherboard devices. ---------------------------------------------------------------------------------------------------- Test 1 of 1: Check firmware settings MaxReadReq for PCI Express devices. MaxReadReq for pci://00:00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) is low (128) [Audio device]. MaxReadReq for pci://00:02:00.0 Network controller: Intel Corporation PRO/Wireless 5100 AGN [Shiloh] Network Connection is low (128) [Network controller]. FAILED [LOW] LowMaxReadReq: Test 1, 2 devices have low MaxReadReq settings. Firmware may have configured these too low. ADVICE: The MaxReadRequest size is set too low and will affect performance. It will provide excellent bus sharing at the cost of bus data transfer rates. Although not a critical issue, it may be worth considering setting the MaxReadRequest size to 256 or 512 to increase throughput on the PCI Express bus. Some drivers (for example the Brocade Fibre Channel driver) allow one to override the firmware settings. Where possible, this BIOS configuration setting is worth increasing it a little more for better performance at a small reduction of bus sharing. ==================================================================================================== PCIe ASPM check. ---------------------------------------------------------------------------------------------------- Test 1 of 2: PCIe ASPM ACPI test. PCIE ASPM is not controlled by Linux kernel. ADVICE: BIOS reports that Linux kernel should not modify ASPM settings that BIOS configured. It can be intentional because hardware vendors identified some capability bugs between the motherboard and the add-on cards. Test 2 of 2: PCIe ASPM registers test. WARNING: Test 2, RP 00h:1Ch.01h L0s not enabled. WARNING: Test 2, RP 00h:1Ch.01h L1 not enabled. WARNING: Test 2, Device 02h:00h.00h L0s not enabled. WARNING: Test 2, Device 02h:00h.00h L1 not enabled. PASSED: Test 2, PCIE aspm setting matched was matched. WARNING: Test 2, RP 00h:1Ch.05h L0s not enabled. WARNING: Test 2, RP 00h:1Ch.05h L1 not enabled. WARNING: Test 2, Device 85h:00h.00h L0s not enabled. WARNING: Test 2, Device 85h:00h.00h L1 not enabled. PASSED: Test 2, PCIE aspm setting matched was matched. ==================================================================================================== Extract and analyse Windows Management Instrumentation (WMI). Test 1 of 2: Check Windows Management Instrumentation in DSDT Found WMI Method WMAA with GUID: 5FB7F034-2C63-45E9-BE91-3D44E2C707E4, Instance 0x01 Found WMI Event, Notifier ID: 0x80, GUID: 95F24279-4D7B-4334-9387-ACCDC67EF61C, Instance 0x01 PASSED: Test 1, GUID 95F24279-4D7B-4334-9387-ACCDC67EF61C is handled by driver hp-wmi (Vendor: HP). Found WMI Event, Notifier ID: 0xa0, GUID: 2B814318-4BE8-4707-9D84-A190A859B5D0, Instance 0x01 FAILED [MEDIUM] WMIUnknownGUID: Test 1, GUID 2B814318-4BE8-4707-9D84-A190A859B5D0 is unknown to the kernel, a driver may need to be implemented for this GUID. ADVICE: A WMI driver probably needs to be written for this event. It can checked for using: wmi_has_guid("2B814318-4BE8-4707-9D84-A190A859B5D0"). One can install a notify handler using wmi_install_notify_handler("2B814318-4BE8-4707-9D84-A190A859B5D0", handler, NULL). http://lwn.net/Articles/391230 describes how to write an appropriate driver. Found WMI Object, Object ID AB, GUID: 05901221-D566-11D1-B2F0-00A0C9062910, Instance 0x01, Flags: 00 Found WMI Method WMBA with GUID: 1F4C91EB-DC5C-460B-951D-C7CB9B4B8D5E, Instance 0x01 Found WMI Object, Object ID BC, GUID: 2D114B49-2DFB-4130-B8FE-4A3C09E75133, Instance 0x7f, Flags: 00 Found WMI Object, Object ID BD, GUID: 988D08E3-68F4-4C35-AF3E-6A1B8106F83C, Instance 0x19, Flags: 00 Found WMI Object, Object ID BE, GUID: 14EA9746-CE1F-4098-A0E0-7045CB4DA745, Instance 0x01, Flags: 00 Found WMI Object, Object ID BF, GUID: 322F2028-0F84-4901-988E-015176049E2D, Instance 0x01, Flags: 00 Found WMI Object, Object ID BG, GUID: 8232DE3D-663D-4327-A8F4-E293ADB9BF05, Instance 0x01, Flags: 00 Found WMI Object, Object ID BH, GUID: 8F1F6436-9F42-42C8-BADC-0E9424F20C9A, Instance 0x00, Flags: 00 Found WMI Object, Object ID BI, GUID: 8F1F6435-9F42-42C8-BADC-0E9424F20C9A, Instance 0x00, Flags: 00 Found WMI Method WMAC with GUID: 7391A661-223A-47DB-A77A-7BE84C60822D, Instance 0x01 Found WMI Object, Object ID BJ, GUID: DF4E63B6-3BBC-4858-9737-C74F82F821F3, Instance 0x05, Flags: 00 ==================================================================================================== Disassemble DSDT to check for _OSI("Linux"). ---------------------------------------------------------------------------------------------------- Test 1 of 1: Disassemble DSDT to check for _OSI("Linux"). This is not strictly a failure mode, it just alerts one that this has been defined in the DSDT and probably should be avoided since the Linux ACPI driver matches onto the Windows _OSI strings { If (_OSI ("Linux")) { Store (0x03E8, OSYS) } If (_OSI ("Windows 2001")) { Store (0x07D1, OSYS) } If (_OSI ("Windows 2001 SP1")) { Store (0x07D1, OSYS) } If (_OSI ("Windows 2001 SP2")) { Store (0x07D2, OSYS) } If (_OSI ("Windows 2006")) { Store (0x07D6, OSYS) } If (LAnd (MPEN, LEqual (OSYS, 0x07D1))) { TRAP (0x01, 0x48) } TRAP (0x03, 0x35) } WARNING: Test 1, DSDT implements a deprecated _OSI("Linux") test. ==================================================================================================== 0 passed, 0 failed, 1 warnings, 0 aborted, 0 skipped, 0 info only. ==================================================================================================== ACPI DSDT Method Semantic Tests. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP Failed to install global event handler. Test 22 of 93: Check _PSR (Power Source). ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 22, Detected an infinite loop when evaluating method '\_SB_.AC__._PSR'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. PASSED: Test 22, \_SB_.AC__._PSR correctly acquired and released locks 16 times. Test 35 of 93: Check _TMP (Thermal Zone Current Temp). ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 35, Detected an infinite loop when evaluating method '\_TZ_.DTSZ._TMP'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. PASSED: Test 35, \_TZ_.DTSZ._TMP correctly acquired and released locks 14 times. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 35, Detected an infinite loop when evaluating method '\_TZ_.CPUZ._TMP'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. PASSED: Test 35, \_TZ_.CPUZ._TMP correctly acquired and released locks 10 times. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 35, Detected an infinite loop when evaluating method '\_TZ_.SKNZ._TMP'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. PASSED: Test 35, \_TZ_.SKNZ._TMP correctly acquired and released locks 10 times. PASSED: Test 35, _TMP correctly returned sane looking value 0x00000b4c (289.2 degrees K) PASSED: Test 35, \_TZ_.BATZ._TMP correctly acquired and released locks 9 times. PASSED: Test 35, _TMP correctly returned sane looking value 0x00000aac (273.2 degrees K) PASSED: Test 35, \_TZ_.FDTZ._TMP correctly acquired and released locks 7 times. Test 46 of 93: Check _DIS (Disable). FAILED [MEDIUM] MethodShouldReturnNothing: Test 46, \_SB_.PCI0.LPCB.SIO_.COM1._DIS returned values, but was expected to return nothing. Object returned: INTEGER: 0x00000000 ADVICE: This probably won't cause any errors, but it should be fixed as the AML code is not conforming to the expected behaviour as described in the ACPI specification. FAILED [MEDIUM] MethodShouldReturnNothing: Test 46, \_SB_.PCI0.LPCB.SIO_.LPT0._DIS returned values, but was expected to return nothing. Object returned: INTEGER: 0x00000000 ADVICE: This probably won't cause any errors, but it should be fixed as the AML code is not conforming to the expected behaviour as described in the ACPI specification. Test 61 of 93: Check _WAK (System Wake). Test _WAK(1) System Wake, State S1. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 61, Detected an infinite loop when evaluating method '\_WAK'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. Test _WAK(2) System Wake, State S2. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 61, Detected an infinite loop when evaluating method '\_WAK'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. Test _WAK(3) System Wake, State S3. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 61, Detected an infinite loop when evaluating method '\_WAK'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. Test _WAK(4) System Wake, State S4. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 61, Detected an infinite loop when evaluating method '\_WAK'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. Test _WAK(5) System Wake, State S5. ACPICA Exception AE_AML_INFINITE_LOOP during execution of method COMP WARNING: Test 61, Detected an infinite loop when evaluating method '\_WAK'. ADVICE: This may occur because we are emulating the execution in this test environment and cannot handshake with the embedded controller or jump to the BIOS via SMIs. However, the fact that AML code spins forever means that lockup conditions are not being checked for in the AML bytecode. Test 87 of 93: Check _BCL (Query List of Brightness Control Levels Supported). Package has 2 elements: 00: INTEGER: 0x00000000 01: INTEGER: 0x00000000 FAILED [MEDIUM] Method_BCLElementCount: Test 87, Method _BCL should return a package of more than 2 integers, got just 2. Test 88 of 93: Check _BCM (Set Brightness Level). ACPICA Exception AE_AML_PACKAGE_LIMIT during execution of method _BCM FAILED [CRITICAL] AEAMLPackgeLimit: Test 88, Detected error 'Package limit' when evaluating '\_SB_.PCI0.GFX0.DD02._BCM'. ==================================================================================================== ACPI table settings sanity checks. ---------------------------------------------------------------------------------------------------- Test 1 of 1: Check ACPI tables. PASSED: Test 1, Table APIC passed. Table ECDT not present to check. FAILED [MEDIUM] FADT32And64BothDefined: Test 1, FADT 32 bit FIRMWARE_CONTROL is non-zero, and X_FIRMWARE_CONTROL is also non-zero. Section 5.2.9 of the ACPI specification states that if the FIRMWARE_CONTROL is non-zero then X_FIRMWARE_CONTROL must be set to zero. ADVICE: The FADT FIRMWARE_CTRL is a 32 bit pointer that points to the physical memory address of the Firmware ACPI Control Structure (FACS). There is also an extended 64 bit version of this, the X_FIRMWARE_CTRL pointer that also can point to the FACS. Section 5.2.9 of the ACPI specification states that if the X_FIRMWARE_CTRL field contains a non zero value then the FIRMWARE_CTRL field *must* be zero. This error is also detected by the Linux kernel. If FIRMWARE_CTRL and X_FIRMWARE_CTRL are defined, then the kernel just uses the 64 bit version of the pointer. PASSED: Test 1, Table HPET passed. PASSED: Test 1, Table MCFG passed. PASSED: Test 1, Table RSDT passed. PASSED: Test 1, Table RSDP passed. Table SBST not present to check. PASSED: Test 1, Table XSDT passed. ==================================================================================================== Re-assemble DSDT and find syntax errors and warnings. ---------------------------------------------------------------------------------------------------- Test 1 of 2: Disassemble and reassemble DSDT FAILED [HIGH] AMLAssemblerError4043: Test 1, Assembler error in line 2261 Line | AML source ---------------------------------------------------------------------------------------------------- 02258| 0x00000000, // Range Minimum 02259| 0xFEDFFFFF, // Range Maximum 02260| 0x00000000, // Translation Offset 02261| 0x00000000, // Length | ^ | error 4043: Invalid combination of Length and Min/Max fixed flags 02262| ,, _Y0E, AddressRangeMemory, TypeStatic) 02263| DWordMemory (ResourceProducer, PosDecode, MinFixed, MaxFixed, Cacheable, ReadWrite, 02264| 0x00000000, // Granularity ==================================================================================================== ADVICE: (for error #4043): This occurs if the length is zero and just one of the resource MIF/MAF flags are set, or the length is non-zero and resource MIF/MAF flags are both set. These are illegal combinations and need to be fixed. See section 6.4.3.5 Address Space Resource Descriptors of version 4.0a of the ACPI specification for more details. FAILED [HIGH] AMLAssemblerError4050: Test 1, Assembler error in line 2268 Line | AML source ---------------------------------------------------------------------------------------------------- 02265| 0xFEE01000, // Range Minimum 02266| 0xFFFFFFFF, // Range Maximum 02267| 0x00000000, // Translation Offset 02268| 0x011FEFFF, // Length | ^ | error 4050: Length is not equal to fixed Min/Max window 02269| ,, , AddressRangeMemory, TypeStatic) 02270| }) 02271| Method (_CRS, 0, Serialized) ==================================================================================================== ADVICE: (for error #4050): The minimum address is greater than the maximum address. This is illegal. FAILED [HIGH] AMLAssemblerError1104: Test 1, Assembler error in line 8885 Line | AML source ---------------------------------------------------------------------------------------------------- 08882| Method (_DIS, 0, NotSerialized) 08883| { 08884| DSOD (0x02) 08885| Return (0x00) | ^ | warning level 0 1104: Reserved method should not return a value (_DIS) 08886| } 08887| 08888| Method (_SRS, 1, NotSerialized) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1104: Test 1, Assembler error in line 9195 Line | AML source ---------------------------------------------------------------------------------------------------- 09192| Method (_DIS, 0, NotSerialized) 09193| { 09194| DSOD (0x01) 09195| Return (0x00) | ^ | warning level 0 1104: Reserved method should not return a value (_DIS) 09196| } 09197| 09198| Method (_SRS, 1, NotSerialized) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1127: Test 1, Assembler error in line 9242 Line | AML source ---------------------------------------------------------------------------------------------------- 09239| CreateWordField (CRES, \_SB.PCI0.LPCB.SIO.LPT0._CRS._Y21._MAX, MAX2) 09240| CreateByteField (CRES, \_SB.PCI0.LPCB.SIO.LPT0._CRS._Y21._LEN, LEN2) 09241| CreateWordField (CRES, \_SB.PCI0.LPCB.SIO.LPT0._CRS._Y22._INT, IRQ0) 09242| CreateWordField (CRES, \_SB.PCI0.LPCB.SIO.LPT0._CRS._Y23._DMA, DMA0) | ^ | warning level 0 1127: ResourceTag smaller than Field (Tag: 8 bits, Field: 16 bits) 09243| If (RLPD) 09244| { 09245| Store (0x00, Local0) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1128: Test 1, Assembler error in line 18682 Line | AML source ---------------------------------------------------------------------------------------------------- 18679| Store (0x01, Index (DerefOf (Index (Local0, 0x02)), 0x01)) 18680| If (And (WDPE, 0x40)) 18681| { 18682| Wait (\_SB.BEVT, 0x10) | ^ | warning level 0 1128: Result is not used, possible operator timeout will be missed 18683| } 18684| 18685| Store (BRID, Index (DerefOf (Index (Local0, 0x02)), 0x02)) ==================================================================================================== ADVICE: (for warning level 0 #1128): The operation can possibly timeout, and hence the return value indicates an timeout error. However, because the return value is not checked this very probably indicates that the code is buggy. A possible scenario is that a mutex times out and the code attempts to access data in a critical region when it should not. This will lead to undefined behaviour. This should be fixed. Table DSDT (0) reassembly: Found 2 errors, 4 warnings. Test 2 of 2: Disassemble and reassemble SSDT PASSED: Test 2, SSDT (0) reassembly, Found 0 errors, 0 warnings. FAILED [HIGH] AMLAssemblerError1104: Test 2, Assembler error in line 60 Line | AML source ---------------------------------------------------------------------------------------------------- 00057| { 00058| Store (CPDC (Arg0), Local0) 00059| GCAP (Local0) 00060| Return (Local0) | ^ | warning level 0 1104: Reserved method should not return a value (_PDC) 00061| } 00062| 00063| Method (_OSC, 4, NotSerialized) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1104: Test 2, Assembler error in line 174 Line | AML source ---------------------------------------------------------------------------------------------------- 00171| { 00172| Store (\_PR.CPU0.CPDC (Arg0), Local0) 00173| GCAP (Local0) 00174| Return (Local0) | ^ | warning level 0 1104: Reserved method should not return a value (_PDC) 00175| } 00176| 00177| Method (_OSC, 4, NotSerialized) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1104: Test 2, Assembler error in line 244 Line | AML source ---------------------------------------------------------------------------------------------------- 00241| { 00242| Store (\_PR.CPU0.CPDC (Arg0), Local0) 00243| GCAP (Local0) 00244| Return (Local0) | ^ | warning level 0 1104: Reserved method should not return a value (_PDC) 00245| } 00246| 00247| Method (_OSC, 4, NotSerialized) ==================================================================================================== FAILED [HIGH] AMLAssemblerError1104: Test 2, Assembler error in line 290 Line | AML source ---------------------------------------------------------------------------------------------------- 00287| { 00288| Store (\_PR.CPU0.CPDC (Arg0), Local0) 00289| GCAP (Local0) 00290| Return (Local0) | ^ | warning level 0 1104: Reserved method should not return a value (_PDC) 00291| } 00292| 00293| Method (_OSC, 4, NotSerialized) ==================================================================================================== Table SSDT (1) reassembly: Found 0 errors, 4 warnings. PASSED: Test 2, SSDT (2) reassembly, Found 0 errors, 0 warnings. PASSED: Test 2, SSDT (3) reassembly, Found 0 errors, 0 warnings. ==================================================================================================== 3 passed, 10 failed, 0 warnings, 0 aborted, 0 skipped, 0 info only. ==================================================================================================== Critical failures: 1 method test, at 1 log line: 1449: Detected error 'Package limit' when evaluating '\_SB_.PCI0.GFX0.DD02._BCM'. High failures: 11 klog test, at 1 log line: 121: HIGH Kernel message: [ 3.512783] ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0._DOD] (Node f7425858), AE_AML_PACKAGE_LIMIT (20110623/psparse-536) syntaxcheck test, at 1 log line: 1668: Assembler error in line 2261 syntaxcheck test, at 1 log line: 1687: Assembler error in line 2268 syntaxcheck test, at 1 log line: 1703: Assembler error in line 8885 syntaxcheck test, at 1 log line: 1716: Assembler error in line 9195 syntaxcheck test, at 1 log line: 1729: Assembler error in line 9242 syntaxcheck test, at 1 log line: 1742: Assembler error in line 18682 syntaxcheck test, at 1 log line: 1766: Assembler error in line 60 syntaxcheck test, at 1 log line: 1779: Assembler error in line 174 syntaxcheck test, at 1 log line: 1792: Assembler error in line 244 syntaxcheck test, at 1 log line: 1805: Assembler error in line 290 Medium failures: 9 mtrr test, at 1 log line: 76: Memory range 0xc0000000 to 0xdfffffff (PCI Bus 0000:00) has incorrect attribute Write-Combining. mtrr test, at 1 log line: 78: Memory range 0xfee01000 to 0xffffffff (PCI Bus 0000:00) has incorrect attribute Write-Protect. msr test, at 1 log line: 165: MSR SYSENTER_ESP (0x175) has 1 inconsistent values across 2 CPUs for (shift: 0 mask: 0xffffffffffffffff). msr test, at 1 log line: 173: MSR MISC_ENABLE (0x1a0) has 1 inconsistent values across 2 CPUs for (shift: 0 mask: 0x400c51889). wmi test, at 1 log line: 528: GUID 2B814318-4BE8-4707-9D84-A190A859B5D0 is unknown to the kernel, a driver may need to be implemented for this GUID. method test, at 1 log line: 1002: \_SB_.PCI0.LPCB.SIO_.COM1._DIS returned values, but was expected to return nothing. method test, at 1 log line: 1011: \_SB_.PCI0.LPCB.SIO_.LPT0._DIS returned values, but was expected to return nothing. method test, at 1 log line: 1443: Method _BCL should return a package of more than 2 integers, got just 2. acpitables test, at 1 log line: 1643: FADT 32 bit FIRMWARE_CONTROL is non-zero, and X_FIRMWARE_CONTROL is also non-zero. Se

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Part 2: The Customization Lifecycle

- by volker.eckardt(at)oracle.com

To understand the challenges when working with Customizations better, please allow me to explain my understanding from the Customization Lifecycle. The starting point is the functional GAP list. Any GAP can lead to a customization (but not have to). The decision is driven by priority, gain, costs, future functionality, accepted workarounds etc. Let's assume the customization has been accepted as such - including estimation. (Otherwise this blog would not have any value)Now the customization life-cycle starts and could look like this:- Functional specification- Technical specification- Technical development- Functional setup- Module Test- System Test- Integration Test (if required)- Acceptance Test- Production mode- Usage- 10 x Rework- 10 x Retest - 2 x Upgrade- 2 x Upgrade Test- Usage- 10 x Rework- 10 x Retest - 1 x Upgrade- 1 x Upgrade Test- Usage- Review for Retirement- Accepted Retirement- De-installationWhat I like to highlight herewith is that any material and documentation you create upfront or during the first phases will usually be used multiple times, partial or complete, will be enhanced, reviewed, retested. The better the quality right from the beginning is, the better we can perform the next steps.What I see very often is the wish to remove a customization, our customers are upgrading and they like to get at least some of the customizations replaced with standard functionality. To be able to support this process best, the customization documentation should contain at least the following key information: What is/are the business process(es) where this customization is used or linked to?Who was involved in the different customization phases?What are the objects comprising the customization?What is the setup necessary for the customization?What setup comes with the customization, what has to be done via other tools or manually?What are the test steps and test results (in all test areas)?What are linked customizations? What is the customization complexity?How is this customization classified?Which technologies were used?How many days were needed to create/test/upgrade the customization?Etc.If all this is available, a replacement / retirement can be done much more efficient and precise, or an estimation and upgrade itself can be executed with much better support.In the following blog entries I will explain in more detail why we suggest tracking such information, by whom this task shall be done and how.Volker Eckardt

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Microsoft Access: Customize Forms and Reports

Our Microsoft application guru Helen Bradley explains how to make Access database forms and reports more functional and attractive.

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JavaScript Class Patterns

- by Liam McLennan

To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created - so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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JavaScript Class Patterns

- by Liam McLennan

To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created - so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var john = new Person("John Galt", 50); console.log(john.toString()); var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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