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• Why is my mdadm raid-1 recovery so slow?

  - by dimmer

  On a system I'm running Ubuntu 10.04. My raid-1 restore started out fast but quickly became ridiculously slow (at this rate the restore will take 150 days!): dimmer@paimon:~$ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdc1[2] sdb1[1] 1953513408 blocks [2/1] [_U] [====>................] recovery = 24.4% (477497344/1953513408) finish=217368.0min speed=113K/sec unused devices: <none> Eventhough I have set the kernel variables to reasonably quick values: dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_min 1000000 dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_max 100000000 I am using 2 2.0TB Western Digital Hard Disks, WDC WD20EARS-00M and WDC WD20EARS-00J. I believe they have been partitioned such that their sectors are aligned. dimmer@paimon:/sys$ sudo parted /dev/sdb GNU Parted 2.2 Using /dev/sdb Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00M (scsi) Disk /dev/sdb: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 (parted) unit s (parted) p Number Start End Size File system Name Flags 1 2048s 3907028991s 3907026944s ext4 (parted) q dimmer@paimon:/sys$ sudo parted /dev/sdc GNU Parted 2.2 Using /dev/sdc Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00J (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/4096B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 I am beginning to think that I have a hardware problem, otherwise I can't imagine why the mdadm restore should be so slow. I have done a benchmark on /dev/sdc using Ubuntu's disk utility GUI app, and the results looked normal so I know that sdc has the capability to write faster than this. I also had the same problem on a similar WD drive that I RMAd because of bad sectors. I suppose it's possible they sent me a replacement with bad sectors too, although there are no SMART values showing them yet. Any ideas? Thanks. As requested, output of top sorted by cpu usage (notice there is ~0 cpu usage). iowait is also zero which seems strange: top - 11:35:13 up 2 days, 9:40, 3 users, load average: 2.87, 2.58, 2.30 Tasks: 142 total, 1 running, 141 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3096304k total, 1482164k used, 1614140k free, 617672k buffers Swap: 1526132k total, 0k used, 1526132k free, 535416k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 45 root 20 0 0 0 0 S 0 0.0 2:17.02 scsi_eh_0 1 root 20 0 2808 1752 1204 S 0 0.1 0:00.46 init 2 root 20 0 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/0 4 root 20 0 0 0 0 S 0 0.0 0:00.17 ksoftirqd/0 5 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/1 ... dmesg errors, definitely looking like hardware: [202884.000157] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [202884.007015] ata5.00: failed command: FLUSH CACHE EXT [202884.013728] ata5.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0 [202884.013730] res 40/00:00:ff:59:2e/00:00:35:00:00/e0 Emask 0x4 (timeout) [202884.033667] ata5.00: status: { DRDY } [202884.040329] ata5: hard resetting link [202889.400050] ata5: link is slow to respond, please be patient (ready=0) [202894.048087] ata5: COMRESET failed (errno=-16) [202894.054663] ata5: hard resetting link [202899.412049] ata5: link is slow to respond, please be patient (ready=0) [202904.060107] ata5: COMRESET failed (errno=-16) [202904.066646] ata5: hard resetting link [202905.840056] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [202905.849178] ata5.00: configured for UDMA/133 [202905.849188] ata5: EH complete [203899.000292] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [203899.007096] ata5.00: failed command: IDENTIFY DEVICE [203899.013841] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [203899.013843] res 40/00:00:ff:f9:f6/00:00:38:00:00/e0 Emask 0x4 (timeout) [203899.041232] ata5.00: status: { DRDY } [203899.048133] ata5: hard resetting link [203899.816134] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [203899.826062] ata5.00: configured for UDMA/133 [203899.826079] ata5: EH complete [204375.000200] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204375.007421] ata5.00: failed command: IDENTIFY DEVICE [204375.014799] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204375.014800] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204375.044374] ata5.00: status: { DRDY } [204375.051842] ata5: hard resetting link [204380.408049] ata5: link is slow to respond, please be patient (ready=0) [204384.440076] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204384.449938] ata5.00: configured for UDMA/133 [204384.449955] ata5: EH complete [204395.988135] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204395.988140] ata5.00: failed command: IDENTIFY DEVICE [204395.988147] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204395.988149] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204395.988151] ata5.00: status: { DRDY } [204395.988156] ata5: hard resetting link [204399.320075] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204399.330487] ata5.00: configured for UDMA/133 [204399.330503] ata5: EH complete

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• Use cURL with multiple POSTs

  - by Austin

  I'm trying to use cURL to download the contents of webpages that require forms to get to. In a browser it looks something like this 1.) Login using POST 2.) Pick which page to go to using another POST 3.) Pick another page... using POST 4.) etc.. until I get to the page I want, then download all textfiles linked to on that page. I am attempting to do this using a bash script and some loops with the values that change for each POST. My problem is how do I do multiple POSTs with cURL? Must there be cookies involved? FYI the website is http://metagenomics.nmpdr.org/ (MG-RAST).

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• At what point would you drop some of your principles of software development for the sake of more money?

  - by MeshMan

  I'd like to throw this question out there to interestingly see where the medium is. I'm going to admit that in my last 12 months, I picked up TDD and a lot of the Agile values in software development. I was so overwhelmed with how much better my development of software became that I would never drop them out of principle. Until...I was offered a contracting role that doubled my take home pay for the year. The company I joined didn't follow any specific methodology, the team hadn't heard of anything like code smells, SOLID, etc., and I certainly wasn't going to get away with spending time doing TDD if the team had never even seen unit testing in practice. Am I a sell out? No, not completely... Code will always been written "cleanly" (as per Uncle Bob's teachings) and the principles of SOLID will always be applied to the code that I write as they are needed. Testing was dropped for me though, the company couldn't afford to have such a unknown handed to the team who quite frankly, even I did create test frameworks, they would never use/maintain the test framework correctly. Using that as an example, what point would you say a developer should never drop his craftsmanship principles for the sake of money/other benefits to them personally? I understand that this can be a very personal opinion on how concerned one is to their own needs, business needs, and the sake of craftsmanship etc. But one can consider that for example testing can be dropped if the company decided they would rather have a test team, than rather understand unit testing in programming, would that be something you could forgive yourself for like I did? So given that there is something you would drop, there usually should be an equal cost in the business that makes up for what you drop - hopefully, unless of course you are pretty much out for lining your own pockets and not community/social collaborating ;). Double your money, go back to RAD? Or walk on, and look for someone doing Agile, and never look back...

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• Libgdx ParallaxScrolling and TiledMaps

  - by kirchhoff

  I implemented ParallaxScrolling for my SideScroller project, everything is working but the tiled map (the most important part!). I've been trying out everything but it doesn't work (see the code below). I'm using ParallaxCamera from GdxTests, it's working perfectly for the background layers. I can't explain myself properly in english, so I recorded 2 videos: Before parallaxScrolling After parallaxScrolling As you can see, now the platforms appear in the middle of the Y-axis. I've got a Map class with 2 tiled maps, so I need two renderers too: private TiledMapRenderer renderer1; private TiledMapRenderer renderer2; public void update(GameCamera camera) { renderer1.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); renderer2.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); } In bold, the code I think I should change. I've tried changing parameters, even adding hardcoded values, etc, but one of two: 1. Nothing happens. 2. Platforms disappear. Here is some aditional code. The render method: world.update(delta); parallaxBackground.update(camera); clear(0.5f, 0.7f, 1.0f, 1); batch.setProjectionMatrix(camera.calculateParallaxMatrix(0, 0)); batch.disableBlending(); batch.begin(); batch.draw(background, -(int)background.getRegionWidth()/2, -(int)background.getRegionHeight()/2); batch.end(); batch.enableBlending(); parallaxBackground.draw(batch, camera); renderer.render(batch);

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• Copying Metadata Between Files in iTunes

  - by Levi Hackwith

  A while back, I converted some AVI files to .m4v files that would be playable on my iPhone. When I play these files on my PC using iTunes the quality is terrible because the resolution is so low. My solution is to convert the AVI's using Handbrake using the "Universal" preset; it works like a charm and I can now watch them both on my PC and iPhone. The Problem I want to import the newly converted files into my iTunes library and be able to copy the metadata (show, season (these are TV episodes) Description, etc) without having to manually copy and paste values from one file to another. Is it possible to just say "copy this file's metadata to this file"?

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• C Programming matrix

  - by Bilal Khan

  In this program the user enters the # of columns of the matrix and then the entries of the matrix. So, for example, if the user enters 2 for column # and 1 2 3 4 for entries then the program develops a 2 by 2 matrix with 1 2 3 4 as entries. My program works perfectly in such a case. However, if the user for example had only entered 1 2 3 then my program makes a matrix with garbage values. I would like the program in such a case to exit the program. It is a simple question, but it has me baffled. #include<stdio.h> #include<stdlib.h> int main() { int m,x, n, c = 0, d,k, matrix[10][10], transpose[10][10], product[10][10]; printf("Enter the number of columns of matrix "); scanf("%d",&m); if(m<=0){ printf("You entered a invalid value."); exit(0); } else{ printf("Enter the elements of matrix \n"); for( c = 0 ; c < 10 ; c++ ) { for( d = 0 ; d < m ; d++ ) { scanf("%d",&matrix[c][d]); if (matrix[c][d] == 99) // 'x' is character variable I declared to use as a break break; // c = c+1; } if (matrix[c][d] == 99) break; } } printf("\nHere is your matrix:\n"); int i; for(i=0;i<c;i++) { for(d=0;d<m;d++) { printf("%3d ",matrix[i][d]); } printf("\n"); }

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• approx via inetd is not open to connection for others machines

  - by Cédric Girard

  I have an approx server to speed up Debian apt updates, on my Ubuntu 11.04 desktop PC, it had ran fine in the past, but today le 9999 port is open from localhost, but not for others PC. I have not modified inetd configuration at all. What can I check and try? inetd.conf 9999 stream tcp nowait approx /usr/sbin/approx /usr/sbin/approx approx.com # Here are some examples of remote repository mappings. # See http://www.debian.org/mirror/list for mirror sites. debian http://ftp2.fr.debian.org/debian security http://security.debian.org/debian-security volatile http://volatile.debian.org/debian-volatile # The following are the default parameter values, so there is # no need to uncomment them unless you want a different value. # See approx.conf(5) for details. $cache /espace/Dossiers/approx $max_rate unlimited $max_redirects 5 $user approx $group approx $syslog daemon $pdiffs true $offline false $max_wait 10 $verbose false $debug false I tried to allow others PC to connect with a "ALL: ALL" in hosts.allow. ufw is disabled, iptables-save is empty.

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• Regulating how much to draw based on how much was drawn last frame.

  - by Mike Howard

  I have a 3D game world on an iPhone (limited graphics speed), and I'm already regulating whether I draw each shape on the screen based on it's size and distance from the camera. Something like... if (how_big_it_looks_from_the_camera > constant) then draw What I want to do now is also take into account how many shapes are being drawn, so that in busier areas of the game world I can draw less than I otherwise would. I tried to do this by dividing how_big_it_looks by the number of shapes that were drawn last frame (well, the square root of this but I'm simplifying - the problem is the same). if (how_big_it_looks / shapes_drawn > constant2) then draw But the check happens at the level of objects which represent many drawn shapes, and if an object containing many shapes is switched on, it increases shapes_drawn lots and switches itself back off the next frame. It flickers on and off. I tried keeping a kind of weighted average of previous values, by each frame doing something like shapes_drawn_recently = 0.9 * shapes_drawn_recently + 0.1 * shapes_just_drawn, but of course it only slows the flickering down because of the nature of the feedback loop. Is there a good way of solving this? My project is in Objective-C, but a general algorithm or pseudo-code is good too. Thanks.

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• Prevent registry changes by users

  - by graf_ignotiev

  Background: I run a small computer lab of 10 computers using Windows 7 x64 Enterprise. Our users are set up as limited users. For additional restrictions, I set up local group policy for non-administrators using the microsoft management console. Problem: Recently, I found out that some of these restrictions had been removed. Reviewing the settings MMC and in ntuser.pol showed that the settings should still be in place. However, the related registry settings were missing in ntuser.dat. I already have registry editing disabled in the GPO (though not in silent mode). Question: What is the best way to deal with this situation? Should I look into preventing registry setting changes? Should I set up registry auditing to found out how these keys are getting changed in the first place? Or should I give up the ghost and write some kind of logon script that enforces registry values if they've been change? Any other ideas?

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• Do you store mysql exports in your version control tool for reverting to in event of error?

  - by Rob

  We run an internal web server with in-house software to run a manufacturing line. When new product features are to be added, either or both of the following occur: changes to the in-house server software may be required to support these - these are for significant changes in functionality, being code drive. changes to the MySQL database for new entries for the part numbers, these are for smaller changes, configurations, changes to already existing values and parameters -- such changes don't require code changes. Ideally we'd want our changes to be here rather than in item 1. Item 1 is version controlled in Subversion, so previous revisions can be referred to for rolling back to in the event of problems introduced in the latest revision. But what about changes to the MySQL database? We have quality processes to ensure that such changes are error-free but there is always a chance that errors can pass through, e.g. mistake in data entry or faults with the code that uses the MySQL corrupting the database etc. We have a automated backup every 6 hours but what if we want more manual defined checkpoints in between these intervals, we could use the same backup system but I wondered if folks here used other methods to store previous states of databases, e.g. exporting the database as a plain text SQL dump -- at least with this method it would be possible to see diffs e.g. in Beyond Compare for trouble shooting. Thoughts?

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• Segmentation Fault with mod_include

  - by Benedikt Eger

  Hi, I'm using a rather complex structure with multiple ssi-includes, set- and echo-commands. The first document writes a lot of set-commands, includes another document which then again includes a third document. On the last included document the variable values are printed using the echo-command. I noticed that with an increasing number of variables the probability for a segmentation fault to happen rises. Did anyone experience something similar? How do I go about debugging such a problem? I'm using IBM_HTTP_Server/2.0.47.1-PK65782 Apache/2.0.47

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• Analyzing Memory Usage: Java vs C++ Negligible?

  - by Anthony

  How does the memory usage of an integer object written in Java compare\contrast with the memory usage of a integer object written in C++? Is the difference negligible? No difference? A big difference? I'm guessing it's the same because an int is an int regardless of the language (?) The reason why I asked this is because I was reading about the importance of knowing when a program's memory requirements will prevent the programmer from solving a given problem. What fascinated me is the amount of memory required for creating a single Java object. Take for example, an integer object. Correct me if I'm wrong but a Java integer object requires 24 bytes of memory: 4 bytes for its int instance variable 16 bytes of overhead (reference to the object's class, garbage collection info & synchronization info) 4 bytes of padding As another example, a Java array (which is implemented as an object) requires 48+bytes: 24 bytes of header info 16 bytes of object overhead 4 bytes for length 4 bytes for padding plus the memory needed to store the values How do these memory usages compare with the same code written in C++? I used to be oblivious about the memory usage of the C++ and Java programs I wrote, but now that I'm beginning to learn about algorithms, I'm having a greater appreciation for the computer's resources.

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• Get to Know a Candidate (6 of 25): Jill Stein&ndash;Green Party

  - by Brian Lanham

  DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Stein is a physician with degrees from Harvard College and Harvard Medical School.  She serves on the boards of Greater Boston Physicians for Social Responsibility and MassVoters for Fair Elections, and has been active with the Massachusetts Coalition for Healthy Communities Jill Stein advocates a "Green New Deal" in which renewable energy jobs would be created to address climate change and environmental issues with the objective of employing "every American willing and able to work". Citing the research of Dr. Phillip Harvey, Professor of Law & Economics at Rutgers University, as evidence of the successful economic effects of the 1930s' New Deal projects, Stein would fund the plan with a 30% reduction in the U.S. military budget, returning US troops home, and increasing taxes on areas such as capital gains, offshore tax havens and multimillion dollar real estate. Stein plans on impacting what she sees as a growing convergence of environmental crises in water, soil, fisheries and forests, through the creation of sustainable infrastructure based in clean renewable energy generation and sustainable communities principles such as increasing intra-city mass transit and inter-city railroads, creating 'complete streets' that safely encourage bike and pedestrian traffic and regional food systems based on sustainable organic agriculture The Green Party of the United States was founded in 1991 as a voluntary association of state green parties. With its founding, the Green Party of the United States became the primary national Green organization in the United States, eclipsing the Greens/Green Party USA, which emphasized non-electoral movement building. The Green Party of the United States of America emphasizes environmentalism, non-hierarchical participatory democracy, social justice, respect for diversity, peace and nonviolence. Their "Ten Key Values," which are described as non-authoritative guiding principles, are as follows: Grassroots democracy Social justice and equal opportunity Ecological wisdom Nonviolence Decentralization Community-based economics Feminism and gender equality Respect for diversity Personal and global responsibility Future focus and sustainability The Green Party does not accept donations from corporations. Thus, the party's platforms and rhetoric critique any corporate influence and control over government, media, and American society at large. Stein has access to 403 electoral votes and is a write-in candidate in GA, IN, and MS Learn more about Jill Stein and Green Party on Wikipedia.

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• SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2

  - by pinaldave

  Yesterday I wrote a real world story of how a friend who thought they have an issue with intrusion or virus whereas the issue was really in the code. I strongly suggest you read my earlier blog post Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 before continuing this blog post as this is second part of the first blog post. Let me reproduce the simple scenario in T-SQL. Building Sample Data USE [TestDB] GO -- Creating Table Products CREATE TABLE [dbo].[Products]( [ProductID] [int] NOT NULL, [ProductDesc] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )) ON [PRIMARY] GO -- Creating Table ProductDetails CREATE TABLE [dbo].[ProductDetails]( [ProductDetailID] [int] NOT NULL, [ProductID] [int] NOT NULL, [Total] [int] NOT NULL, CONSTRAINT [PK_ProductDetails] PRIMARY KEY CLUSTERED ( [ProductDetailID] ASC )) ON [PRIMARY] GO ALTER TABLE [dbo].[ProductDetails] WITH CHECK ADD CONSTRAINT [FK_ProductDetails_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Products] ([ProductID]) ON UPDATE CASCADE ON DELETE CASCADE GO -- Insert Data into Table USE TestDB GO INSERT INTO Products (ProductID, ProductDesc) SELECT 1, 'Bike' UNION ALL SELECT 2, 'Car' UNION ALL SELECT 3, 'Books' GO INSERT INTO ProductDetails ([ProductDetailID],[ProductID],[Total]) SELECT 1, 1, 200 UNION ALL SELECT 2, 1, 100 UNION ALL SELECT 3, 1, 111 UNION ALL SELECT 4, 2, 200 UNION ALL SELECT 5, 3, 100 UNION ALL SELECT 6, 3, 100 UNION ALL SELECT 7, 3, 200 GO Select Data from Tables -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Delete Data from Products Table -- Deleting Data DELETE FROM Products WHERE ProductID = 1 GO Select Data from Tables Again -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Clean up Data -- Clean up DROP TABLE ProductDetails DROP TABLE Products GO My friend was confused as there was no delete was firing over ProductsDetails Table still there was a delete happening. The reason was because there is a foreign key created between Products and ProductsDetails Table with the keywords ON DELETE CASCADE. Due to ON DELETE CASCADE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. Workaround 1: Design Changes – 3 Tables Change the design to have more than two tables. Create One Product Mater Table with all the products. It should historically store all the products list in it. No products should be ever removed from it. Add another table called Current Product and it should contain only the table which should be visible in the product catalogue. Another table should be called as ProductHistory table. There should be no use of CASCADE keyword among them. Workaround 2: Design Changes - Column IsVisible You can keep the same two tables. 1) Products and 2) ProductsDetails. Add a column with BIT datatype to it and name it as a IsVisible. Now change your application code to display the catalogue based on this column. There should be no need to delete anything. Workaround 3: Bad Advices (Bad advises begins here) The reason I have said bad advices because these are going to be bad advices for sure. You should make necessary design changes and not use poor workarounds which can damage the system and database integrity further. Here are the examples 1) Do not delete the data – well, this is not a real solution but can give time to implement design changes. 2) Do not have ON CASCADE DELETE – in this case, you will have entry in productsdetails which will have no corresponding product id and later on there will be lots of confusion. 3) Duplicate Data – you can have all the data of the product table move to the product details table and repeat them at each row. Now remove CASCADE code. This will let you delete the product table rows without any issue. There are so many things wrong this suggestion, that I will not even start here. (Bad advises ends here)  Well, did I miss anything? Please help me with your suggestions. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Misconceptions about purely functional languages?

  - by Giorgio

  I often encounter the following statements / arguments: Pure functional programming languages do not allow side effects (and are therefore of little use in practice because any useful program does have side effects, e.g. when it interacts with the external world). Pure functional programming languages do not allow to write a program that maintains state (which makes programming very awkward because in many application you do need state). I am not an expert in functional languages but here is what I have understood about these topics until now. Regarding point 1, you can interact with the environment in purely functional languages but you have to explicitly mark the code (functions) that introduces them (e.g. in Haskell by means of monadic types). Also, AFAIK computing by side effects (destructively updating data) should also be possible (using monadic types?) but is not the preferred way of working. Regarding point 2, AFAIK you can represent state by threading values through several computation steps (in Haskell, again, using monadic types) but I have no practical experience doing this and my understanding is rather vague. So, are the two statements above correct in any sense or are they just misconceptions about purely functional languages? If they are misconceptions, how did they come about? Could you write a (possibly small) code snippet illustrating the Haskell idiomatic way to (1) implement side effects and (2) implement a computation with state?

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• CodePlex Daily Summary for Sunday, June 17, 2012

  CodePlex Daily Summary for Sunday, June 17, 2012Popular ReleasesXDA ROM Hub: XDA ROM Hub v0.35 Beta: Download and install stock ROM -- Not all ROMS are online. Flash CWM On locked bootloader. Root. Unroot. Flash kernels. Flash system image Erase system. Erase boot. Erase Data and Cache. Install update.zip. Install ROM addons. Install Boot animations. Unlock bootloader. Please rate and reviewCodename 'Chrometro': Developer Preview: Welcome to the Codename 'Chrometro' Developer Preview! This is the very first public preview of the app. Please note that this is a highly primitive build and the app is not even half of what it is meant to be. The Developer Preview sports the following: 1) An easy to use application setup. 2) The Assistant which simplifies your task of customization. 3) The partially complete Metro UI. 4) A variety of settings 5) A partially complete web browsing experience To get started, download the Ins...Cosmos (C# Open Source Managed Operating System): Release 92560: Prerequisites Visual Studio 2010 - Any version including Express. Express users must also install Visual Studio 2010 Integrated Shell runtime VMWare - Cosmos can run on real hardware as well as other virtualization environments but our default debug setup is configured for VMWare. VMWare Player (Free). or Workstation VMWare VIX API 1.11AutoUpdaterdotNET : Autoupdate for VB.NET and C# Developer: AutoUpdater.NET 1.1: Release Notes *New feature added that allows user to select remind later interval.Sumzlib: API document: API documentMicrosoft SQL Server Product Samples: Database: AdventureWorks 2008 OLTP Script: Install AdventureWorks2008 OLTP database from script The AdventureWorks database can be created by running the instawdb.sql DDL script contained in the AdventureWorks 2008 OLTP Script.zip file. The instawdb.sql script depends on two path environment variables: SqlSamplesDatabasePath and SqlSamplesSourceDataPath. The SqlSamplesDatabasePath environment variable is set to the default Microsoft ® SQL Server 2008 path. You will need to change the SqlSamplesSourceDataPath environment variable to th...HigLabo: HigLabo_20120613: Bug fix HigLabo.Mail Decode header encoded by CP1252Jasc (just another script compressor): 1.3.1: Updated Ajax Minifier to 4.55.WipeTouch, a jQuery touch plugin: 1.2.0: Changes since 1.1.0: New: wipeMove event, triggered while moving the mouse/finger. New: added "source" to the result object. Bug fix: sometimes vertical wipe events would not trigger correctly. Bug fix: improved tapToClick handler. General code refactoring. Windows Phone 7 is not supported, yet! Its behaviour is completely broken and would require some special tricks to make it work. Maybe in the future...Phalanger - The PHP Language Compiler for the .NET Framework: 3.0.0.3026 (June 2012): Fixes: round( 0.0 ) local TimeZone name TimeZone search compiling multi-script-assemblies PhpString serialization DocDocument::loadHTMLFile() token_get_all() parse_url()BlackJumboDog: Ver5.6.4: 2012.06.13 Ver5.6.4 　(1) Web???????、???POST??????????????????CRM 2011 ERD Designer: CRM 2011 ERD Designer: CRM 2011 ERD Designer BETA version is now availableBumblebee: Version 0.3.1: Changed default config values to decent ones. Restricted visibility of Hive.fs to internal. Added some XML documentation. Added Array.shuffle utility. The dll is also available on NuGet My apologies, the initial source code referenced was missing one file which prevented it from building The source code contains two examples, one in C#, one in F#, illustrating the usage of the framework on the Travelling Salesman Problem: Source CodeSharePoint XSL Templates: SPXSLT 0.0.9: Added new template FixAmpersands. Fixed the contents of the MultiSelectValueCheck.xsl file, which was missing the stylesheet wrapper.ExcelFileEditor: .CS File: nothingWeapsy - ASP.NET MVC CMS: 1.0.0 RC: - Upgrade to Entity Framework 4.3.1 - Added AutoMapper custom version (by nopCommerce Team) - Added missed model properties and localization resources of Plugin Definitions - Minor changes - Fixed some bugsXenta Framework - extensible enterprise n-tier application framework: Xenta Framework 1.8.0 Beta: Catalog and Publication reviews and ratings Store language packs in data base Improve reporting system Improve Import/Export system A lot of WebAdmin app UI improvements Initial implementation of the WebForum app DB indexes Improve and simplify architecture Less abstractions Modernize architecture Improve, simplify and unify API Simplify and improve testing A lot of new unit tests Codebase refactoring and ReSharpering Utilize Castle Windsor Utilize NHibernate ORM ...Microsoft Ajax Minifier: Microsoft Ajax Minifier 4.55: Properly handle IE extension to CSS3 grammar that allows for multiple parameters to functional pseudo-class selectors. add new switch -braces:(new|same) that affects where opening braces are placed in multi-line output. The default, "new" puts them on their own new line; "same" outputs them at the end of the previous line. add new optional values to the -inline switch: -inline:(force|noforce), which can be combined with the existing boolean value via comma-separators; value "force" (which...Microsoft Media Platform: Player Framework: MMP Player Framework 2.7 (Silverlight and WP7): Additional DownloadsSMFv2.7 Full Installer (MSI) - This will install everything you need in order to develop your own SMF player application, including the IIS Smooth Streaming Client. It only includes the assemblies. If you want the source code please follow the link above. Smooth Streaming Sample Player - This is a pre-built player that includes support for IIS Smooth Streaming. You can configure the player to playback your content by simplying editing a configuration file - no need to co...Liberty: v3.2.1.0 Release 10th June 2012: Change Log -Added -Liberty is now digitally signed! If the certificate on Liberty.exe is missing, invalid, or does not state that it was developed by "Xbox Chaos, Open Source Developer," your copy of Liberty may have been altered in some (possibly malicious) way. -Reach Mass biped max health and shield changer -Fixed -H3/ODST Fixed all of the glitches that users kept reporting (also reverted the changes made in 3.2.0.2) -Reach Made some tag names clearer and more consistent between m...New ProjectsAir Sanity: its a Project for a Microsoft ContestAsp.Net Settings Checking: Simple page for review all settings for web application ASP.Net 2.0. Ex: email setting, MS SQL setting,...ATH Commander: Projekt tworzony na zaliczenie przedmiotuCold Flame Youtube Library: .net library to download youtube videos, get youtube video titles and rip audio from a youtube videoComponentModelEx: This project add functionalities to handle the INotifyPropertyChanged interface. It also includes a bit of the MVVM pattern.CRUD Services: Provides a single generic CRUD service that can handle CRUD operations for any entity. Includes wrappers for supporting backend frameworks like Entity Framework and Linq-To-Sql, as well as for communication stacks like WCF and ASP.NET Web API.DotNetNuke Persian Packages: ???? ????? ? ???? ??? ?? ???? ???? 6.1.5 ???? ????? ??? ?? ???? - ??? ?? ?? ??FactureManger: With Facture manager you can easily create products, users, business partners and add them into Factures. This application can help to any business. GetSP2010ListIDs: This application is most useful while performing a manual deployment or backup/restore of SP2010 sites/lists/libraries from one environment to anotherKTOP Homeworks: ???????? ??????? ?? ?????Minecraft Italian Utility: Applicazione originariamente pubblicata su minecraftitalia.net, qui ci saranno le release e gli aggiornamenti My_first_Codeplex_project: My first Codeplex projectOAuth .NET Client: This project implements an OAuth client library in C# .NET.Painter: Hello! This is the help file for the Painter program. With this file you will be introduced into the futures of the program and the secrets of the program. PDN C++ AMP Effects: Paint.NET Gaussian blur effect written in C++ AMPThe East Wedding: This is a website for the East WeddingXDesigner.Writer: .XDesigner.Writer is a Document Editor like MS Word , Written in 100% C# code , without any the 3th part component , without RTF Text box , MS Word component or

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• Java Applet Tower Defence Game needs tweeking

  - by Ephiras

  Hello :) i have made a tower defence Game for my computer science class as one of my major projects, but have encountered some rather fatal roadblocks. here they are creating a menu screen (class Menu) that can set the total number of enimies, the max number of towers, starting money and the map. i tried creating a constructor in my Main class that sets all the values to whatever the Menu class passes in. I want the Menu screen to close after a difficulty has been selected and the main class to begin. Another problem i would really like some help with is instead of having to write entire arrays i would like to create a small segment of code that runs through an entire picture and sets up an array based on that pixels color.this way i can have multiple levels just dragged into a level folder and have the program read through them. users can even create their own. so a 1 if its yellow, a two if blue and a 3 if purple, then everything else = 0; you can download all the classes and code uif you'd like here sorry about having to redirect you but i wasn't sure how to efficently add a code spoiler. help is greatly appreciated

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• Personal Software Process (PSP1)

  - by gentoo_drummer

  I'm trying to figure out an exercise but it doesn't really makes to much sense.. I'm not asking someone to provide the solution. just to try and analyse what needs to be done in order to solve this. I'm trying to understand which PSP 1.0 1.1 process I should use. PROBE? Or something else? I would greatly appreciate some help on this one from someone that has experience with the Personal Software Process Methodology.. Here is the question. For the reference case (“code1.c”), the following s/w metrics are provided: man-hours spent in implementation phase (per-module): 2,7 mh/file man-hours spent in testing phase (per-module): 4,3 mh/file estimated number of bugs remaining (per-module): 0,3 errors/function, 4 errors/module (remaining) Based on the corresponding values provided for the reference case, each of the following tasks focus on some s/w metrics to be estimated for the test case (“code2.c”): [25 marks] (estimated) man-hours required in implementation phase (per-module) [8 marks] (estimated) man-hours required in testing phase (per-module) [8 marks] (estimated) number of bugs remaining at the end of testing phase (per-module) [9 marks] Tasks 4 through 6 should use the data provided for the reference case within the context of Personal Software Process level-1 (PSP-1), using them as a single-point historic data log. Specifically, the same s/w metrics are to be estimated for the test case (“code2.c”), using PSP as the basic estimation model. In order to perform the above listed tasks, students are advised to consider all phases of the PSP software development process, especially at levels PSP0 and PSP1. Both cases are to be treated as separate case-studies in the context of classic s/w development.

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• Performing client-side OAuth authorized Twitter API calls versus server side, how much of a difference is there in terms of performance?

  - by Terence Ponce

  I'm working on a Twitter application in Ruby on Rails. One of the biggest arguments that I have with other people on the project is the method of calling the Twitter API. Before, everything was done on the server: OAuth login, updating the user's Twitter data, and retrieving tweets. Retrieving tweets was the heaviest thing to do since we don't store the tweets in our database, so viewing the tweets means that we have to call the API every time. One of the people in the project suggested that we call the tweets through Javascript instead to lessen the load on the server. We used GET search, which, correct me if I'm wrong, will be removed when v1.0 becomes completely deprecated, but that really isn't a concern now. When the Twitter API has migrated completely to v1.1 (again, correct me if I'm wrong), every calls to the API must be authenticated, so we have to authenticate our Javascript requests to the API. As said here: We don't support or recommend performing OAuth directly through Javascript -- it's insecure and puts your application at risk. The only acceptable way to perform it is if you kept all keys and secrets server-side, computed the OAuth signatures and parameters server side, then issued the request client-side from the server-generated OAuth values. If we do exactly what Twitter suggests, the only difference between this and doing everything server-side is that our server won't have to contact the Twitter API anymore every time the user wants to view tweets. Here's how I would picture what's happening every time the user makes a request: If we do it through Javascript, it would be harder on my part because I would have to create the signatures manually for every request, but I will gladly do it if the boost in performance is worth all the trouble. Doing it through Ruby on Rails would be very easy since the Twitter gem does most of the grunt work already, so I'm really encouraging the other people in the project to agree with me. Is the difference in performance trivial or is it significant enough to switch to Javascript?

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• Windows Server 2012 - SSL Cypher Suite Order Not Long Enough

  - by Sam

  I want to re-order the cypher suites on our new Windows Server 2012 box to help mitigate the BEAST vulnerability for our clients. I went to Local Group Policy => Computer Configuration => Administrative Templates => Network => SSL Configuration Settings, opened SSL Cypher Suite Order, enabled it, and copied the values from the SSL Cypher Suites textbox. I pasted them into notepad, re-ordered them, then copied+pasted them back into the SSL Cypher Suites textbox. However, the box isn't long enough to hold them all, despite the fact that the length didn't change. I would have to drop the last 3 cyphers (SSL_CK_DES_192_EDE3_CBC_WITH_MD5,TLS_RSA_WITH_NULL_SHA256,TLS_RSA_WITH_NULL_SHA) in order for it to fit. Should I just drop them? Other ideas?

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• In Nginx, can I handle both a location:url or a content-type: text/html response from memcached?

  - by Sean Foo

  I'm setting up an nginx - apache reverse proxy where nginx handles the static files and apache the dynamic. I have a search engine and depending on search parameter I either directly forward the user to the page they are looking for or provide a set of search results. I cache these results in memcached as key:/search.cgi?q=foo value: LOCATION:http://www.example.com/foo.html and key:/search.cgi?q=bar value: CONTENT-TYPE: text/html <html> .... .... </html> I can pull the "Content-type...." values out of memcached using nginx and send them to the user, but I can't quite figure out how to handle a returned value like "Location..." Can I?

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• Increase performance of Samsung 830 256GB SSD

  - by Robert Koritnik

  I have a Samsung 830 SSD in my notebook connected to a SATA interface. This is a rather old HP notebook nc8430 which means SATA is SATA I and not II or even III that disk supports. But SATA I still supports speeds up to 150MB/s so I expected at least double values as per image below. CrystalDiskMark shows rather slow performance: I've been using this SSD for over a year now and I would like to know what to do to make it blazingly fast as other reports say it should be? Edit As suggested I'm adding AS SSD screenshot of the test. And Samsung Magician's benchmark which is likely biased...

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• Transferring Conditional Formatting (without the cell value) in Excel

  - by london

  If I have 3 layers of conditional formatting in a cell (B2) is there a way of transferring the format of cell (B2) to another cell (A2) without copying across the value in the original cell (B2). I.e. in b2 I have conditional formatting dependent on what is selected from a drop down list of 4 options). I want the format to be copied across the the cell before this (A2) without the values being copied across. Essentially A2 has the title and B2 has the value but I would like the same formatting across both. I have manged to do it by setting A2 as ="Title "&B2 and applying conditional formatting to this. The spacing means the text from B2 doesn't show. This works but is really ugly. Is there a better way givern there ae too many conditions for a standard IF function. (if possible the solution should be windows 2003 compatible)

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• Ubuntu unstable, showing awkward behavior

  - by Christophe De Troyer

  Let me start off by saying that this problem can't be described in such a way that allows me to find other topics, which have some relevance to this problem. That's why I created this question. In case this question might have been asked before, I apologize. So what is the problem: My computer (Intel Core I5 2500K - with HD3000 graphics -, 6 gb DDR, 1 SSD, 3 HDD's and an Asus P8Z68 mobo) runs Windows on the SDD. But I decided to give Ubuntu a chance to be my daily OS for basic needs since it's open source and I find it a handicap of not being able to work with it. I decided to run the windows installer and install Ubuntu 12.04 to my 320 Gb hdd which was not being used in my computer. After installing it and booting it, it worked great! I spent the rest of the day/night using it, and falling for it. Great, today I booted Ubuntu (I had the choice in the bootloader as I expected). It asked me for my login and it started logging in. Now, after a few (literally) minutes of letting it "boot" I tried determining the cause of this. What I've figured out so far: When I left click on my desktop it freezes completely for a few seconds I have something like tearing in the left side menu (in games, you know) when I move my mouse around It runs well when just hovering around with my mouse, but from the point I click on something it freezes. What have I tried? I ran a HD Tune diagnostic on the HDD but the performance seems to be very close to the stock values, so I'm taking it as a good HDD. I'm trying to get to the drivers update panel for Ubuntu, but with the state it's in, it's taking a lot of time.. Could anyone point me in a direction for troubleshooting this? I'm not really a noob at all, just when using Linux.. :) Thanks in advance! Christophe,

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