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• Oracle Healthcare Data Warehouse Foundations RELEASED!

  - by Glen McCallum

  Since I joined Oracle I've been working on Oracle Healthcare Data Warehouse Foundations (OHDF). It was officially released earlier this month at HIMSS. But for over 2 months prior to that I had to keep it a secret. It was so tough; I didn't even tell my family when they asked me what I was working on. Anyway, OHDF is an enterprise healthcare data model. Unlike Healthcare Transaction Base, OHDF is in 3rd normal form. It is logical and reasonably easy to understand for anyone with some experience in the healthcare domain. OHDF is emerging as the core of Oracle's healthcare business intelligence applications.

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• Connecting to Microsoft Excel using Oracle Data Integrator

  - by julien.testut

  The posts in this series assume that you have some level of familiarity with ODI. The concepts of Topology, Data Server, Physical and Logical Architecture are used here assuming that you understand them in the context of ODI. If you need more details on these elements, please refer to the ODI Tutorial for a quick introduction, or to the complete ODI documentation for more details. In this post I will describe how a Microsoft Excel spreadsheet can be used in Oracle Data Integrator. Microsoft Excel is one of the many different technologies you can leverage in ODI as a source or as a target. Prepare your Excel spreadsheet Prior to using a Microsoft Excel spreadsheet in ODI we need to specify a name for the different cell tables we want to use. You can have multiple names in the same spreadsheet. First open up a Microsoft Excel spreadsheet, we will need to define a named range.

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• SQL SERVER – Find Weekend and Weekdays from Datetime in SQL Server 2012

  - by pinaldave

  Yesterday we had very first SQL Bangalore User Group meeting and I was asked following question right after the session. “How do we know if today is a weekend or weekday using SQL Server Functions?” Well, I assume most of us are using SQL Server 2012 so I will suggest following solution. I am using SQL Server 2012′s CHOOSE function. It is SELECT GETDATE() Today, DATENAME(dw, GETDATE()) DayofWeek, CHOOSE(DATEPART(dw, GETDATE()), 'WEEKEND','Weekday', 'Weekday','Weekday','Weekday','Weekday','WEEKEND') WorkDay GO You can use the choose function on table as well. Here is the quick example of the same. USE AdventureWorks2012 GO SELECT A.ModifiedDate, DATENAME(dw, A.ModifiedDate) DayofWeek, CHOOSE(DATEPART(dw, A.ModifiedDate), 'WEEKEND','Weekday', 'Weekday','Weekday','Weekday','Weekday','WEEKEND') WorkDay FROM [Person].[Address] A GO If you are using an earlier version of the SQL Server you can use a CASE statement instead of CHOOSE function. Please read my earlier article which discusses CHOOSE function and CASE statements. Logical Function – CHOOSE() – A Quick Introduction Reference:  Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Fix overlapping partitions

  - by Alex

  I have problem with overlapping partitions. GParted shows me all my disk as unallocated area, output of fdisk below: alex@alex-ThinkPad-SL510:~$ sudo fdisk -l /dev/sda Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xfb4b9b90 Device Boot Start End Blocks Id System /dev/sda1 * 2048 2457599 1227776 7 HPFS/NTFS/exFAT /dev/sda2 2457600 571351724 284447062+ 7 HPFS/NTFS/exFAT /dev/sda3 571342846 604661759 16659457 5 Extended /dev/sda4 604661760 625137663 10237952 7 HPFS/NTFS/exFAT /dev/sda5 598650880 604661759 3005440 82 Linux swap / Solaris /dev/sda6 571342848 598650879 13654016 83 Linux Partition table entries are not in disk order Do I understand correctly that overlapping partitions are sda2 and sda3 (sda2 and sda6 overlaps too, because sda6 is the first chunk of sda3, sda3 has type "extended")? Are sda2 and sda3 the cause of problem? How can i fix it without deleting partitions? My OS is Ubuntu 12.04, 64 bit. Thanks in advance.

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• Cannot mount Android phone in Ubuntu and sync with Banshee

  - by Brett Alton

  I can't get my LG Optimus One to sync with Banshee. I read somewhere that the root needs to have an empty file called '.is_audio_player'. I did that and it still doesn't mount. I ran dmesg however and it appears that the card is unmounting before I even have a change to run Banshee. [ 7250.321359] usb 1-1.4: new high speed USB device using ehci_hcd and address 10 [ 7250.444795] scsi12 : usb-storage 1-1.4:1.0 [ 7251.567946] scsi 12:0:0:0: Direct-Access Multiple Card Reader 1.00 PQ: 0 ANSI: 0 [ 7251.568839] sd 12:0:0:0: Attached scsi generic sg3 type 0 [ 7252.232433] sd 12:0:0:0: [sdc] 15564800 512-byte logical blocks: (7.96 GB/7.42 GiB) [ 7252.233299] sd 12:0:0:0: [sdc] Write Protect is off [ 7252.233306] sd 12:0:0:0: [sdc] Mode Sense: 03 00 00 00 [ 7252.233309] sd 12:0:0:0: [sdc] Assuming drive cache: write through [ 7252.235658] sd 12:0:0:0: [sdc] Assuming drive cache: write through [ 7252.235666] sdc: sdc1 [ 7252.239132] sd 12:0:0:0: [sdc] Assuming drive cache: write through [ 7252.239140] sd 12:0:0:0: [sdc] Attached SCSI removable disk [ 7272.573437] usb 1-1.4: USB disconnect, address 10 Suggestions?

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• Why lock-free data structures just aren't lock-free enough

  - by Alex.Davies

  Today's post will explore why the current ways to communicate between threads don't scale, and show you a possible way to build scalable parallel programming on top of shared memory. The problem with shared memory Soon, we will have dozens, hundreds and then millions of cores in our computers. It's inevitable, because individual cores just can't get much faster. At some point, that's going to mean that we have to rethink our architecture entirely, as millions of cores can't all access a shared memory space efficiently. But millions of cores are still a long way off, and in the meantime we'll see machines with dozens of cores, struggling with shared memory. Alex's tip: The best way for an application to make use of that increasing parallel power is to use a concurrency model like actors, that deals with synchronisation issues for you. Then, the maintainer of the actors framework can find the most efficient way to coordinate access to shared memory to allow your actors to pass messages to each other efficiently. At the moment, NAct uses the .NET thread pool and a few locks to marshal messages. It works well on dual and quad core machines, but it won't scale to more cores. Every time we use a lock, our core performs an atomic memory operation (eg. CAS) on a cell of memory representing the lock, so it's sure that no other core can possibly have that lock. This is very fast when the lock isn't contended, but we need to notify all the other cores, in case they held the cell of memory in a cache. As the number of cores increases, the total cost of a lock increases linearly. A lot of work has been done on "lock-free" data structures, which avoid locks by using atomic memory operations directly. These give fairly dramatic performance improvements, particularly on systems with a few (2 to 4) cores. The .NET 4 concurrent collections in System.Collections.Concurrent are mostly lock-free. However, lock-free data structures still don't scale indefinitely, because any use of an atomic memory operation still involves every core in the system. A sync-free data structure Some concurrent data structures are possible to write in a completely synchronization-free way, without using any atomic memory operations. One useful example is a single producer, single consumer (SPSC) queue. It's easy to write a sync-free fixed size SPSC queue using a circular buffer*. Slightly trickier is a queue that grows as needed. You can use a linked list to represent the queue, but if you leave the nodes to be garbage collected once you're done with them, the GC will need to involve all the cores in collecting the finished nodes. Instead, I've implemented a proof of concept inspired by this intel article which reuses the nodes by putting them in a second queue to send back to the producer. * In all these cases, you need to use memory barriers correctly, but these are local to a core, so don't have the same scalability problems as atomic memory operations. Performance tests I tried benchmarking my SPSC queue against the .NET ConcurrentQueue, and against a standard Queue protected by locks. In some ways, this isn't a fair comparison, because both of these support multiple producers and multiple consumers, but I'll come to that later. I started on my dual-core laptop, running a simple test that had one thread producing 64 bit integers, and another consuming them, to measure the pure overhead of the queue. So, nothing very interesting here. Both concurrent collections perform better than the lock-based one as expected, but there's not a lot to choose between the ConcurrentQueue and my SPSC queue. I was a little disappointed, but then, the .NET Framework team spent a lot longer optimising it than I did. So I dug out a more powerful machine that Red Gate's DBA tools team had been using for testing. It is a 6 core Intel i7 machine with hyperthreading, adding up to 12 logical cores. Now the results get more interesting. As I increased the number of producer-consumer pairs to 6 (to saturate all 12 logical cores), the locking approach was slow, and got even slower, as you'd expect. What I didn't expect to be so clear was the drop-off in performance of the lock-free ConcurrentQueue. I could see the machine only using about 20% of available CPU cycles when it should have been saturated. My interpretation is that as all the cores used atomic memory operations to safely access the queue, they ended up spending most of the time notifying each other about cache lines that need invalidating. The sync-free approach scaled perfectly, despite still working via shared memory, which after all, should still be a bottleneck. I can't quite believe that the results are so clear, so if you can think of any other effects that might cause them, please comment! Obviously, this benchmark isn't realistic because we're only measuring the overhead of the queue. Any real workload, even on a machine with 12 cores, would dwarf the overhead, and there'd be no point worrying about this effect. But would that be true on a machine with 100 cores? Still to be solved. The trouble is, you can't build many concurrent algorithms using only an SPSC queue to communicate. In particular, I can't see a way to build something as general purpose as actors on top of just SPSC queues. Fundamentally, an actor needs to be able to receive messages from multiple other actors, which seems to need an MPSC queue. I've been thinking about ways to build a sync-free MPSC queue out of multiple SPSC queues and some kind of sign-up mechanism. Hopefully I'll have something to tell you about soon, but leave a comment if you have any ideas.

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• Where can I find the application executables in the filesystem?

  - by richzilla

  Where are executables for programs stored in Ubuntu? An application (Komodo Edit) is asking me to identify an application to be used as a web browser. I've become used to just entering the application name as a command for situations such as these, but this scenario got me thinking. I know in Windows it would just be the relevant application folder in the 'program files' folder, but I'm assuming things are a bit different on Linux? I thought somewhere like bin would be logical but this appears to standard Linux/Unix applications. Where would I find the binary executable for applications stored on my system?

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• ubuntu 12.04 does not detect already installed windows 7

  - by arvind

  sir i have alreary installed windows 7 ultimate and when i tried to install ubuntu 12.04 it's installer didn't detect windows even i have only two primary and two logical partition on windows when i goes through try ubuntu and use command " os-prober" it shows output like as " unshare failed: Operation not permitted ERROR: you must be root ERROR: you must be root ERROR: you must be root ERROR: you must be root ERROR: you must be root ERROR: you must be root mkdir: cannot create directory /var/lib/os-prober/mount': Permission denied mkdir: cannot create directory/var/lib/os-prober/mount': Permission denied mkdir: cannot create directory /var/lib/os-prober/mount': Permission denied mkdir: cannot create directory/var/lib/os-prober/mount': Permission denied mkdir: cannot create directory `/var/lib/os-prober/mount': Permission denied" so plzzzz help me what should i do ???

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• PTLQueue : a scalable bounded-capacity MPMC queue

  - by Dave

  Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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• QotD: Roger Yeung on Oracle's Java Uninstall Applet

  - by $utils.escapeXML($entry.author)

  We have a build of an Applet that will assist in the removal of older versions of the JRE. The Applet is available for testing on http://java.com/uninstall-tool . At this stage the Applet only targets the Windows platform, as it represents the largest installed base and the need for platform specific elements made Windows the logical starting point. We are deliberately not giving documentation on how to use the applet - we want feedback of the tool standing on its own.The intent of making this build available is to gather feedback; ideas, suggestions, comments, good and bad, what works, what does not work, what could be improved, etc. Please try it out and give us feedback to ensure a smooth release.Roger Yeung in a post with more details on providing feedback.

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• GParted doesn't see any partition

  - by Diego

  What I am trying to do couldn't be more logical I think. I have a 40gb drive with two partitions, Xp and Ubuntu. I have dual boot, everything boots and works perfectly. I have about 9gb free in the Windows partition When I run Gparted I only see 40gb unallocated space, booting from Gparted Live CD. What the hell is going on ? I've read everywhere this is a common problem, however it has no sense something like this remains unsolved by gparted developers, considering what I am trying to do is the very basic step anybody wanting to migrate from Windows to Linux would od Something like this honestly doesn't give anything else than frustration Could anybody on this forum be so kind to explain whats' going on ? Thanks

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• Being prepared for a code review as a developer?

  - by Karthik Sreenivasan

  I am looking for some ideas here. I read the article How should code reviews be Carried Out and Code Reviews, what are the advantages? which were very informative but I still need more clarity on the question below. My Question is, Being the target developer, can you suggest some best practices a developer can incorporate before his code is going get reviewed. Currently I practice the following methods PPT for a logical flow Detailed comments. Issue: Even though I have implemented the above practices, they do not help on the review. The problem I faced is, when certain logic is referred, I keep searching for the implementation and the flow and too much time is wasted in the process and I get on people’s nerve. I think a lot of developers would be going through what I am going through as well.

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• Installed Ubuntu 14.04LTS

  - by user291729

  On my laptop which came pre-installed with Windows 8.1. Felt I needed to see the competition for myself to establish which was a better OS. So I followed the channels to dual boot. All seemed fine and I accessed Ubuntu with no issues after selecting this from the menu to select the OS. I should add that the boot method was changed to legacy. However, since using Ubuntu, I no longer have the ability to select the OS. The laptop simply logs straight into Ubuntu. I therefore attempted to access the recovery options, only it appears the Windows 8 bootloader has somehow been corrupted as I am now told to use the Windows 8 recovery disc (which, as this was pre-installed - I do not have). Left with no other alternative, I have scoured these forums without success, and so I am hoping someone in the know (or who has experienced similar) can help. I have tried boot repair again without success. On rebooting I am only presented with a basic splash screen asking me to select Ubuntu, Memtest, Windows 8 Recovery or Windows 8 Bootloader (The bootloaders again require I insert the disc). I have tried Code: cat /boot/grub/grub.cfg df -h sudo fdisk -l cat /proc/partitions # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi if [ "${next_entry}" ] ; then set default="${next_entry}" set next_entry= save_env next_entry set boot_once=true else set default="0" fi if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=800x600 load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_GB insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ] ; then set timeout=-1 else if [ x$feature_timeout_style = xy ] ; then set timeout_style=menu set timeout=20 # Fallback normal timeout code in case the timeout_style feature is # unavailable. else set timeout=20 fi fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { menuentry 'Ubuntu, with Linux 3.13.0-29-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-29-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-recovery-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro recovery nomodeset vga=789 quiet echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-recovery-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro recovery nomodeset vga=789 quiet echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry 'Memory test (memtest86+)' { insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi knetbsd /boot/memtest86+.elf } menuentry 'Memory test (memtest86+, serial console 115200)' { insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry 'Windows Recovery Environment (loader) (on /dev/sda2)' --class windows --class os $menuentry_id_option 'osprober-chain-7A6A69D66A698FA5' { insmod part_gpt insmod ntfs set root='hd0,gpt2' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2 7A6A69D66A698FA5 else search --no-floppy --fs-uuid --set=root 7A6A69D66A698FA5 fi drivemap -s (hd0) ${root} chainloader +1 } menuentry 'Windows 8 (loader) (on /dev/sda3)' --class windows --class os $menuentry_id_option 'osprober-chain-8C88-80F7' { insmod part_gpt insmod fat set root='hd0,gpt3' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt3 --hint-efi=hd0,gpt3 --hint-baremetal=ahci0,gpt3 8C88-80F7 else search --no-floppy --fs-uuid --set=root 8C88-80F7 fi drivemap -s (hd0) ${root} chainloader +1 } set timeout_style=menu if [ "${timeout}" = 0 ]; then set timeout=10 fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi if [ "${next_entry}" ] ; then set default="${next_entry}" set next_entry= save_env next_entry set boot_once=true else set default="0" fi if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=800x600 load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_GB insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ] ; then set timeout=-1 else if [ x$feature_timeout_style = xy ] ; then set timeout_style=menu set timeout=20 # Fallback normal timeout code in case the timeout_style feature is # unavailable. else set timeout=20 fi fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { menuentry 'Ubuntu, with Linux 3.13.0-29-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-29-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-recovery-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro recovery nomodeset vga=789 quiet echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-advanced-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro vga=789 quiet quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-recovery-d2f10f36-e3bb-4d83-a9b8-5d456fc454ad' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic root=UUID=d2f10f36-e3bb-4d83-a9b8-5d456fc454ad ro recovery nomodeset vga=789 quiet echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry 'Memory test (memtest86+)' { insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi knetbsd /boot/memtest86+.elf } menuentry 'Memory test (memtest86+, serial console 115200)' { insmod part_gpt insmod ext2 set root='hd0,gpt9' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt9 --hint-efi=hd0,gpt9 --hint-baremetal=ahci0,gpt9 d2f10f36-e3bb-4d83-a9b8-5d456fc454ad else search --no-floppy --fs-uuid --set=root d2f10f36-e3bb-4d83-a9b8-5d456fc454ad fi linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry 'Windows Recovery Environment (loader) (on /dev/sda2)' --class windows --class os $menuentry_id_option 'osprober-chain-7A6A69D66A698FA5' { insmod part_gpt insmod ntfs set root='hd0,gpt2' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2 7A6A69D66A698FA5 else search --no-floppy --fs-uuid --set=root 7A6A69D66A698FA5 fi drivemap -s (hd0) ${root} chainloader +1 } menuentry 'Windows 8 (loader) (on /dev/sda3)' --class windows --class os $menuentry_id_option 'osprober-chain-8C88-80F7' { insmod part_gpt insmod fat set root='hd0,gpt3' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt3 --hint-efi=hd0,gpt3 --hint-baremetal=ahci0,gpt3 8C88-80F7 else search --no-floppy --fs-uuid --set=root 8C88-80F7 fi drivemap -s (hd0) ${root} chainloader +1 } set timeout_style=menu if [ "${timeout}" = 0 ]; then set timeout=10 fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### john@john-SVE1713Y1EB:~$ ^C john@john-SVE1713Y1EB:~$ ^C john@john-SVE1713Y1EB:~$ df -h Filesystem Size Used Avail Use% Mounted on /dev/sda9 84G 7.1G 73G 9% / none 4.0K 0 4.0K 0% /sys/fs/cgroup udev 3.9G 4.0K 3.9G 1% /dev tmpfs 794M 1.4M 793M 1% /run none 5.0M 0 5.0M 0% /run/lock none 3.9G 80K 3.9G 1% /run/shm none 100M 52K 100M 1% /run/user /dev/sdc1 7.5G 2.2G 5.4G 29% /media/john/DYLANMUSIC /dev/sr0 964M 964M 0 100% /media/john/Ubuntu 14.04 LTS amd64 /dev/sdb1 1.9T 892G 972G 48% /media/john/Storage Main WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x4e2ccf75 Device Boot Start End Blocks Id System /dev/sda1 1 1953525167 976762583+ ee GPT Partition 1 does not start on physical sector boundary. Disk /dev/sdc: 8011 MB, 8011120640 bytes 41 heads, 41 sectors/track, 9307 cylinders, total 15646720 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc3072e18 Device Boot Start End Blocks Id System /dev/sdc1 8064 15646719 7819328 b W95 FAT32 Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc7d968ff Device Boot Start End Blocks Id System /dev/sdb1 64 3907029119 1953514528 7 HPFS/NTFS/exFAT major minor #blocks name 8 0 976762584 sda 8 1 266240 sda1 8 2 1509376 sda2 8 3 266240 sda3 8 4 131072 sda4 8 5 841012780 sda5 8 6 358400 sda6 8 7 35376128 sda7 8 8 1024 sda8 8 9 89501696 sda9 8 10 8337408 sda10 11 0 987136 sr0 8 32 7823360 sdc 8 33 7819328 sdc1 8 16 1953514584 sdb 8 17 1953514528 sdb1 I am no expert on this and I'm at a loss as how to correct this without having to re-format everything and reinstall Windows 8. However, if I'm to try using Ubuntu again then there is the risk this problem may come back. Again, I did not do anything manually - the installer did everything (with the exception of changing the boot to Legacy to allow the booting of another bootloader). LiveCD works but doesn't give me the options that I've seen here and as mentioned earlier, only boot recovery only gives me the options as mentioned earlier. Also this fails to load via USB (possibly because HDD comes before USB in the boot order?). Being used to a Windows environment, the Ubuntu (and Linux) environment is a dive at a less than comfortable depth at present (but one I fully intend to get to grips with - especially the commands being more common via Terminal). I very much appreciate the help with this guys.

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• How can I continue playing music after hibernating my laptop?

  - by Olivier

  I have a laptop with ubuntu 12.04, I want to be able to play music with it while it is on hybernate mode, the problem is: when I close my laptop it goes to hybernate (I know this is a default and I know where to change this, but I can't change whether the system is playing music during hybernate or not) while I'm playing music, it stops the music as well (this sounds logical because hybernate mode is for saving power, but I'd like my computer to continue playing music). Is there a possibility of changing this? If not, can there be an update or something which creates a tiny option in the hybernate or the sound menu for this?

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• Builder Pattern: When to fail?

  - by skiwi

  When implementing the Builder Pattern, I often find myself confused with when to let building fail and I even manage to take different stands on the matter every few days. First some explanation: With failing early I mean that building an object should fail as soon as an invalid parameter is passed in. So inside the SomeObjectBuilder. With failing late I mean that building an object only can fail on the build() call that implicitely calls a constructor of the object to be built. Then some arguments: In favor of failing late: A builder class should be no more than a class that simply holds values. Moreover, it leads to less code duplication. In favor of failing early: A general approach in software programming is that you want to detect issues as early as possible and therefore the most logical place to check would be in the builder class' constructor, 'setters' and ultimately in the build method. What is the general concensus about this?

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• Robots.txt never downloaded but some blocked URLs in GWT

  - by Zistoloen

  There is something I don't understand in Google Webmaster Tools (GWT) for my Wordpress site. In menu "Blocked URLs", it mention that my robots.txt has never been downloaded but there are some blocked URLs. It's kind of weird and not logical. Am i missing something? User-agent : * Disallow: /*? Disallow: /wp-login.php Disallow: /wp-admin Disallow: /wp-includes Disallow: /wp-content Allow: /wp-content/uploads Disallow: */trackback Disallow: /*/feed Disallow: /*/comments Disallow: /cgi-bin Disallow: /*.php$ Disallow: /*.inc$ Disallow: /*.gz$ Disallow: /*.cgi$ Disallow: /author/* I'm afraid my robots.txt doesn't block several URLs I want to block.

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• Web and Flex developer career question [closed]

  - by abhilashm86

  Possible Duplicate: should i concentrate on logical and puzzles part in programming, i want to be a web (flex)developer? I'm a computer science student and have been learning Flex and Actionscript 3.0 for 4 months. I know it's easy to program in MXML, and Actionscript 3.0 is pretty easy with bunch of classes, but when I try to code in C++ or C, I struggle, I feel I'm being inefficient and it scares me. Since I'm a student, I've no experience in developing algorithms and tough program solving? I'd like to be a web developer. Does a web developer need strong fundamentals when it comes to things such as complex algorithms and high end coding?

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• Unable to install on a Samsung 305v5a

  - by Antony

  Have used Ubuntu for years now. Bought a Samsung 305v5a-so2 laptop yesterday. It runs an AMD A8 quadcore. I have a CD of 10.04 and as I am not clear about whether to install 32 or 64 bit I thought I would run the trial of ubuntu from the cd to see it. After about 30m started getting Authentification Failure messages. Squashfs-error Unable to read fragment cash entry Then a zillion Buffer Logical error messages like 17,000+ Should I go download 11.10, in 32bit or go and try the 64bit. Really don't want to screw the new laptop already but aint gonna wanna work with w7 either. Thanks for any help

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• Informed TDD &ndash; Kata &ldquo;To Roman Numerals&rdquo;

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/05/28/informed-tdd-ndash-kata-ldquoto-roman-numeralsrdquo.aspxIn a comment on my article on what I call Informed TDD (ITDD) reader gustav asked how this approach would apply to the kata “To Roman Numerals”. And whether ITDD wasn´t a violation of TDD´s principle of leaving out “advanced topics like mocks”. I like to respond with this article to his questions. There´s more to say than fits into a commentary. Mocks and TDD I don´t see in how far TDD is avoiding or opposed to mocks. TDD and mocks are orthogonal. TDD is about pocess, mocks are about structure and costs. Maybe by moving forward in tiny red+green+refactor steps less need arises for mocks. But then… if the functionality you need to implement requires “expensive” resource access you can´t avoid using mocks. Because you don´t want to constantly run all your tests against the real resource. True, in ITDD mocks seem to be in almost inflationary use. That´s not what you usually see in TDD demonstrations. However, there´s a reason for that as I tried to explain. I don´t use mocks as proxies for “expensive” resource. Rather they are stand-ins for functionality not yet implemented. They allow me to get a test green on a high level of abstraction. That way I can move forward in a top-down fashion. But if you think of mocks as “advanced” or if you don´t want to use a tool like JustMock, then you don´t need to use mocks. You just need to stand the sight of red tests for a little longer ;-) Let me show you what I mean by that by doing a kata. ITDD for “To Roman Numerals” gustav asked for the kata “To Roman Numerals”. I won´t explain the requirements again. You can find descriptions and TDD demonstrations all over the internet, like this one from Corey Haines. Now here is, how I would do this kata differently. 1. Analyse A demonstration of TDD should never skip the analysis phase. It should be made explicit. The requirements should be formalized and acceptance test cases should be compiled. “Formalization” in this case to me means describing the API of the required functionality. “[D]esign a program to work with Roman numerals” like written in this “requirement document” is not enough to start software development. Coding should only begin, if the interface between the “system under development” and its context is clear. If this interface is not readily recognizable from the requirements, it has to be developed first. Exploration of interface alternatives might be in order. It might be necessary to show several interface mock-ups to the customer – even if that´s you fellow developer. Designing the interface is a task of it´s own. It should not be mixed with implementing the required functionality behind the interface. Unfortunately, though, this happens quite often in TDD demonstrations. TDD is used to explore the API and implement it at the same time. To me that´s a violation of the Single Responsibility Principle (SRP) which not only should hold for software functional units but also for tasks or activities. In the case of this kata the API fortunately is obvious. Just one function is needed: string ToRoman(int arabic). And it lives in a class ArabicRomanConversions. Now what about acceptance test cases? There are hardly any stated in the kata descriptions. Roman numerals are explained, but no specific test cases from the point of view of a customer. So I just “invent” some acceptance test cases by picking roman numerals from a wikipedia article. They are supposed to be just “typical examples” without special meaning. Given the acceptance test cases I then try to develop an understanding of the problem domain. I´ll spare you that. The domain is trivial and is explain in almost all kata descriptions. How roman numerals are built is not difficult to understand. What´s more difficult, though, might be to find an efficient solution to convert into them automatically. 2. Solve The usual TDD demonstration skips a solution finding phase. Like the interface exploration it´s mixed in with the implementation. But I don´t think this is how it should be done. I even think this is not how it really works for the people demonstrating TDD. They´re simplifying their true software development process because they want to show a streamlined TDD process. I doubt this is helping anybody. Before you code you better have a plan what to code. This does not mean you have to do “Big Design Up-Front”. It just means: Have a clear picture of the logical solution in your head before you start to build a physical solution (code). Evidently such a solution can only be as good as your understanding of the problem. If that´s limited your solution will be limited, too. Fortunately, in the case of this kata your understanding does not need to be limited. Thus the logical solution does not need to be limited or preliminary or tentative. That does not mean you need to know every line of code in advance. It just means you know the rough structure of your implementation beforehand. Because it should mirror the process described by the logical or conceptual solution. Here´s my solution approach: The arabic “encoding” of numbers represents them as an ordered set of powers of 10. Each digit is a factor to multiply a power of ten with. The “encoding” 123 is the short form for a set like this: {1*10^2, 2*10^1, 3*10^0}. And the number is the sum of the set members. The roman “encoding” is different. There is no base (like 10 for arabic numbers), there are just digits of different value, and they have to be written in descending order. The “encoding” XVI is short for [10, 5, 1]. And the number is still the sum of the members of this list. The roman “encoding” thus is simpler than the arabic. Each “digit” can be taken at face value. No multiplication with a base required. But what about IV which looks like a contradiction to the above rule? It is not – if you accept roman “digits” not to be limited to be single characters only. Usually I, V, X, L, C, D, M are viewed as “digits”, and IV, IX etc. are viewed as nuisances preventing a simple solution. All looks different, though, once IV, IX etc. are taken as “digits”. Then MCMLIV is just a sum: M+CM+L+IV which is 1000+900+50+4. Whereas before it would have been understood as M-C+M+L-I+V – which is more difficult because here some “digits” get subtracted. Here´s the list of roman “digits” with their values: {1, I}, {4, IV}, {5, V}, {9, IX}, {10, X}, {40, XL}, {50, L}, {90, XC}, {100, C}, {400, CD}, {500, D}, {900, CM}, {1000, M} Since I take IV, IX etc. as “digits” translating an arabic number becomes trivial. I just need to find the values of the roman “digits” making up the number, e.g. 1954 is made up of 1000, 900, 50, and 4. I call those “digits” factors. If I move from the highest factor (M=1000) to the lowest (I=1) then translation is a two phase process: Find all the factors Translate the factors found Compile the roman representation Translation is just a look-up. Finding, though, needs some calculation: Find the highest remaining factor fitting in the value Remember and subtract it from the value Repeat with remaining value and remaining factors Please note: This is just an algorithm. It´s not code, even though it might be close. Being so close to code in my solution approach is due to the triviality of the problem. In more realistic examples the conceptual solution would be on a higher level of abstraction. With this solution in hand I finally can do what TDD advocates: find and prioritize test cases. As I can see from the small process description above, there are two aspects to test: Test the translation Test the compilation Test finding the factors Testing the translation primarily means to check if the map of factors and digits is comprehensive. That´s simple, even though it might be tedious. Testing the compilation is trivial. Testing factor finding, though, is a tad more complicated. I can think of several steps: First check, if an arabic number equal to a factor is processed correctly (e.g. 1000=M). Then check if an arabic number consisting of two consecutive factors (e.g. 1900=[M,CM]) is processed correctly. Then check, if a number consisting of the same factor twice is processed correctly (e.g. 2000=[M,M]). Finally check, if an arabic number consisting of non-consecutive factors (e.g. 1400=[M,CD]) is processed correctly. I feel I can start an implementation now. If something becomes more complicated than expected I can slow down and repeat this process. 3. Implement First I write a test for the acceptance test cases. It´s red because there´s no implementation even of the API. That´s in conformance with “TDD lore”, I´d say: Next I implement the API: The acceptance test now is formally correct, but still red of course. This will not change even now that I zoom in. Because my goal is not to most quickly satisfy these tests, but to implement my solution in a stepwise manner. That I do by “faking” it: I just “assume” three functions to represent the transformation process of my solution: My hypothesis is that those three functions in conjunction produce correct results on the API-level. I just have to implement them correctly. That´s what I´m trying now – one by one. I start with a simple “detail function”: Translate(). And I start with all the test cases in the obvious equivalence partition: As you can see I dare to test a private method. Yes. That´s a white box test. But as you´ll see it won´t make my tests brittle. It serves a purpose right here and now: it lets me focus on getting one aspect of my solution right. Here´s the implementation to satisfy the test: It´s as simple as possible. Right how TDD wants me to do it: KISS. Now for the second equivalence partition: translating multiple factors. (It´a pattern: if you need to do something repeatedly separate the tests for doing it once and doing it multiple times.) In this partition I just need a single test case, I guess. Stepping up from a single translation to multiple translations is no rocket science: Usually I would have implemented the final code right away. Splitting it in two steps is just for “educational purposes” here. How small your implementation steps are is a matter of your programming competency. Some “see” the final code right away before their mental eye – others need to work their way towards it. Having two tests I find more important. Now for the next low hanging fruit: compilation. It´s even simpler than translation. A single test is enough, I guess. And normally I would not even have bothered to write that one, because the implementation is so simple. I don´t need to test .NET framework functionality. But again: if it serves the educational purpose… Finally the most complicated part of the solution: finding the factors. There are several equivalence partitions. But still I decide to write just a single test, since the structure of the test data is the same for all partitions: Again, I´m faking the implementation first: I focus on just the first test case. No looping yet. Faking lets me stay on a high level of abstraction. I can write down the implementation of the solution without bothering myself with details of how to actually accomplish the feat. That´s left for a drill down with a test of the fake function: There are two main equivalence partitions, I guess: either the first factor is appropriate or some next. The implementation seems easy. Both test cases are green. (Of course this only works on the premise that there´s always a matching factor. Which is the case since the smallest factor is 1.) And the first of the equivalence partitions on the higher level also is satisfied: Great, I can move on. Now for more than a single factor: Interestingly not just one test becomes green now, but all of them. Great! You might say, then I must have done not the simplest thing possible. And I would reply: I don´t care. I did the most obvious thing. But I also find this loop very simple. Even simpler than a recursion of which I had thought briefly during the problem solving phase. And by the way: Also the acceptance tests went green: Mission accomplished. At least functionality wise. Now I´ve to tidy up things a bit. TDD calls for refactoring. Not uch refactoring is needed, because I wrote the code in top-down fashion. I faked it until I made it. I endured red tests on higher levels while lower levels weren´t perfected yet. But this way I saved myself from refactoring tediousness. At the end, though, some refactoring is required. But maybe in a different way than you would expect. That´s why I rather call it “cleanup”. First I remove duplication. There are two places where factors are defined: in Translate() and in Find_factors(). So I factor the map out into a class constant. Which leads to a small conversion in Find_factors(): And now for the big cleanup: I remove all tests of private methods. They are scaffolding tests to me. They only have temporary value. They are brittle. Only acceptance tests need to remain. However, I carry over the single “digit” tests from Translate() to the acceptance test. I find them valuable to keep, since the other acceptance tests only exercise a subset of all roman “digits”. This then is my final test class: And this is the final production code: Test coverage as reported by NCrunch is 100%: Reflexion Is this the smallest possible code base for this kata? Sure not. You´ll find more concise solutions on the internet. But LOC are of relatively little concern – as long as I can understand the code quickly. So called “elegant” code, however, often is not easy to understand. The same goes for KISS code – especially if left unrefactored, as it is often the case. That´s why I progressed from requirements to final code the way I did. I first understood and solved the problem on a conceptual level. Then I implemented it top down according to my design. I also could have implemented it bottom-up, since I knew some bottom of the solution. That´s the leaves of the functional decomposition tree. Where things became fuzzy, since the design did not cover any more details as with Find_factors(), I repeated the process in the small, so to speak: fake some top level, endure red high level tests, while first solving a simpler problem. Using scaffolding tests (to be thrown away at the end) brought two advantages: Encapsulation of the implementation details was not compromised. Naturally private methods could stay private. I did not need to make them internal or public just to be able to test them. I was able to write focused tests for small aspects of the solution. No need to test everything through the solution root, the API. The bottom line thus for me is: Informed TDD produces cleaner code in a systematic way. It conforms to core principles of programming: Single Responsibility Principle and/or Separation of Concerns. Distinct roles in development – being a researcher, being an engineer, being a craftsman – are represented as different phases. First find what, what there is. Then devise a solution. Then code the solution, manifest the solution in code. Writing tests first is a good practice. But it should not be taken dogmatic. And above all it should not be overloaded with purposes. And finally: moving from top to bottom through a design produces refactored code right away. Clean code thus almost is inevitable – and not left to a refactoring step at the end which is skipped often for different reasons.   PS: Yes, I have done this kata several times. But that has only an impact on the time needed for phases 1 and 2. I won´t skip them because of that. And there are no shortcuts during implementation because of that.

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• How do I overcome paralysis by analysis when coding?

  - by LuxuryMode

  When I start a new project, I often times immediately start thinking about the details of implementation. "Where am I gonna put the DataBaseHandler? How should I use it? Should classes that want to use it extend from some Abstract superclass..? Should I an interface? What level of abstraction am I going to use in my class that contains methods for sending requests and parsing data?" I end up stalling for a long time because I want to code for extensibility and reusability. But I feel it almost impossible to get past thinking about how to implement perfectly. And then, if I try to just say "screw it, just get it done!", I hit a brick wall pretty quickly because my code isn't organized, I mixed levels of abstractions, etc. What are some techniques/methods you have for launching into a new project while also setting up a logical/modular structure that will scale well?

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• Cannot connect to secure wireless with Netgear wna3100 USB

  - by Vince Radice

  I have installed Ubuntu 11.10. I used a wired connection to download and install all of the updates. When I tried to use a Netgear WNA3100 wireless USB network adapter, it failed. Much searching and trying things I was finally able to get it working by disabling security on my router. I have verified this by disabling security and I was able to connect. When I enabled security (WPA2 PSK), the connection failed. What is necessary to enable security (WPA2 PSK) and still use the Netgear USB interface? Here is the output from the commands most requested lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 003: ID 0846:9020 NetGear, Inc. WNA3100(v1) Wireless-N 300 [Broadcom BCM43231] lshw -C network *-network description: Ethernet interface product: RTL-8139/8139C/8139C+ vendor: Realtek Semiconductor Co., Ltd. physical id: 3 bus info: pci@0000:02:03.0 logical name: eth0 version: 10 serial: 00:40:ca:44:e6:3e size: 10Mbit/s capacity: 100Mbit/s width: 32 bits clock: 33MHz capabilities: pm bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=8139too driverversion=0.9.28 duplex=half latency=32 link=no maxlatency=64 mingnt=32 multicast=yes port=MII speed=10Mbit/s resources: irq:19 ioport:c800(size=256) memory:ee011000-ee0110ff memory:40000000-4000ffff *-network description: Wireless interface physical id: 1 logical name: wlan0 serial: e0:91:f5:56:e1:0d capabilities: ethernet physical wireless configuration: broadcast=yes driver=ndiswrapper+bcmn43xx32 driverversion=1.56+,08/26/2009, 5.10.79.30 ip=192.168.1.104 link=yes multicast=yes wireless=IEEE 802.11g iwconfig lo no wireless extensions. eth0 no wireless extensions. wlan0 IEEE 802.11g ESSID:"vincecarolradice" Mode:Managed Frequency:2.422 GHz Access Point: A0:21:B7:9F:E5:EE Bit Rate=121.5 Mb/s Tx-Power:32 dBm RTS thr:2347 B Fragment thr:2346 B Encryption key:off Power Management:off Link Quality:76/100 Signal level:-47 dBm Noise level:-96 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 ndiswrapper -l bcmn43xx32 : driver installed device (0846:9020) present lsmod | grep ndis ndiswrapper 193669 0 dmesg | grep -e ndis -e wlan [ 907.466392] ndiswrapper version 1.56 loaded (smp=yes, preempt=no) [ 907.838507] ndiswrapper (import:233): unknown symbol: ntoskrnl.exe:'IoUnregisterPlugPlayNotification' [ 907.838955] ndiswrapper: driver bcmwlhigh5 (Netgear,11/05/2009, 5.60.180.11) loaded [ 908.137940] wlan0: ethernet device e0:91:f5:56:e1:0d using NDIS driver: bcmwlhigh5, version: 0x53cb40b, NDIS version: 0x501, vendor: 'NDIS Network Adapter', 0846:9020.F.conf [ 908.141879] wlan0: encryption modes supported: WEP; TKIP with WPA, WPA2, WPA2PSK; AES/CCMP with WPA, WPA2, WPA2PSK [ 908.143048] usbcore: registered new interface driver ndiswrapper [ 908.178826] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 994.015088] usbcore: deregistering interface driver ndiswrapper [ 994.028892] ndiswrapper: device wlan0 removed [ 994.080558] ndiswrapper version 1.56 loaded (smp=yes, preempt=no) [ 994.374929] ndiswrapper: driver bcmn43xx32 (,08/26/2009, 5.10.79.30) loaded [ 994.404366] ndiswrapper (mp_init:219): couldn't initialize device: C0000001 [ 994.404384] ndiswrapper (pnp_start_device:435): Windows driver couldn't initialize the device (C0000001) [ 994.404666] ndiswrapper (mp_halt:262): device e05b6480 is not initialized - not halting [ 994.404671] ndiswrapper: device eth%d removed [ 994.404709] ndiswrapper: probe of 1-5:1.0 failed with error -22 [ 994.406318] usbcore: registered new interface driver ndiswrapper [ 2302.058692] wlan0: ethernet device e0:91:f5:56:e1:0d using NDIS driver: bcmn43xx32, version: 0x50a4f1e, NDIS version: 0x501, vendor: 'NDIS Network Adapter', 0846:9020.F.conf [ 2302.060882] wlan0: encryption modes supported: WEP; TKIP with WPA, WPA2, WPA2PSK; AES/CCMP with WPA, WPA2, WPA2PSK [ 2302.113838] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 2354.611318] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 2355.268902] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready [ 2365.400023] wlan0: no IPv6 routers present [ 2779.226096] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 2779.422343] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 2797.574474] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 2802.607937] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 2803.261315] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready [ 2813.952028] wlan0: no IPv6 routers present [ 3135.738431] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 3139.180963] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3139.816561] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3163.229872] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3163.444542] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3163.758297] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3163.860684] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3205.118732] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3205.139553] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3205.300542] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3353.341402] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 3363.266399] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3363.505475] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3363.506619] ndiswrapper (set_iw_auth_mode:601): setting auth mode to 5 failed (00010003) [ 3363.717203] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3363.779206] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3405.206152] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3405.248624] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3405.577664] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3438.852457] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 3438.908573] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3568.282995] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3568.325237] ndiswrapper (set_iw_auth_mode:601): setting auth mode to 5 failed (00010003) [ 3568.460716] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3568.461763] ndiswrapper (set_iw_auth_mode:601): setting auth mode to 5 failed (00010003) [ 3568.809776] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3568.880641] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3610.122848] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3610.148328] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3610.324502] ADDRCONF(NETDEV_UP): wlan0: link is not ready [ 3636.088798] ndiswrapper (iw_set_auth:1602): invalid cmd 12 [ 3636.712186] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready [ 3647.600040] wlan0: no IPv6 routers present I am using the system now with the router security turned off. When I submit this, I will turn security back on.

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• Wireless not working on Dell XPS 17 after installing 12.04

  - by user60622

  I (linux newbie) have a Dell XPS 17 and tried to install Ubuntu 12.04. After installation all WLAN accesspoints near are detected. But I can not connect (but I am able to connect with other computers as well as with Dell XPS 17 under windows). Outputs: iwconfig lo no wireless extensions. wlan0 IEEE 802.11bg ESSID:"LerchenPoint" Mode:Managed Frequency:2.412 GHz Access Point: 58:6D:8F:A0:2D:58 Bit Rate=1 Mb/s Tx-Power=14 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=70/70 Signal level=-37 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:19 Missed beacon:0 eth0 no wireless extensions. sudo lshw -class network *-network description: Wireless interface product: Centrino Wireless-N 1000 vendor: Intel Corporation physical id: 0 bus info: pci@0000:04:00.0 logical name: wlan0 version: 00 serial: 00:26:c7:99:98:28 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=iwlwifi driverversion=3.2.0-24-generic firmware=39.31.5.1 build 35138 latency=0 link=no multicast=yes wireless=IEEE 802.11bg resources: irq:50 memory:f0400000-f0401fff *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:0a:00.0 logical name: eth0 version: 06 serial: f0:4d:a2:56:e3:94 size: 1Gbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168e-2.fw ip=192.168.0.123 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s resources: irq:47 ioport:6000(size=256) memory:f0a04000-f0a04fff memory:f0a00000-f0a03fff dmesg | grep iwl [ 10.157531] iwlwifi 0000:04:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17 [ 10.157561] iwlwifi 0000:04:00.0: setting latency timer to 64 [ 10.157598] iwlwifi 0000:04:00.0: pci_resource_len = 0x00002000 [ 10.157599] iwlwifi 0000:04:00.0: pci_resource_base = ffffc90011090000 [ 10.157601] iwlwifi 0000:04:00.0: HW Revision ID = 0x0 [ 10.157731] iwlwifi 0000:04:00.0: irq 50 for MSI/MSI-X [ 10.157834] iwlwifi 0000:04:00.0: Detected Intel(R) Centrino(R) Wireless-N 1000 BGN, REV=0x6C [ 10.157976] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S [ 10.179772] iwlwifi 0000:04:00.0: device EEPROM VER=0x15d, CALIB=0x6 [ 10.179775] iwlwifi 0000:04:00.0: Device SKU: 0X50 [ 10.179777] iwlwifi 0000:04:00.0: Valid Tx ant: 0X1, Valid Rx ant: 0X3 [ 10.179796] iwlwifi 0000:04:00.0: Tunable channels: 13 802.11bg, 0 802.11a channels [ 10.574728] iwlwifi 0000:04:00.0: loaded firmware version 39.31.5.1 build 35138 [ 10.726409] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs' [ 19.714132] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S [ 19.777862] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S [ 2251.603089] iwlwifi 0000:04:00.0: PCI INT A disabled [ 2266.578350] iwlwifi 0000:04:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17 [ 2266.578399] iwlwifi 0000:04:00.0: setting latency timer to 64 [ 2266.578435] iwlwifi 0000:04:00.0: pci_resource_len = 0x00002000 [ 2266.578437] iwlwifi 0000:04:00.0: pci_resource_base = ffffc90011090000 [ 2266.578439] iwlwifi 0000:04:00.0: HW Revision ID = 0x0 [ 2266.578704] iwlwifi 0000:04:00.0: irq 50 for MSI/MSI-X [ 2266.578808] iwlwifi 0000:04:00.0: Detected Intel(R) Centrino(R) Wireless-N 1000 BGN, REV=0x6C [ 2266.578916] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S [ 2266.600709] iwlwifi 0000:04:00.0: device EEPROM VER=0x15d, CALIB=0x6 [ 2266.600712] iwlwifi 0000:04:00.0: Device SKU: 0X50 [ 2266.600713] iwlwifi 0000:04:00.0: Valid Tx ant: 0X1, Valid Rx ant: 0X3 [ 2266.600727] iwlwifi 0000:04:00.0: Tunable channels: 13 802.11bg, 0 802.11a channels [ 2266.605978] iwlwifi 0000:04:00.0: loaded firmware version 39.31.5.1 build 35138 [ 2266.606331] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs' [ 2266.614179] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S [ 2266.681541] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S Solutions I tried: rfkill list all 0: dell-wifi: Wireless LAN Soft blocked: no Hard blocked: no 2: phy0: Wireless LAN Soft blocked: no Hard blocked: no echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf options iwlwifi 11n_disable=1 sudo modprobe -rfv iwlwifi WARNING: All config files need .conf: /etc/modprobe.d/blacklist, it will be ignored in a future release. rmmod /lib/modules/3.2.0-24-generic/kernel/drivers/net/wireless/iwlwifi/iwlwifi.ko rmmod /lib/modules/3.2.0-24-generic/kernel/net/mac80211/mac80211.ko rmmod /lib/modules/3.2.0-24-generic/kernel/net/wireless/cfg80211.ko sudo modprobe iwlwifi WARNING: All config files need .conf: /etc/modprobe.d/blacklist, it will be ignored in a future release. replacing iwlwifi-1000-5.ucode (current driver) against iwlwifi-1000-3.ucode sudo jockey-gtk: (jockey-gtk:2493): Gtk-CRITICAL **: gtk_icon_set_render_icon_pixbuf: assertion icon_set != NULL' failed (jockey-gtk:2493): Gtk-CRITICAL **: gtk_icon_set_render_icon_pixbuf: assertion icon_set != NULL' failed nothing is listet in "Additional drivers" (german: "Zusätzliche Treiber"). gksudo gedit /etc/modprobe.d/blacklist.conf add "blacklist acer_wmi" Any help would be appreciated very much. Thanks!!

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• How to list missing partitions?

  - by celebrimbor

  I have installed Ubuntu on one of my partition and Crunchbang on the other partition. As I wanted to make some continuous space, I moved Crunchbang partition and then checked fdisk output which looks like this Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc7996dfa Device Boot Start End Blocks Id System /dev/sda1 * 63 80324 40131 de Dell Utility /dev/sda4 81918 625139711 312528897 f W95 Ext'd (LBA) /dev/sda5 81920 211816447 105867264 83 Linux /dev/sda6 299100160 341043199 20971520 83 Linux /dev/sda7 341045248 625139711 142047232 7 HPFS/NTFS/exFAT I cannot see sda2 and sda3 partition. How to find them?

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• Immutable Method in Java

  - by Chris Okyen

  In Java, there is the final keyword in lieu of the const keyword in C and C++. In the latter languages there are mutable and immutable methods such as stated in the answer by Johannes Schaub - litb to the question How many and which are the uses of “const” in C++? Use const to tell others methods won't change the logical state of this object. struct SmartPtr { int getCopies() const { return mCopiesMade; } }ptr1; ... int var = ptr.getCopies(); // returns mCopiesMade and is specified that to not modify objects state. How is this performed in Java?

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• Difference between a pseudo code and algorithm?

  - by Vamsi Emani

  Technically, Is there a difference between these two words or can we use them interchangeably? Both of them more or less describe the logical sequence of steps that follow in solving a problem. ain't it? SO why do we actually use two such words if they are meant to talk of the same? Or, In case if they aren't synonymous words, What is it that differentiates them? In what contexts are we supposed to use the word pseudo code vs the word algorithm? Thanks.

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