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• ODI 12c - Loading Files into Oracle, community post from ToadWorld

  - by David Allan

  There's a complete soup to nuts post from Deepak Vohra on the Oracle community pages of ToadWorld on loading a fixed length file into the Oracle database. This post is interesting from a few fronts; firstly this is the out of the box experience, no specialized KMs so just basic integration from getting the software installed to running a mapping. Also it demonstrates fixed length file integration including how to use the ODI UI to define the fields and pertinent properties.  Check the blog post out below.... http://www.toadworld.com/platforms/oracle/w/wiki/10935.loading-text-file-data-into-oracle-database-12c-with-oracle-data-integrator-12c.aspx Hopefully you also find this useful, many thanks to Deepak for sharing his experiences. You could take this example further and illustrate how to load into Oracle using the LKM File to Oracle via External table knowledge module which will perform much better and also leverage such things as using wildcards for loading many files into the 12c database.

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• Microsoft Patches Bugs, Improves Visual Studio 2012

  First, let's talk about the bug patches. Programs getting fixes include Windows, Internet Explorer, Office, the .NET Framework, Microsoft Dynamics AX and Microsoft Visual Basic. You can read the full security advisory. Out of the seven bulletins containing the fixes, three were deemed critical, which means a hacker could exploit an unpatched system by remotely executing malicious code. The remaining four were dubbed important; if exploited, they could give an attacker elevated privileges. Multiple versions of the Windows operating system and Internet Explorer should receive these patches....

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• BlueNES: A Bluetooth Connector for Classic NES Controllers

  - by Jason Fitzpatrick

  If you’re looking for a DIY way to hook up your classic Nintendo controllers for use in modern emulation programs, this hack allows you to use them without modifying the original casing or cables. Courtesy of Evan Dustin, we find this guide on hacking apart a broken NES unit (to get the basic parts like the port connectors) and then binding it all together with an Arduino board. Check out the video above to see it in action and then hit up the link below to check out the notes on the YouTube video for additional information including parts and code. BluesNES: Bluetooth NES Controller [via Hack A Day] HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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• Addressing a variable in VB

  - by Jeff

  Why doesn't Visual Basic.NET have the addressof operator like C#? In C#, one can int i = 123; int* addr = &i; But VB has no equivalent counter part. It seems like it should be important. UPDATE Since there's some interest, Im copying my response to Strilanc below. The case I ran into didnt necessitate pointers by any means, but I was trying to trouble shoot a unit test that was failing and there was some confusion over whether or not an object being used at one point in the stack was the same object as an object several methods away.

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• Strategies for very fast delivery of webpages.

  - by Cherian

  I run a website Cucumbertown with an initial pay load of nearly 9KB zipped. All my js is delayed loaded with requirejs and modernizer is the only exception. Now all my webpages are Nginx cached and only 10-15% hits go to the backend proxy. And the cache is invalidated by logged in users as proxy_cache_bypass. So for an anonymous user its nearly always a cache hit. I have some basic OS tuning with default via ip dev eth0 initcwnd 15 net.ipv4.tcp_slow_start_after_idle 0 Despite an all cache & large initcwnd my pages still take 2.5 – 3 seconds. I have a yslow score of And page speed at Are there strategies that can help deliver webpages even faster than this? Deliver pages at 1+ second time for 10KB payload? Notes: My servers run of a fairly good data center from Linode at Fremont.

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• NDepend 4 – First Steps

  - by Ricardo Peres

  Introduction Thanks to Patrick Smacchia I had the chance to test NDepend 4. I can only say: awesome! This will be the first of a series of posts on NDepend, where I will talk about my discoveries. Keep in mind that I am just starting to use it, so more experienced users may find these too basic, I just hope I don’t say anything foolish! I must say that I am in no way affiliated with NDepend and I never actually met Patrick. Installation No installation program – a curious decision, I’m not against it -, just unzip the files to a folder and run the executable. It will optionally register itself with Visual Studio 2008, 2010 and 11 as well as RedGate’s Reflector; also, it automatically looks for updates. NDepend can either be used as a stand-alone program (with or without a GUI) or from within Visual Studio or Reflector. Getting Started One thing that really pleases me is the Getting Started section of the stand-alone, with links to pages on NDepend’s web site, featuring detailed explanations, which usually include screenshots and small videos (<5 minutes). There’s also an How do I with hierarchical navigation that guides us to through the major features so that we can easily find what we want. Usage There are two basic ways to use NDepend: Analyze .NET solutions, projects or assemblies; Compare two versions of the same assembly. I have so far not used NDepend to compare assemblies, so I will first talk about the first option. After selecting a solution and some of its projects, it generates a single HTML page with an highly detailed report of the analysis it produced. This includes some metrics such as number of lines of code, IL instructions, comments, types, methods and properties, the calculation of the cyclomatic complexity, coupling and lots of others indicators, typically grouped by type, namespace and assembly. The HTML also includes some nice diagrams depicting assembly dependencies, type and method relative proportions (according to the number of IL instructions, I guess) and assembly analysis relating to abstractness and stability. Useful, I would say. Then there’s the rules; NDepend tests the target assemblies against a set of more than 120 rules, grouped in categories Code Quality, Object Oriented Design, Design, Architecture and Layering, Dead Code, Visibility, Naming Conventions, Source Files Organization and .NET Framework Usage. The full list can be configured on the application, and an explanation of each rule can be found on the web site. Rules can be validated, violated and violated in a critical manner, and the HTML will contain the violated rules, their queries – more on this later - and results. The HTML uses some nice JavaScript effects, which allow paging and sorting of tables, so its nice to use. Similar to the rules, there are some queries that display results for a number (about 200) questions grouped as Object Oriented Design, API Breaking Changes (for assembly version comparison), Code Diff Summary (also for version comparison) and Dead Code. The difference between queries and rules is that queries are not classified as passes, violated or critically violated, just present results. The queries and rules are expressed through CQLinq, which is a very powerful LINQ derivative specific to code analysis. All of the included rules and queries can be enabled or disabled and new ones can be added, with intellisense to help. Besides the HTML report file, the NDepend application can be used to explore all analysis results, compare different versions of analysis reports and to run custom queries. Comparison to Other Analysis Tools Unlike StyleCop, NDepend only works with assemblies, not source code, so you can’t expect it to be able to enforce brackets placement, for example. It is more similar to FxCop, but you don’t have the option to analyze at the IL level, that is, other that the number of IL instructions and the complexity. What’s Next In the next days I’ll continue my exploration with a real-life test case. References The NDepend web site is http://www.ndepend.com/. Patrick keeps an updated blog on http://codebetter.com/patricksmacchia/ and he regularly monitors StackOverflow for questions tagged NDepend, which you can find on http://stackoverflow.com/questions/tagged/ndepend. The default list of CQLinq rules, queries and statistics can be found at http://www.ndepend.com/DefaultRules/webframe.html. The syntax itself is described at http://www.ndepend.com/Doc_CQLinq_Syntax.aspx and its features at http://www.ndepend.com/Doc_CQLinq_Features.aspx.

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• QotD - Nicolas de Loof on AdoptOpenJDK

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

  The AdoptOpenJDK program is an initiative to get as many Java users as possible to try the OpenJDK 8 preview builds, so that feedback is collected before JDK 8 is officially released. There are many ways to contribute to this program (as explained on the wiki), but the most basic one is to start testing your own project on the Java 8 platform. CloudBees can help you there, as we just made OpenJDK 8 (preview) available on DEV@cloud so that you can configure a build job to check project compatibility. We will upgrade the JDK for all recent preview builds until JDK 8 is finalNicolas de Loof, Support Engineer at Cloudbees in a blog post on AdoptOpenJDK.

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• Hard drive mounted at / , duplicate mounted hard drive after using MountManager

  - by HellHarvest

  possible duplicate post I'm running 12.04 64bit. My system is a dual boot for both Ubuntu and Windows7. Both operating systems are sharing the drive named "Elements". My volume named "Elements" is a 1TB SATA NTFS hard drive that shows up twice in the side bar in nautilus. One of the icons is functional and even has the convenient "eject" icon next to it. Below is a picture of the left menu in Nautilus, with System Monitor-File Systems tab open on top of it. Can someone advise me about how to get rid of this extra icon? I think the problem is much more deep-rooted than just a GUI glitch on Nautilus' part. The other icon does nothing but spit out the following error when I click on it (image below). This only happened AFTER I tried using Mount Manager to automate mounting the drive at start up. I've already uninstalled Mount Manager, and restarted, but the problem didn't go away. The hard drive does mount automatically now, so I guess that's cool. But now, every time I boot up now and open Nautilus, BOTH of these icons appear, one of which is fictitious and useless. According to the image above and the outputs of several other commands, it appears to be mounted at / In which case, no matter where I am in Nautilus when I try to click on that icon, of course it will tell me that that drive is in use by another program... Nautilus. I'm afraid of trying to unmount this hard drive (sdb6) because of where it appears to be mounted. I'm kind of a noob, and I have this gut feeling that tells me trying to unmount a drive at / will destroy my entire file system. This fear was further strengthened by the output of "$ fsck" at the very bottom of this post. Error immediately below when that 2nd "Elements" hard drive is clicked in Nautilus: Unable to mount Elements Mount is denied because the NTFS volume is already exclusively opened. The volume may be already mounted, or another software may use it which could be identified for example by the help of the 'fuser' command. It's odd to me that that error message above claims that it's an NTFS volume when everything else tell me that it's an ext4 volume. The actual hard drive "Elements" is in fact an NTFS volume. Here's the output of a few commands and configuration files that may be of interest: $ fuser -a / /: 2120r 2159rc 2160rc 2172r 2178rc 2180rc 2188r 2191rc 2200rc 2203rc 2205rc 2206r 2211r 2212r 2214r 2220r 2228r 2234rc 2246rc 2249rc 2254rc 2260rc 2261r 2262r 2277rc 2287rc 2291rc 2311rc 2313rc 2332rc 2334rc 2339rc 2343rc 2344rc 2352rc 2372rc 2389rc 2422r 2490r 2496rc 2501rc 2566r 2573rc 2581rc 2589rc 2592r 2603r 2611rc 2613rc 2615rc 2678rc 2927r 2981r 3104rc 4156rc 4196rc 4206rc 4213rc 4240rc 4297rc 5032rc 7609r 7613r 7648r 9593rc 18829r 18833r 19776r $ sudo df -h Filesystem Size Used Avail Use% Mounted on /dev/sdb6 496G 366G 106G 78% / udev 2.0G 4.0K 2.0G 1% /dev tmpfs 791M 1.5M 790M 1% /run none 5.0M 0 5.0M 0% /run/lock none 2.0G 672K 2.0G 1% /run/shm /dev/sda1 932G 312G 620G 34% /media/Elements /home/solderblob/.Private 496G 366G 106G 78% /home/solderblob /dev/sdb2 188G 100G 88G 54% /media/A2B24EACB24E852F /dev/sdb1 100M 25M 76M 25% /media/System Reserved $ sudo fdisk -l 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 / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00093cab Device Boot Start End Blocks Id System /dev/sda1 2048 1953519615 976758784 7 HPFS/NTFS/exFAT Disk /dev/sdb: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 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: 0x000e8d9b Device Boot Start End Blocks Id System /dev/sdb1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sdb2 206848 392378768 196085960+ 7 HPFS/NTFS/exFAT /dev/sdb3 392380414 1465147391 536383489 5 Extended /dev/sdb5 1456762880 1465147391 4192256 82 Linux swap / Solaris /dev/sdb6 392380416 1448374271 527996928 83 Linux /dev/sdb7 1448376320 1456758783 4191232 82 Linux swap / Solaris Partition table entries are not in disk order $ cat /etc/fstab # <file system> <mount point> <type> <options> <dump> <pass> UUID=77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e / ext4 defaults 0 1 UUID=F6549CC4549C88CF /media/Elements ntfs-3g users 0 0 $ sudo blkid /dev/sda1: LABEL="Elements" UUID="F6549CC4549C88CF" TYPE="ntfs" /dev/sdb1: LABEL="System Reserved" UUID="5CDE130FDE12E156" TYPE="ntfs" /dev/sdb2: UUID="A2B24EACB24E852F" TYPE="ntfs" /dev/sdb6: UUID="77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e" TYPE="ext4" $ sudo blkid -c /dev/null (appears to be exactly the same as above) /dev/sda1: LABEL="Elements" UUID="F6549CC4549C88CF" TYPE="ntfs" /dev/sdb1: LABEL="System Reserved" UUID="5CDE130FDE12E156" TYPE="ntfs" /dev/sdb2: UUID="A2B24EACB24E852F" TYPE="ntfs" /dev/sdb6: UUID="77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e" TYPE="ext4" $ mount /dev/sdb6 on / type ext4 (rw) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) /dev/sda1 on /media/Elements type fuseblk (rw,noexec,nosuid,nodev,allow_other,blksize=4096) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) /home/solderblob/.Private on /home/solderblob type ecryptfs (ecryptfs_check_dev_ruid,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs,ecryptfs_sig=76a47b0175afa48d,ecryptfs_fnek_sig=391b2d8b155215f7) gvfs-fuse-daemon on /home/solderblob/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=solderblob) /dev/sdb2 on /media/A2B24EACB24E852F type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096) /dev/sdb1 on /media/System Reserved type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096) $ ls -a . A2B24EACB24E852F Ubuntu 12.04.1 LTS amd64 .. Elements System Reserved $ cat /proc/mounts rootfs / rootfs rw 0 0 sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0 proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0 udev /dev devtmpfs rw,relatime,size=2013000k,nr_inodes=503250,mode=755 0 0 devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0 tmpfs /run tmpfs rw,nosuid,relatime,size=809872k,mode=755 0 0 /dev/disk/by-uuid/77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e / ext4 rw,relatime,user_xattr,acl,barrier=1,data=ordered 0 0 none /sys/fs/fuse/connections fusectl rw,relatime 0 0 none /sys/kernel/debug debugfs rw,relatime 0 0 none /sys/kernel/security securityfs rw,relatime 0 0 none /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0 none /run/shm tmpfs rw,nosuid,nodev,relatime 0 0 /dev/sda1 /media/Elements fuseblk rw,nosuid,nodev,noexec,relatime,user_id=0,group_id=0,allow_other,blksize=4096 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,nosuid,nodev,noexec,relatime 0 0 /home/solderblob/.Private /home/solderblob ecryptfs rw,relatime,ecryptfs_fnek_sig=391b2d8b155215f7,ecryptfs_sig=76a47b0175afa48d,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs 0 0 gvfs-fuse-daemon /home/solderblob/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,relatime,user_id=1000,group_id=1000 0 0 /dev/sdb2 /media/A2B24EACB24E852F fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 /dev/sdb1 /media/System\040Reserved fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 gvfs-fuse-daemon /root/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,relatime,user_id=0,group_id=0 0 0 $ fsck fsck from util-linux 2.20.1 e2fsck 1.42 (29-Nov-2011) /dev/sdb6 is mounted. WARNING!!! The filesystem is mounted. If you continue you ***WILL*** cause ***SEVERE*** filesystem damage. Do you really want to continue<n>? no check aborted.

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• Oracle Social Network Developer Challenge: Bezzotech

  - by Kellsey Ruppel

  Originally posted by Jake Kuramoto on The Apps Lab blog. I’ve covered all the entries we had for the Oracle Social Network Developer Challenge, the winners, Dimitri and Martin, HarQen, TEAM Informatics and John Sim from Fishbowl Solutions, and today, I’m giving you bonus coverage. Friend of the ‘Lab, Bex Huff (@bex) from Bezzotech (@bezzotech), had an interesting OpenWorld. He rebounded from an allergic reaction to finish his entry, Honey Badger, only to have his other OpenWorld commitments make him unable to present his work. Still, he did a bunch of work, and I want to make sure everyone knows about the Honey Badger. If you’re wondering about the name, it’s a meme; “honey badger don’t care.” Bex tackled a common problem with social tools by adding game mechanics to create an incentive for people to keep their profiles updated. He used a Hot-or-Not style comparison app that poses expertise questions and awards a badge to the winner. Questions are based on whatever attributes the business wants to emphasize. The goal is to find the mavens in an organization, give them praise and recognition, ideally creating incentive for everyone to raise their games. In his own words: There is a real information quality problem in social networks. In last year’s keynote, Larry Elison demonstrated how to use the social network to track down resources that have the skill sets needed for specific projects. But how well would that work in real life? People usually update that information with the basic profile information, but they rarely update their profiles with latest news items, projects, customers, or skills. It’s a pain. Or, put another way, when was the last time you updated your LinkedIn profile? Enter the Honey Badger! This is a example of a comparator app that gamifies the way people keep their profiles updated, which ensures higher quality data in the social network. An administrator comes up with a series of important questions: Who is a better communicator? Who is a better Java programmer? Who is a better team player? And people would have a space in their profile to give a justification as to why they have these skills. The second part of the app is the comparator. It randomly shows two people, their names, and their justification for why they have these skills. You will click on one of them to “vote” for them, then on the next page you will see the results from the previous match, and get 2 new people to vote on. Anybody with a winning score wins a “Honey Badge” to be displayed on their profile page, which proudly states that their peers agree that this person has those skills. Once a badge is won, it will be jealously guarded. The longer your go without updating your profile, the more likely it is that you will lose your badge. This “loss aversion” is well known in psychology, and is a strong incentive for people to keep their profiles up to date. If a user sees their rank drop from 90% to 60%, they will find the time to update their justification! Unfortunately, during the hackathon we were not allowed to modify the schema to allow for additional fields such as “justification.” So this hack is limited to just the one basic question: who is the bigger Honey Badger? Here are some shots of the Honey Badger application: #gallery-1 { margin: auto; } #gallery-1 .gallery-item { float: left; margin-top: 10px; text-align: center; width: 33%; } #gallery-1 img { border: 2px solid #cfcfcf; } #gallery-1 .gallery-caption { margin-left: 0; } Thanks to Bex and everyone for participating in our challenge. Despite very little time to promote this event, we had a great turnout and creative and useful entries. The amount of work required to put together these final entries was significant, especially during a conference, and the judges and all of us involved were impressed at how much work everyone was able to do. Congrats to everyone, pat yourselves on the back. Stay tuned if you’re interested in challenges like these. We’ll likely be running similar events in the not-so-distant future.

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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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• Network Access: I can't access 192.168.1.101 from 192.168.1.102.

  - by takpar

  Hi, I'm running Ubuntu 10.04 on my PC with IP 192.168.1.101. every thing work fine, e.g. my web server is running and I can see http://localhost/ or http://192.168.1.101 properly. But the problem is that I cannot see my PC from my laptop at 192.168.1.102 e.g. at my laptop http://192.168.1.101 gives Connection timed out in browser. or trying to telnet on any port leads to: telnet: Unable to connect to remote host: Connection timed out laptop is running a fresh install of Ubuntu as well and there is no setup for firewall stuff in both computers. PS: Both computers can ping each other well. The router is a cicso linksys wireless ADSL modem. Currently, I can connect to FTP server on the Windows running on 192.168.1.102 from 192.168.1.101 without problem. Theses are commands ran on my PC, 192.168.1.101: ifconfig: adp@adp-desktop:~$ ifconfig eth0 Link encap:Ethernet HWaddr 00:26:18:e1:8e:cf inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::226:18ff:fee1:8ecf/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1831935 errors:0 dropped:0 overruns:0 frame:0 TX packets:1493786 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1996855925 (1.9 GB) TX bytes:215288238 (215.2 MB) Interrupt:27 Base address:0xa000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:951742 errors:0 dropped:0 overruns:0 frame:0 TX packets:951742 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:494351095 (494.3 MB) TX bytes:494351095 (494.3 MB) vmnet1 Link encap:Ethernet HWaddr 00:50:46:c0:00:01 inet addr:192.168.91.1 Bcast:192.168.91.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:1/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:50 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) vmnet8 Link encap:Ethernet HWaddr 00:50:46:c0:00:08 inet addr:192.168.156.1 Bcast:192.168.156.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:51 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) port 80 is set to 0.0.0.0 well: adp@adp-desktop:~$ netstat -ln | grep 'LISTEN ' tcp 0 0 127.0.0.1:52815 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4559 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4369 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:7634 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5269 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5280 0.0.0.0:* LISTEN tcp 0 0 127.0.1.1:7777 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:33601 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5222 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN tcp6 0 0 :::139 :::* LISTEN tcp6 0 0 ::1:631 :::* LISTEN tcp6 0 0 :::445 :::* LISTEN /etc/hosts.deny is empty: adp@adp-desktop:~$ cat /etc/hosts.deny # /etc/hosts.deny: list of hosts that are _not_ allowed to access the system. # See the manual pages hosts_access(5) and hosts_options(5). # # Example: ALL: some.host.name, .some.domain # ALL EXCEPT in.fingerd: other.host.name, .other.domain # # If you're going to protect the portmapper use the name "portmap" for the # daemon name. Remember that you can only use the keyword "ALL" and IP # addresses (NOT host or domain names) for the portmapper, as well as for # rpc.mountd (the NFS mount daemon). See portmap(8) and rpc.mountd(8) # for further information. # # The PARANOID wildcard matches any host whose name does not match its # address. # # You may wish to enable this to ensure any programs that don't # validate looked up hostnames still leave understandable logs. In past # versions of Debian this has been the default. # ALL: PARANOID netstat -l: adp@adp-desktop:~$ netstat -l Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:52815 *:* LISTEN tcp 0 0 *:hylafax *:* LISTEN tcp 0 0 *:www *:* LISTEN tcp 0 0 *:4369 *:* LISTEN tcp 0 0 localhost:7634 *:* LISTEN tcp 0 0 *:ftp *:* LISTEN tcp 0 0 *:xmpp-server *:* LISTEN tcp 0 0 localhost:ipp *:* LISTEN tcp 0 0 *:smtp *:* LISTEN tcp 0 0 *:5280 *:* LISTEN tcp 0 0 adp-desktop:7777 *:* LISTEN tcp 0 0 *:33601 *:* LISTEN tcp 0 0 *:xmpp-client *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN tcp6 0 0 localhost:ipp [::]:* LISTEN tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN udp 0 0 *:bootpc *:* udp 0 0 *:mdns *:* udp 0 0 *:47467 *:* udp 0 0 192.168.1.10:netbios-ns *:* udp 0 0 192.168.91.1:netbios-ns *:* udp 0 0 192.168.156.:netbios-ns *:* udp 0 0 *:netbios-ns *:* udp 0 0 192.168.1.1:netbios-dgm *:* udp 0 0 192.168.91.:netbios-dgm *:* udp 0 0 192.168.156:netbios-dgm *:* udp 0 0 *:netbios-dgm *:* raw 0 0 *:icmp *:* 7 netstat -rn: adp@adp-desktop:~$ netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.91.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet1 192.168.156.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet8 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 commands on the laptop, 192.168.1.102: ifconfig: root@fakeuser-laptop:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:1c:33:a2:31:15 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:21 eth1 Link encap:Ethernet HWaddr 00:2d:d9:3e:1f:6c inet addr:192.168.1.102 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::21d:d9ff:fe3e:1f6c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5681 errors:0 dropped:0 overruns:0 frame:10313 TX packets:6717 errors:6 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4055251 (4.0 MB) TX bytes:779308 (779.3 KB) Interrupt:18 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:206 errors:0 dropped:0 overruns:0 frame:0 TX packets:206 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:15172 (15.1 KB) TX bytes:15172 (15.1 KB) netstat -rn: root@fakeuser-laptop:~# netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1

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• What have we lost from computers 20 years ago

  - by Martin Beckett

  Following the theme of - I can't believe computers used floppy disks and did you have debuggers 20 years ago - questions (and because even putting my age in hex I don't look young anymore). What have we lost from computers 20years ago? VMS versioning file system. Make a mistake, no problem myprog.cpp;5 is still there. Home computers that powered up to give you a wordprocessor or a basic prompt in <0.5sec User ports, serial ports and ADCs that you could control things with - without an arduino APIs that actually did what they said (even DOS interrupts), without having to guess and experiment your way through layers of frameworks.

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• Practical Meta Programming System (MPS)

  - by INTPnerd

  This is in regards to Meta Programming System or MPS by JetBrains. Thus far, from my efforts to learn how to use MPS, I have only learned its basic purpose and that it is very complex. Is MPS worth learning? Is there anyone who already effectively uses MPS to create their own languages and editors for those languages and uses these created editors as their primary way of programming? If so, what types of programs have they made with this? What are the advantages and disadvantages of working with MPS? What is the best way to learn MPS?

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• Gnome panel not found

  - by emilbochnik

  Hi I installed the Ubuntu 10.10 on my laptop. 1st time Ubuntu user ever. After successful installation only panel on top with small ubuntu logo on left and system/connections, time, keyboard, volume icons/ on right. No menu and not able to create menu. Right click on the panel - no options. I tried everything, but it could be the most basic think as i have no experience with ubuntu. Please can you help me to resolve this issue. thank you bochnik

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• XNA - Drawing 2D Primitives (Boxes) and Understanding Matrices in Computer Graphics

  - by MintyAnt

  I have two issues which I wish to solve by creating 2D primitives in XNA. In my game, I wish to have a "debug mode" which will draw a red box around all hitboxes in the game (Red outline, transparent inside). This would allow us to see where the hitboxes are being drawn AND still have the sprite graphics being drawn. I wish to further understand how matrices work within computer graphics. I have a basic theoretical grasp of how they work, but I really just want to apply some of my knowledge or find a good tutorial on it. To do this, I wish to draw my own 2D primitives (With Vertex3's) and apply different transormation matrices to them. I was trying to find a tutorial on drawing primitives using Direct3D, but most tutorials are only for c++, and just tell me to use XNA's Spritebatch. I wish to have more control over my program than just with Spritebatch. Any Help on using Direct3D or any other suggestions would greatly be appreciated. Thank you.

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• It's 2011-Do You Know Where Your Children Are?

  - by andyleonard

  Introduction This is not a post about children. I was feeling plucky when I wrote this post at the end of last year. Sometimes when I feel plucky I'm inspired to create awesome blog post titles and ideas. Other times, this happens. 2011 Is Here! I was born in 1963. As I child I watched Neil Armstrong and Buzz Aldrin walk on the moon while Walter Cronkite narrated. At 11, I was fortunate enough to live next door to an engineer who taught me Motorola 6800 machine code and then BASIC . I have a long...(read more)

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• Does Open Source lead to bad coding?

  - by David Conde

  I have a thought that I tried asking at SO, but didnt seem like the appropriate place. I think that source sites like Google Code, GitHub, SourceForge... have played a major role in the history of programming. However, I found that there is another bad thing to these kind of sites and that is you may just "copy" code from almost anyone, not knowing if it is good(tested) source or not. This line of thought has taken me to believe that source code websites tend to lead many developers (most likely unexperienced) to copy/paste massive amounts of code, which I find just wrong. I really dont know how to focus the question well, but basic thought would be: Is this ok? Is Open Source contributing to that or I'm just seeing ghosts... Hope people get interested because I think this is an important theme.

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• How are Programing Language Designed?

  - by Anteater7171

  After doing a bit of programing, I've become quite curious on language design itself. I'm still a novice (I've been doing it for about a year), so the majority of my code pertains to only two fields (GUI design in Python and basic algorithms in C/C++). I have become intrigued with how the actual languages themselves are written. I mean this in both senses. Such as how it was literally written (ie, what language the language was written in). As well as various features like white spacing (Python) or object orientation (C++ and Python). Where would one start learning how to write a language? What are some of the fundamentals of language design, things that would make it a "complete" language?

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• ContentManager in XNA cant find any XML

  - by user36385

  Im making a game in XNA 4 and this is the first time I'm using the Content loader to initialize a simple class with a XML file, but no matter how many guide I follow, or how simple or complicated is my XML File the ContentManager cant find the file; the Debug keep telling me: "A first chance exception of type 'Microsoft.Xna.Framework.Content.ContentLoadException' occurred in Microsoft.Xna.Framework.dll". I'm really confuse because I can load SpriteFonts and Texture2D without a problem ... I create the following XML (the most basic Xna XML): <?xml version="1.0" encoding="utf-8" ?> <XnaContent> <Asset Type="System.String">Hello</Asset> </XnaContent> and I try to load it in the LoadContent method in my main class like this: System.String hello = Content.Load<System.String>("NewXmlFile"); There is something I'm doing wrong? I really appreciate your help

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• Starting off with web dev with php

  - by pavan kumar

  I'm currently working with Java / C++. I'm interested in web development and am planning to shift my stream. I heard that PHP is a good platform to start off and also it does not require that much of knowledge in technologies like JSP / Servlets or frameworks like springs / struts / hibernate. I have basic ideas about HTML and Javascript as well. I have gone through previous posts in SO and found out the relevant resources as well: http://net.tutsplus.com/tutorials/php/the-best-way-to-learn-php/ http://www.webhostingtalk.com/archive/index.php/t-1028265.html http://www.killerphp.com/ http://phpforms.net/tutorial/tutorial.html http://www.php5-tutorial.com/ etc. Now, my question is: I heard of PHP frameworks like CodeIgniter, Zend Frameworkd and Yii. Doesn't learning PHP & MySql implicitly makes us aware of these frameworks? Am I making a good choice in stating with PHP? Is it a good idea to shift streams?

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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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• Recommendations for books and training resources covering for Design for Programmers

  - by Jon Hopkins

  Off the back of one of the answers to this question (currently the second highest scoring), it made me think, what's the best way to get developers up to speed on good basic design principals. I'm not talking about making them into graphic designers but some developers almost take pride in ugly UIs, seeing them as unimportant next to the functionality. What primarily interested in are the graphic design elements rather than the usability aspects which is pretty well covered by books such as Don't Make Me Think. Use of white space, emphasis, font selection and a million other things I'm probably not even aware of. I know people are often seen as artistic or not artistic but surely the basics can be taught and someone has written a book covering this?

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• SQL SERVER – Weekly Series – Memory Lane – #034

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 UDF – User Defined Function to Strip HTML – Parse HTML – No Regular Expression The UDF used in the blog does fantastic task – it scans entire HTML text and removes all the HTML tags. It keeps only valid text data without HTML task. This is one of the quite commonly requested tasks many developers have to face everyday. De-fragmentation of Database at Operating System to Improve Performance Operating system skips MDF file while defragging the entire filesystem of the operating system. It is absolutely fine and there is no impact of the same on performance. Read the entire blog post for my conversation with our network engineers. Delay Function – WAITFOR clause – Delay Execution of Commands How do you delay execution of the commands in SQL Server – ofcourse by using WAITFOR keyword. In this blog post, I explain the same with the help of T-SQL script. Find Length of Text Field To measure the length of TEXT fields the function is DATALENGTH(textfield). Len will not work for text field. As of SQL Server 2005, developers should migrate all the text fields to VARCHAR(MAX) as that is the way forward. Retrieve Current Date Time in SQL Server CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} There are three ways to retrieve the current datetime in SQL SERVER. CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} Explanation and Comparison of NULLIF and ISNULL An interesting observation is NULLIF returns null if it comparison is successful, whereas ISNULL returns not null if its comparison is successful. In one way they are opposite to each other. Here is my question to you - How to create infinite loop using NULLIF and ISNULL? If this is even possible? 2008 Introduction to SERVERPROPERTY and example SERVERPROPERTY is a very interesting system function. It returns many of the system values. I use it very frequently to get different server values like Server Collation, Server Name etc. SQL Server Start Time We can use DMV to find out what is the start time of SQL Server in 2008 and later version. In this blog you can see how you can do the same. Find Current Identity of Table Many times we need to know what is the current identity of the column. I have found one of my developers using aggregated function MAX () to find the current identity. However, I prefer following DBCC command to figure out current identity. Create Check Constraint on Column Some time we just need to create a simple constraint over the table but I have noticed that developers do many different things to make table column follow rules than just creating constraint. I suggest constraint is a very useful concept and every SQL Developer should pay good attention to this subject. 2009 List Schema Name and Table Name for Database This is one of the blog post where I straight forward display script. One of the kind of blog posts, which I still love to read and write. Clustered Index on Separate Drive From Table Location A table devoid of primary key index is called heap, and here data is not arranged in a particular order, which gives rise to issues that adversely affect performance. Data must be stored in some kind of order. If we put clustered index on it then the order will be forced by that index and the data will be stored in that particular order. Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. 2010 Data Pages in Buffer Pool – Data Stored in Memory Cache One of my earlier year article, which I still read it many times and point developers to read it again. It is clear from the Resultset that when more than one index is used, datapages related to both or all of the indexes are stored in Memory Cache separately. TRANSACTION, DML and Schema Locks Can you create a situation where you can see Schema Lock? Well, this is a very simple question, however during the interview I notice over 50 candidates failed to come up with the scenario. In this blog post, I have demonstrated the situation where we can see the schema lock in database. 2011 Solution – Puzzle – Statistics are not updated but are Created Once In this example I have created following situation: Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated Auto Update Statistics and Auto Create Statistics for database is TRUE Now I have requested two things in the example 1) Why this is happening? 2) How to fix this issue? Selecting Domain from Email Address This is a straight to script blog post where I explain how to select only domain name from entire email address. Solution – Generating Zero Without using Any Numbers in T-SQL How to get zero digit without using any digit? This is indeed a very interesting question and the answer is even interesting. Try to come up with answer in next 10 minutes and if you can’t come up with the answer the blog post read this post for solution. 2012 Simple Explanation and Puzzle with SOUNDEX Function and DIFFERENCE Function In simple words - SOUNDEX converts an alphanumeric string to a four-character code to find similar-sounding words or names. DIFFERENCE function returns an integer value. The  integer returned is the number of characters in the SOUNDEX values that are the same. Read Only Files and SQL Server Management Studio (SSMS) I have come across a very interesting feature in SSMS related to “Read Only” files. I believe it is a little unknown feature as well so decided to write a blog about the same. Identifying Column Data Type of uniqueidentifier without Querying System Tables How do I know if any table has a uniqueidentifier column and what is its value without using any DMV or System Catalogues? Only information you know is the table name and you are allowed to return any kind of error if the table does not have uniqueidentifier column. Read the blog post to find the answer. Solution – User Not Able to See Any User Created Object in Tables – Security and Permissions Issue Interesting question – “When I try to connect to SQL Server, it lets me connect just fine as well let me open and explore the database. I noticed that I do not see any user created instances but when my colleague attempts to connect to the server, he is able to explore the database as well see all the user created tables and other objects. Can you help me fix it?” Importing CSV File Into Database – SQL in Sixty Seconds #018 – Video Here is interesting small 60 second video on how to import CSV file into Database. ColumnStore Index – Batch Mode vs Row Mode Here is the logic behind when Columnstore Index uses Batch Mode and when it uses Row Mode. A batch typically represents about 1000 rows of data. Batch mode processing also uses algorithms that are optimized for the multicore CPUs and increased memory throughput. Follow up – Usage of $rowguid and $IDENTITY This is an excellent follow up blog post of my earlier blog post where I explain where to use $rowguid and $identity.  If you do not know the difference between them, this is a blog with a script example. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• I'm building a theme for tumblr and the {HasPages} doesn't seem to work properly.

  - by Muhammad

  I've put the HTML draft of the theme so far, with minor CSS edits. Currently I have all the block posts and everything else that's essential to a tumblr theme but I can't seem to get the {HasPages} block to work properly. I've tested it on a different tumblr, also. There are pages created and I already have provided some basic CSS for it just in case. But there isn't anything showing up. Has anyone has this problem and if so, is there a solution I'm missing? The code to display the pages is included. {block:HasPages} <ul> <li><a href="/">Home</a></li> {block:Pages}<li><a href="{URL}">{Label}</a></li>{/block:Pages} </ul> {/block:HasPages} Also, is this a valid web masters' question. I'm not sure.

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• Python rpg adivce? [closed]

  - by nikita.utiu

  I have started coding an text rpg engine in python. I have basic concepts laid down, like game state saving, input, output etc. I was wondering how certain scripted game mechanics(eg. debuffs that increase damage received from a certain player or multiply damage by the number of hits received, overriding of the mobs default paths for certain events etc) are implemented usually implemented. Some code bases or some other source code would be useful(not necessarily python). Thanks in advance.

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