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  • Windows Firewall Software to Filter Transit Traffic

    - by soonts
    I need to test my networking code for Nintendo Wii under the conditions when some specific Internet server is not available. Wii is connected to my PC with crossover ethernet cable. PC has 2 NICs. PC is connected to hardware router with ethernet cable. The hardware router serves as NAT and has an internet connected to its uplink. I set the Wii to be in the same lan as PC by using Windows XP Network bridge. I can observe the WII network traffic using e.g. Wireshark sniffer. Is there a software firewall that can selectively filter out transit traffic? (e.g. block outgoing TCP connections to 123.45.67.89 to port 443) I tried Outpost Pro 2009 and Comodo. Outpost firewall blocks all transit traffic with it's implicit "block transit packet" rule. If the transit traffic is explicitly allowed by creating the system-wide low level rule, then it's allowed completely and no other filter can selectively block it. Comodo firewall only process rules when the packet has localhost's IP as either source or destination, allowing the rest of the traffic. Any ideas? Thanks in advance! P.S. Platform is Windows XP 32 bit, no other OSes is allowed, Windows ICS (Internet Connection Sharing) doesnt work since the Wii is unable to connect, becides I don't like the idea of adding one more level of NAT.

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  • How to create a software raid5 array without a spare

    - by Yannick M.
    I am trying to create a software raid5 array using mdadm: $ linux # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 --spare-devices=0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm: layout defaults to left-symmetric mdadm: chunk size defaults to 64K mdadm: array /dev/md0 started. However when inspecting /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 sdd1[4] sdc1[2] sdb1[1] sda1[0] 2930279808 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_] [>....................] recovery = 0.3% (2970496/976759936) finish=186.1min speed=87172K/sec unused devices: <none> It seems one drive isn't active, so I check the details of the array: /dev/md0: Version : 00.90.03 Creation Time : Tue Jul 21 16:29:53 2009 Raid Level : raid5 Array Size : 2930279808 (2794.53 GiB 3000.61 GB) Used Dev Size : 976759936 (931.51 GiB 1000.20 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Tue Jul 21 16:29:53 2009 State : clean, degraded, recovering Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 64K Rebuild Status : 0% complete UUID : ce8b2f40:821d003c:0027688e:a70977ec Events : 0.1 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 4 8 49 3 spare rebuilding /dev/sdd1 And it seems there are only 3 active devices, with one spare. Is it just me, or something wrong here?

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  • Converting software RAID1 to RAID10 for /boot

    - by luckytaxi
    Array info: /dev/md0 - /dev/sda1 and /dev/sdb1 /dev/md2 - /dev/sda2 and /dev/sdb2 Partition info: /boot - /dev/md0 / - /dev/md1 I have two drives that are setup as RAID1 using software RAID on Redhat. I added two additional drives (same size) and I would like to conver the RAID1 to a RAID10. The problem I'm having is adding the last drive to the array. I've gotten as far as creating a RAID10 with two missing devices but as soon as I add the last drive, all hell breaks loose. It seems /dev/sda1 is the culprit. What I'm not too sure about is how to create the RAID10. I've tried the following mdadm --create /dev/md2 --level=raid10 --raid-device=4 /dev/sdc1 missing /dev/sdd1 missing I then proceeded to fail /dev/sdb1 from /dev/md0 and added that partition to /dev/md2. I proceeded to install the MBR on EACH partition since boot resides on /dev/sdx1 on each drive. As a test, all is well, I'm able to boot back into the system once I do a quick reboot. Now, when I go add the last drive /dev/sda1, it breaks. I attempted to install grub on /dev/sda1 and I get the following ... grub> root (hd0,0) /dev/sda root (hd0,0) /dev/sda Filesystem type is ext2fs, partition type 0xfd grub> setup (hd0) setup (hd0) Checking if "/boot/grub/stage1" exists... no Checking if "/grub/stage1" exists... no Error 2: Bad file or directory type At this point, the array is hosed I believe. I rebooted the server and it refuses to boot.

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  • How to interrupt software raid resync?

    - by Adam5
    I want to interrupt a running resync operation on a debian squeeze software raid. (This is the regular scheduled compare resync. The raid array is still clean in such a case. Do not confuse this with a rebuild after a disk failed and was replaced.) How to stop this scheduled resync operation while it is running? Another raid array is "resync pending", because they all get checked on the same day (sunday night) one after another. I want a complete stop of this sunday night resyncing. [Edit: sudo kill -9 1010 doesn't stop it, 1010 is the PID of the md2_resync process] I would also like to know how I can control the intervals between resyncs and the remainig time till the next one. [Edit2: What I did now was to make the resync go very slow, so it does not disturb anymore: sudo sysctl -w dev.raid.speed_limit_max=1000 taken from http://www.cyberciti.biz/tips/linux-raid-increase-resync-rebuild-speed.html During the night I will set it back to a high value, so the resync can terminate. This workaround is fine for most situations, nonetheless it would be interesting to know if what I asked is possible. For example it does not seem to be possible to grow an array, while it is resyncing or resyncing "pending"]

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  • Growing a Linux software RAID5 array

    - by chrismetcalf
    On my home file server, I've got a 1.5TB software RAID5 array, built from four 500gb Western Digital drives. I've got a fifth drive that I usually run as a hot spare (but have out of the array at the moment), but if I can I'd like to add that to the array and grow it to 2TB since I'm running out of space. I Googled for guidance, but there seem to be a lot of differing opinions out there (many of them probably now out-of-date) as to whether or not that is possible and/or smart. What's the right way to go about this, or should I start looking into building a new array with more space? Version details: %> cat /etc/issue Debian GNU/Linux 5.0 \n \l %> uname -a Linux magrathea 2.6.26-1-686-bigmem #1 SMP Sat Jan 10 19:13:22 UTC 2009 i686 GNU/Linux %> /sbin/mdadm --version mdadm - v2.6.7.2 - 14th November 2008 %> cat /proc/mdstat Personalities : [raid1] [raid6] [raid5] [raid4] md1 : active raid1 hdc1[0] hdd1[1] 293033536 blocks [2/2] [UU] md0 : active raid5 sde1[3] sda1[0] sdc1[2] sdb1[1] 1465151808 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

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  • Reusing slot numbers in Linux software RAID arrays

    - by thkala
    When a hard disk drive in one of my Linux machines failed, I took the opportunity to migrate from RAID5 to a 6-disk software RAID6 array. At the time of the migration I did not have all 6 drives - more specifically the fourth and fifth (slots 3 and 4) drives were already in use in the originating array, so I created the RAID6 array with a couple of missing devices. I now need to add those drives in those empty slots. Using mdadm --add does result in a proper RAID6 configuration, with one glitch - the new drives are placed in new slots, which results in this /proc/mdstat snippet: ... md0 : active raid6 sde1[7] sdd1[6] sda1[0] sdf1[5] sdc1[2] sdb1[1] 25185536 blocks super 1.0 level 6, 64k chunk, algorithm 2 [6/6] [UUUUUU] ... mdadm -E verifies that the actual slot numbers in the device superblocks are correct, yet the numbers shown in /proc/mdstat are still weird. I would like to fix this glitch, both to satisfy my inner perfectionist and to avoid any potential sources of future confusion in a crisis. Is there a way to specify which slot a new device should occupy in a RAID array? UPDATE: I have verified that the slot number persists in the component device superblock. For the version 1.0 superblocks that I am using that would be the dev_number field as defined in include/linux/raid/md_p.h of the Linux kernel source. I am now considering direct modification of said field to change the slot number - I don't suppose there is some standard way to manipulate the RAID superblock?

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  • Software RAID 1 Configuration

    - by Corve
    I have created a software RAID 1 quite some while ago and it always seemed to work for me. However I am not completely sure that I have configured everything right and do not have the experience to check so I would be very grateful for some advice or just verification that all seems right so far. I am using Linux Fedora 20 (32 bit with plans to upgrade to 64bit) The RAID 1 should consist of two 1TB SATA hard drives. This is the output of mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Creation Time : Sun Jan 29 11:25:18 2012 Raid Level : raid1 Array Size : 976761424 (931.51 GiB 1000.20 GB) Used Dev Size : 976761424 (931.51 GiB 1000.20 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Sat Jun 7 10:38:09 2014 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : argo:0 (local to host argo) UUID : 1596d0a1:5806e590:c56d0b27:765e3220 Events : 996387 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 0 1 active sync /dev/sda The RAID is mounted successfully: friedrich@argo:~ ? sudo mount -l | grep md0 /dev/md0 on /mnt/raid type ext4 (rw,relatime,data=ordered) Basically my question are: Why do I only have 1 active device? What does the State removed at bottom mean? Also I noticed some strange error messages that I see on the console on system start and shutdown and always repeating in the background when I switch with Ctrl + Alt + F2: ... ata2: irq_stat 0x00000040 connection status changed ata2: SError: { CommWake DevExch } ata2: COMRESET failed (errno=-32) ata2: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen ata2: irq_stat 0x00000040 connection status changed ata2: SError: { CommWake DevExch } ata2: exception Emask 0x10 SAct 0x0 SErr 0x4040000 action 0xe frozen ... Are these errors related to the RAID? Something seems wrong with the SATA devices.. All together the system works (I can read and write to the mounted raid) but I always had these strange errors on startup shutdown (probably always in the background). Thx for your help

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  • ANTS Performance Profiler 7.0 has been released!

    - by Michaela Murray
    Please join me in welcoming ANTS Performance Profiler 7 to the world of .NET. ANTS Performance Profiler is a .NET code profiling tool. It lets you identify performance bottlenecks within minutes and therefore enables you to optimize your application performance. Version 7.0 includes integrated decompilation: when profiling methods and assemblies with no source code file, you can generate source code right from the profiler interface. You can then browse and navigate this automatically generated source as if it was your own. If you have an assembly's PDB file but no source, integrated decompilation even lets you view line-level timings for each method, pinpointing the exact cause of performance bottlenecks. Integrated decompilation is powered by .NET Reflector, but you don't need Reflector installed to use the functionality. Watch this video to see it in action. Also new in ANTS Performance Profiler 7.0: · Full support for SharePoint 2010 - No need to manually configure profiling for the latest version of SharePoint · Full support for IIS Express · Azure and Amazon EC2 support, enabling you to profile in the cloud Please click here, for more details about the ANTS Performance Profiler 7.0.

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  • RAM caching causes severe performance drops

    - by B T
    I have read plenty of threads on memory caching and the standard response of "large cache is good, it shouldn't effect performance", "the kernel knows best". I have recently upgraded from 12.04 to 12.10 and changed from VirtualBox to VMware Workstation and the performance differences are severe (I suspect it is because of the latter). When I am running my virtual machine the system load monitor graph shows less than 50% memory usage generally. System load indicator is showing me that the rest of my RAM is used in the cache all the time. Plain and simple this is the comparison: BEFORE Cache was very sparingly used, pretty much none of my memory usage was the cache Swappiness was 0 (caused my memory to be used first, then swap only if needed) Performance was quite good and logical RAM was used fully first, caching was minimal. I could run enough software to utilize my full 4GB of RAM without any performance degradation whatsoever Swap space was then used as needed which was obviously slower (I am on a HDD) but was still usable when the current program was loaded into memory AFTER Cache is used to fill the full 4GB as soon as my virtual machine is run Swappiness is 0 (same behaviour as before but cache uses full memory straight away) Performance is terrible and unusable while running Ubuntu software Basic things like changing windows takes 2 minutes + Changing screens happens frame by frame over sometimes up to 5 minutes Cannot run an IDE and VM like I could with ease before So basically, any suggestions on how to take my performance back to how it was before while keeping my current setup? My suspicion is VMWare is the problem, but how do I see what is tied to the use of the cache? Surely there is a way to control this behaviour in software as polished as VMware? Thanks EDIT: Could also be important to note that the behaviour differs depending on whether VMware is open or closed. If VMware is open, then the ram will lock at like 50% and 50% cache and go into the complete lock up mentioned above. Contrastingly, if VMware is closed (after being open), then the RAM will continue to rise as it needs / cache will stay as the complete remaining memory and there is no noticeable performance degradation.

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  • Do software developers know what engineers actually do?

    - by lorin
    Software development is often contrasted with the traditional branches of engineering, most commonly civil or mechanical engineering. For example: "Software development isn't like engineering, it's like craftsmanship!" "Software development isn't like engineering, but it should be!" Do software developers understand what it is that engineers do and how they do it? At least, do they understand it well enough to be able to make an informed comparison with what software developers do?

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  • How to Tell a Hardware Problem From a Software Problem

    - by Chris Hoffman
    Your computer seems to be malfunctioning — it’s slow, programs are crashing or Windows may be blue-screening. Is your computer’s hardware failing, or does it have a software problem that you can fix on your own? This can actually be a bit tricky to figure out. Hardware problems and software problems can lead to the same symptoms — for example, frequent blue screens of death may be caused by either software or hardware problems. Computer is Slow We’ve all heard the stories — someone’s computer slows down over time because they install too much software that runs at startup or it becomes infected with malware. The person concludes that their computer is slowing down because it’s old, so they replace it. But they’re wrong. If a computer is slowing down, it has a software problem that can be fixed. Hardware problems shouldn’t cause your computer to slow down. There are some rare exceptions to this — perhaps your CPU is overheating and it’s downclocking itself, running slower to stay cooler — but most slowness is caused by software issues. Blue Screens Modern versions of Windows are much more stable than older versions of Windows. When used with reliable hardware with well-programmed drivers, a typical Windows computer shouldn’t blue-screen at all. If you are encountering frequent blue screens of death, there’s a good chance your computer’s hardware is failing. Blue screens could also be caused by badly programmed hardware drivers, however. If you just installed or upgraded hardware drivers and blue screens start, try uninstalling the drivers or using system restore — there may be something wrong with the drivers. If you haven’t done anything with your drivers recently and blue screens start, there’s a very good chance you have a hardware problem. Computer Won’t Boot If your computer won’t boot, you could have either a software problem or a hardware problem. Is Windows attempting to boot and failing part-way through the boot process, or does the computer no longer recognize its hard drive or not power on at all? Consult our guide to troubleshooting boot problems for more information. When Hardware Starts to Fail… Here are some common components that can fail and the problems their failures may cause: Hard Drive: If your hard drive starts failing, files on your hard drive may become corrupted. You may see long delays when you attempt to access files or save to the hard drive. Windows may stop booting entirely. CPU: A failing CPU may result in your computer not booting at all. If the CPU is overheating, your computer may blue-screen when it’s under load — for example, when you’re playing a demanding game or encoding video. RAM: Applications write data to your RAM and use it for short-term storage. If your RAM starts failing, an application may write data to part of the RAM, then later read it back and get an incorrect value. This can result in application crashes, blue screens, and file corruption. Graphics Card: Graphics card problems may result in graphical errors while rendering 3D content or even just while displaying your desktop. If the graphics card is overheating, it may crash your graphics driver or cause your computer to freeze while under load — for example, when playing demanding 3D games. Fans: If any of the fans fail in your computer, components may overheat and you may see the above CPU or graphics card problems. Your computer may also shut itself down abruptly so it doesn’t overheat any further and damage itself. Motherboard: Motherboard problems can be extremely tough to diagnose. You may see occasional blue screens or similar problems. Power Supply: A malfunctioning power supply is also tough to diagnose — it may deliver too much power to a component, damaging it and causing it to malfunction. If the power supply dies completely, your computer won’t power on and nothing will happen when you press the power button. Other common problems — for example, a computer slowing down — are likely to be software problems. It’s also possible that software problems can cause many of the above symptoms — malware that hooks deep into the Windows kernel can cause your computer to blue-screen, for example. The Only Way to Know For Sure We’ve tried to give you some idea of the difference between common software problems and hardware problems with the above examples. But it’s often tough to know for sure, and troubleshooting is usually a trial-and-error process. This is especially true if you have an intermittent problem, such as your computer blue-screening a few times a week. You can try scanning your computer for malware and running System Restore to restore your computer’s system software back to its previous working state, but these aren’t  guaranteed ways to fix software problems. The best way to determine whether the problem you have is a software or hardware one is to bite the bullet and restore your computer’s software back to its default state. That means reinstalling Windows or using the Refresh or reset feature on Windows 8. See whether the problem still persists after you restore its operating system to its default state. If you still see the same problem – for example, if your computer is blue-screening and continues to blue-screen after reinstalling Windows — you know you have a hardware problem and need to have your computer fixed or replaced. If the computer crashes or freezes while reinstalling Windows, you definitely have a hardware problem. Even this isn’t a completely perfect method — for example, you may reinstall Windows and install the same hardware drivers afterwards. If the hardware drivers are badly programmed, the blue-screens may continue. Blue screens of death aren’t as common on Windows these days — if you’re encountering them frequently, you likely have a hardware problem. Most blue screens you encounter will likely be caused by hardware issues. On the other hand, other common complaints like “my computer has slowed down” are easily fixable software problems. When in doubt, back up your files and reinstall Windows. Image Credit: Anders Sandberg on Flickr, comedy_nose on Flickr     

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  • TestRail 1.3 Test Management Software released

    Gurock Software just announced version 1.3 of its test management software TestRail. TestRail is a web-based test case management software that helps software development teams and QA departments to efficiently manage, track and organize their software testing efforts.

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  • Understanding Software Development Process

    Software development means, creating software to fulfill the specific needs of the customers. Depending upon their requirements, the software outsourcing firms develop customized software solutions. The client requirement can be an open source software or program for personal use.

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  • C# performance analysis- how to count CPU cycles?

    - by Lirik
    Is this a valid way to do performance analysis? I want to get nanosecond accuracy and determine the performance of typecasting: class PerformanceTest { static double last = 0.0; static List<object> numericGenericData = new List<object>(); static List<double> numericTypedData = new List<double>(); static void Main(string[] args) { double totalWithCasting = 0.0; double totalWithoutCasting = 0.0; for (double d = 0.0; d < 1000000.0; ++d) { numericGenericData.Add(d); numericTypedData.Add(d); } Stopwatch stopwatch = new Stopwatch(); for (int i = 0; i < 10; ++i) { stopwatch.Start(); testWithTypecasting(); stopwatch.Stop(); totalWithCasting += stopwatch.ElapsedTicks; stopwatch.Start(); testWithoutTypeCasting(); stopwatch.Stop(); totalWithoutCasting += stopwatch.ElapsedTicks; } Console.WriteLine("Avg with typecasting = {0}", (totalWithCasting/10)); Console.WriteLine("Avg without typecasting = {0}", (totalWithoutCasting/10)); Console.ReadKey(); } static void testWithTypecasting() { foreach (object o in numericGenericData) { last = ((double)o*(double)o)/200; } } static void testWithoutTypeCasting() { foreach (double d in numericTypedData) { last = (d * d)/200; } } } The output is: Avg with typecasting = 468872.3 Avg without typecasting = 501157.9 I'm a little suspicious... it looks like there is nearly no impact on the performance. Is casting really that cheap?

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  • Poor Ruby on Rails performance when using nested :include

    - by Jeremiah Peschka
    I have three models that look something like this: class Bucket < ActiveRecord::Base has_many :entries end class Entry < ActiveRecord::Base belongs_to :submission belongs_to :bucket end class Submission < ActiveRecord::Base has_many :entries belongs_to :user end class User < ActiveRecord::Base has_many :submissions end When I retrieve a collection of entries doing something like: @entries = Entry.find(:all, :conditions => ['entries.bucket_id = ?', @bucket], :include => :submission) The performance is pretty quick although I get a large number of extra queries because the view uses the Submission.user object. However, if I add the user to the :include statement, the performance becomes terrible and it takes over a minute to return a total of 50 entries and submissions spread across 5 users. When I run the associated SQL commands, they complete in well under a second. @entries = Entry.find(:all, :conditions => ['entries.bucket_id = ?', @bucket], :include => {:submission => :user}) Why would this second command have such terrible performance compared to the first?

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  • best way to set up a VM for development (regarding performance)

    - by raticulin
    I am trying to set up a clean vm I will use in many of my devs. Hopefully I will use it many times and for a long time, so I want to get it right and set it up so performance is as good as possible. I have searched for a list of things to do, but strangely found only older posts, and none here. My requirements are: My host is Vista 32b, and guest is Windows2008 64b, using Vmware Workstation. The VM should also be able to run on a Vmware ESX I cannot move to other products (VirtualBox etc), but info about performance of each one is welcomed for reference. Anyway I guess most advices would apply to other OSs and other VM products. I need network connectivity to my LAN Guest will run many java processes, a DB and perform lots of file I/O What I have found so far is: HOWTO: Squeeze Every Last Drop of Performance Out of Your Virtual PCs: it's and old post, and about Virtual PC, but I guess most things still apply (and also apply to vmware). I guess it makes a difference to disable all unnecessary services, but the ones mentioned in 1 seem like too few, I specifically always disable Windows Search. Any other service I should disable?

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  • Rails performance tests "rake test:benchmark" and "rake test:profile" give me errors

    - by go minimal
    I'm trying to run a blank default performance test with Ruby 1.9 and Rails 2.3.5 and I just can't get it to work! What am I missing here??? rails testapp cd testapp script/generate scaffold User name:string rake db:migrate rake test:benchmark - /usr/local/bin/ruby19 -I"lib:test" "/usr/local/lib/ruby19/gems/1.9.1/gems/rake-0.8.7/lib/rake/rake_test_loader.rb" "test/performance/browsing_test.rb" -- --benchmark Loaded suite /usr/local/lib/ruby19/gems/1.9.1/gems/rake-0.8.7/lib/rake/rake_test_loader Started /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:105:in `rescue in const_missing': uninitialized constant BrowsingTest::STARTED (NameError) from /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:94:in `const_missing' from /usr/local/lib/ruby19/gems/1.9.1/gems/activesupport-2.3.5/lib/active_support/testing/performance.rb:38:in `run' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:415:in `block (2 levels) in run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:409:in `each' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:409:in `block in run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:408:in `each' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:408:in `run_test_suites' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:388:in `run' from /usr/local/lib/ruby19/1.9.1/minitest/unit.rb:329:in `block in autorun' rake aborted! Command failed with status (1): [/usr/local/bin/ruby19 -I"lib:test" "/usr/l...]

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  • Java Performance measurement

    - by portoalet
    Hi, I am doing some Java performance comparison between my classes, and wondering if there is some sort of Java Performance Framework to make writing performance measurement code easier? I.e, what I am doing now is trying to measure what effect does it have having a method as "synchronized" as in PseudoRandomUsingSynch.nextInt() compared to using an AtomicInteger as my "synchronizer". So I am trying to measure how long it takes to generate random integers using 3 threads accessing a synchronized method looping for say 10000 times. I am sure there is a much better way doing this. Can you please enlighten me? :) public static void main( String [] args ) throws InterruptedException, ExecutionException { PseudoRandomUsingSynch rand1 = new PseudoRandomUsingSynch((int)System.currentTimeMillis()); int n = 3; ExecutorService execService = Executors.newFixedThreadPool(n); long timeBefore = System.currentTimeMillis(); for(int idx=0; idx<100000; ++idx) { Future<Integer> future = execService.submit(rand1); Future<Integer> future1 = execService.submit(rand1); Future<Integer> future2 = execService.submit(rand1); int random1 = future.get(); int random2 = future1.get(); int random3 = future2.get(); } long timeAfter = System.currentTimeMillis(); long elapsed = timeAfter - timeBefore; out.println("elapsed:" + elapsed); } the class public class PseudoRandomUsingSynch implements Callable<Integer> { private int seed; public PseudoRandomUsingSynch(int s) { seed = s; } public synchronized int nextInt(int n) { byte [] s = DonsUtil.intToByteArray(seed); SecureRandom secureRandom = new SecureRandom(s); return ( secureRandom.nextInt() % n ); } @Override public Integer call() throws Exception { return nextInt((int)System.currentTimeMillis()); } } Regards

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  • Java performance issue

    - by Colby77
    Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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  • Need guidelines for optimizing WebGL performance by minimizing shader changes

    - by brainjam
    I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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  • Improving I/O performance in C++ programs[external merge sort]

    - by Ajay
    I am currently working on a project involving external merge-sort using replacement-selection and k-way merge. I have implemented the project in C++[runs on linux]. Its very simple and right now deals with only fixed sized records. For reading & writing I use (i/o)fstream classes. After executing the program for few iterations, I noticed that I/O read blocks for requests of size more than 4K(typical block size). Infact giving buffer sizes greater than 4K causes performance to decrease. The output operations does not seem to need buffering, linux seemed to take care of buffering output. So I issue a write(record) instead of maintaining special buffer of writes and then flushing them out at once using write(records[]). But the performance of the application does not seem to be great. How could I improve the performance? Should I maintain special I/O threads to take care of reading blocks or are there existing C++ classes providing this abstraction already?(Something like BufferedInputStream in java)

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  • JDBC programms running long time performance issue

    - by phyerbarte
    My program has an issue with Oracle query performance, I believe the SQL have good performance, because it returns quickly in SQLPlus. But when my program has been running for a long time, like 1 week, the SQL query (using JDBC) becomes slower (In my logs, the query time is much longer than when I originally started the program). When I restart my program, the query performance comes back to normal. I think it is could be something wrong with the way I use the preparedStatement, because the SQL I'm using does not use placeholders "?" at all. Just a complex select query. The query process is done by a util class. Here is the pertinent code building the query: public List<String[]> query(String sql, String[] args) { Connection conn = null; conn = openConnection(); conn.setAutocommit(true); .... PreparedStatement preStatm = null; ResultSet rs = null; ....//set preparedstatment arg code rs = preStatm.executeQuery(); .... finally{ //close rs //close prestatm //close connection } } In my case, the args is always null, so it just passes a query sql to this query method. Is that possible this way could slow down the DB query after program long time running? Or I should use statement instead, or just pass args with "?" in the SQL? How can I find out the root cause for my issue? Thanks.

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  • Essbase Analytics Link (EAL) - Performance of some operation of EAL could be improved by tuning of EAL Data Synchronization Server (DSS) parameters

    - by Ahmed Awan
    Generally, performance of some operation of EAL (Essbase Analytics Link) could be improved by tuning of EAL Data Synchronization Server (DSS) parameters. a. Expected that DSS machine will be 64-bit machine with 4-8 cores and 5-8 GB of RAM dedicated to DSS. b. To change DSS configuration - open EAL Configuration Tool on DSS machine.     ->Next:     and define: "Job Units" as <Number of Cores dedicated to DSS> * 1.5 "Max Memory Size" (if this is 64-bit machine) - ~1G for each Job Unit. If DSS machine is 32-bit - max memory size is 2600 MB. "Data Store Size" - depends on number of bridges and volume of HFM applications, but in most cases 50000 MB is enough. This volume should be available in defined "Data Store Dir" driver.   Continue with configuration and finish it. After that, DSS should be restarted to take new definitions.  

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  • Why is Python used for high-performance/scientific computing (but Ruby isn't)?

    - by Cyclops
    There's a quote from a PyCon 2011 talk that goes: At least in our shop (Argonne National Laboratory) we have three accepted languages for scientific computing. In this order they are C/C++, Fortran in all its dialects, and Python. You’ll notice the absolute and total lack of Ruby, Perl, Java. It was in the more general context of high-performance computing. Granted the quote is only from one shop, but another question about languages for HPC, also lists Python as one to learn (and not Ruby). Now, I can understand C/C++ and Fortran being used in that problem-space (and Perl/Java not being used). But I'm surprised that there would be a major difference in Python and Ruby use for HPC, given that they are fairly similar. (Note - I'm a fan of Python, but have nothing against Ruby). Is there some specific reason why the one language took off? Is it about the libraries available? Some specific language features? The community? Or maybe just historical contigency, and it could have gone the other way?

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  • Information about rendering, batches, the graphical card, performance etc. + XNA?

    - by Aidiakapi
    I know the title is a bit vague but it's hard to describe what I'm really looking for, but here goes. When it comes to CPU rendering, performance is mostly easy to estimate and straightforward, but when it comes to the GPU due to my lack of technical background information, I'm clueless. I'm using XNA so it'd be nice if theory could be related to that. So what I actually wanna know is, what happens when and where (CPU/GPU) when you do specific draw actions? What is a batch? What influence do effects, projections etc have? Is data persisted on the graphics card or is it transferred over every step? When there's talk about bandwidth, are you talking about a graphics card internal bandwidth, or the pipeline from CPU to GPU? Note: I'm not actually looking for information on how the drawing process happens, that's the GPU's business, I'm interested on all the overhead that precedes that. I'd like to understand what's going on when I do action X, to adapt my architectures and practices to that. Any articles (possibly with code examples), information, links, tutorials that give more insight in how to write better games are very much appreciated. Thanks :)

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