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  • How to implement a Linked List in Java?

    - by nbarraille
    Hello! I am trying to implement a simple HashTable in Java that uses a Linked List for collision resolution, which is pretty easy to do in C, but I don't know how to do it in Java, as you can't use pointers... First, I know that those structures are already implemented in Java, I'm not planning on using it, just training here... So I created an element, which is a string and a pointer to the next Element: public class Element{ private String s; private Element next; public Element(String s){ this.s = s; this.next = null; } public void setNext(Element e){ this.next = e; } public String getString(){ return this.s; } public Element getNext(){ return this.next; } @Override public String toString() { return "[" + s + "] => "; } } Of course, my HashTable has an array of Element to stock the data: public class CustomHashTable { private Element[] data; Here is my problem: For example I want to implement a method that adds an element AT THE END of the linked List (I know it would have been simpler and more efficient to insert the element at the beginning of the list, but again, this is only for training purposes). How do I do that without pointer? Here is my code (which could work if e was a pointer...): public void add(String s){ int index = hash(s) % data.length; System.out.println("Adding at index: " + index); Element e = this.data[index]; while(e != null){ e = e.getNext(); } e = new Element(s); } Thanks!

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  • Change Default Winform Icon Across Entire App

    - by Kyle Gagnet
    Can I change the default icon used on a Winform? Most of my forms have their icon property set to a custom icon. For the few forms that slip through the cracks, I don't want the generic "hey look, he made this in visual studio" icon. One solution is to tediously check every one of my forms to make sure they either have a custom icon set or have ShowIcon set to False. Another solution is to have every one of my forms inherit from a base class that sets a custom icon in the constructor. Aside from those solutions, what other options do I have? EDIT: I was hoping there would be a way to replace the source of the stock icon with my own. Is it in a resource file somewhere? Or is it embedded in a .NET dll that I can't (or really, really shouldn't) modify? BOUNTY EDIT: Is there a way to accomplish this without editing or writing a single line of code? I don't care how impractical, complicated, waste-of-time the solution is... I just want to know if it's possible. I need to satisfy my curiosity.

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  • BIOS upgrade lowers CPU temperature

    - by N.N.
    Setup I've got a system with an Asus P8Z68-V PRO motherboard and an Intel Core i7-2600K CPU running at stock speed (no overlocking) which I cool with a Noctua NH-U12P. On the heatsink I've got the two included fans connected via the included Low-Noise Adapters (L.N.A.) 1100 RPM, 16.9 dB(A). In the BIOS settings I've set the CPU and chassis fan profile to silent. Issue Yesterday I upgraded from BIOS version 0501 to 0606. After the upgrade I checked the temperatures in the BIOS monitor and was surprised to see that the CPU temperature was slightly ~30°C. Before the upgrade the CPU temperature was ~50°C with the same BIOS settings (see the following heading for details on temperatures). How can this be? It seems a bit odd that a BIOS upgrade can lower the CPU temperature by 20°C and it also seems odd that the CPU temperature is lower than the chassis temperature. Temperatures When I've checked temperatures the room temperature has been ~23°C. I haven't changed the placement of the computer nor the hardware or cooling setup between BIOS versions. BIOS version 0501 BIOS monitor: CPU: ~50°C Chassis: ~33°C I haven't got any temperature measures from lm-sensors or the like for version 0501 because I only discovered the issue after upgrading to version 0606 and the BIOS updater utility won't let me downgrade to version 0501 (it says "outdated image" when I try to load version 0501). BIOS version 0606 BIOS monitor: CPU: ~30°C Chassis: ~33°C lm-sensors in Ubuntu 11.04 Desktop 64-bit (sudo sensors after an uptime of 4 h 52 min and a load average of 0.22, 0.18, 0.15): coretemp-isa-0000 Adapter: ISA adapter Core 0: +32.0°C (high = +80.0°C, crit = +98.0°C) coretemp-isa-0001 Adapter: ISA adapter Core 1: +35.0°C (high = +80.0°C, crit = +98.0°C) coretemp-isa-0002 Adapter: ISA adapter Core 2: +29.0°C (high = +80.0°C, crit = +98.0°C) coretemp-isa-0003 Adapter: ISA adapter Core 3: +36.0°C (high = +80.0°C, crit = +98.0°C) The BIOS monitor temperatures was checked directly after the lm-sensors temperatures was checked. BIOS version 0706, 0801, 1101 and 3203 I get the same kind of temperatures both in the BIOS monitor and with lm-sensors in BIOS version 0706, 0801, 1101 and 3203 as in 0606. Information from Asus The 0606 changelog mentions nothing explicitly about CPU temperature (but item 3., as indicated by sidran32, might affect temperatures): P8Z68-V PRO 0606 BIOS with IRST 10.6.0.1002 Enable the support of Intel Rapid Storage Technology version 10.6.0.1002 Release Improve DRAM compatibility Improve System stability Improve compatibility with some Raid card model Increase IGD share memory size to 512MB However the following FAQ might give a hint: FAQs I find that the CPU temperature reading in BIOS is about 10~20 degrees centigrade hotter than the reading in OS. Is it normal? Page Tools Solution That is normal as BIOS does not send idle command to the CPU, making most of the power saving features useless. You should be getting similar reading if you disable EIST/C1E/CPU C3 Report/CPU C6 Report in BIOS.

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  • Automating video generation by adding an intro and a trailing video to the main video

    - by DevDewboy
    I have a video project I am trying to compile. Here is the overview: I have many videos which are 5 minute training sessions - Main video. The Intro Video will be a standard 5 second video that will have the Video title and Author. This will be concatenated to the main video. The Trailing Video will pretty much be a stock video that will be concatenated to the main video and have all the legaleze etc. The Intro Vid will smoothly fade into the main vid as well as when you get to end of the main video it will fade into the Trailing video nicely. The product is a new video with a Intro, Main & Trailer video all in one! The concept is really that simple. In fact I found an example of a person who has solved this and is doing exactly what I want. This solution is a Bash script that takes a config file that has the title, author, etc. and generates the Intro, the Ending and creates the resulting video with them concatenated. I am using Ubuntu 12.04 Server. I have been trying to take this as a sample and just running it with no luck because of incompatibility errors. I even attempted to convert it using .MP4 containers or .MKV. I am running into error after error or incompatibility issues. I went as far as changing out the ffmpeg binary using the 25 Oct 2013 version from http://ffmpeg.gusari.org/static/64bit/ which I like as I don't have to worry about rebuilding the binary. Almost successful but again I have some error which I cannot solve. I know part of the problem is the fact that video production, codecs, formats is a completely new field for me so I am attempting to work through this new territory. Perhaps an expert here has something similar that I can use as a guideline that uses MP4 or h.264 format. Or take the solution above from the URL and make it work with a more up-to-date version of ffmpeg. I will include the script and its parameter file and the output (abbreviated because of limitation) below. Basically as the script stands right now, when run I get the error [matroska,webm @ 0x27bbee0] Read error. This error is return from the 'reasembleVideo' routine from the first ffmpeg command. The following is the Parameter File: #!/bin/bash INPUTFILE="ssh_main.mp4" LOGO="logo.png" LOGOLENGTH="1" SPEAKER="Jason" TITLE="Basic SSH Video" DATE="October 28, 2013" SCENESTART="00:00:01" SCENEDURATION="00:00:09" OUTPUTFILE="ssh_basic_1" } The following is the script I am running. The ${OUTPUTFILE} being used is a small 2 minute video I create in screen-o-matic in MP4 format. Script on PasteBin (too long for Super User post)

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  • Uninstall php and nginx or fix setup

    - by jreed121
    First off, I'm a huge linux noob - sorry... I'm trying to setup nginx with php-fpm on debian and I'm pretty sure that I've completely screwed it up. nginx seems to be running fine because I can it it from a web browser and it load the stock "Welcome to nginx!" page. I'm not so sure about php-fpm though. When I try something like # restart php-fpm I get: bash: restart: command not found First off php-fpm some how got installed as php5-fpm when I do root@server:/etc/init.d# ls, which seems to contradict every tutorial and help doc I've read (supposed to be 'php-fpm'). I can restart it with this: service php5-fpm restart And just enter the package name 'php5-fpm' I get this: root@server:~# php5-fpm [17-Nov-2012 23:15:36] NOTICE: PHP message: PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20100525/suhosin.so' - /usr/lib/php5/20100525/suhosin.so: cannot open shared object file: No such file or directory in Unknown on line 0 [17-Nov-2012 23:15:36] ERROR: An another FPM instance seems to already listen on /var/run/php5-fpm.sock [17-Nov-2012 23:15:36] ERROR: FPM initialization failed The root for nginx is /usr/share/nginx/html, when I try to navigate to a .php file in there with my web browser, it tries to download the file instead of interpret it. I would like this folder to be in my user's home directory ie: /home/administrator/www or /home/nginx/www. I know in order to do this I need to modify nginx.conf, but I find that configuration file difficult to understand. I suppose the fact that my .php scripts aren't being handled is my bigger problem anyways. When I try to see what running on port 9000 (php-fpm default port) with lsof -i :9000 it returns nothing - I guess indicating that it isn't listening. then I head over to vim /etc/php5/fpm/php-fpm.conf and there is no where to designate a port number. So should I just uninstall everything and start from scratch? If so, how do I clean it all up? Any suggestions for a tutorial once I'm ready to try again? Should I attempt to troubleshoot this mess? If so where should I start? Sorry guys, I'm feeling pretty stupid and lost right now. I'm not sure what my next steps are in trying to resolve this issue are. I realize that this is a horrible question for this type of Q&A site, but I'd really appreciate any guidance.

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  • Best Processor for MediaSmart Server?

    - by Kent Boogaart
    I'm trying to figure out what the best possible processor is that I can stick in my HP MediaSmart server. I'm clueless when it comes to correlating CPUs to motherboards. I suspect it's the socket type I care about, but I worry that there's more to it. CPU-Z gives me (excerpt): Processors Information ------------------------------------------------------------------------- Processor 1 ID = 0 Number of cores 1 (max 1) Number of threads 1 (max 1) Name AMD Sempron LE-1150 Codename Sparta Specification AMD Sempron(tm) Processor LE-1150 Package Socket AM2 (940) CPUID F.F.1 Extended CPUID F.7F Brand ID 1 Core Stepping DH-G1 Technology 65 nm Core Speed 1000.0 MHz Multiplier x FSB 5.0 x 200.0 MHz HT Link speed 800.0 MHz Stock frequency 2000 MHz Instructions sets MMX (+), 3DNow! (+), SSE, SSE2, SSE3, x86-64 L1 Data cache 64 KBytes, 2-way set associative, 64-byte line size L1 Instruction cache 64 KBytes, 2-way set associative, 64-byte line size L2 cache 256 KBytes, 16-way set associative, 64-byte line size FID/VID Control yes Max FID 10.0x Max VID 1.350 V P-State FID 0x2 - VID 0x12 (5.0x - 1.100 V) P-State FID 0xA - VID 0x0C (9.0x - 1.250 V) P-State FID 0xC - VID 0x0A (10.0x - 1.300 V) K8 Thermal sensor yes K8 Revision ID 6.0 Attached device PCI device at bus 0, device 24, function 0 Attached device PCI device at bus 0, device 24, function 1 Attached device PCI device at bus 0, device 24, function 2 Attached device PCI device at bus 0, device 24, function 3 Chipset ------------------------------------------------------------------------- Northbridge SiS 761GX rev. 02 Southbridge SiS 966 rev. 59 Graphic Interface AGP AGP Revision 3.0 AGP Transfer Rate 8x AGP SBA supported, enabled Memory Type DDR2 Memory Size 2048 MBytes Channels Single Memory Frequency 200.0 MHz (CPU/5) CAS# latency (CL) 5.0 RAS# to CAS# delay (tRCD) 5 RAS# Precharge (tRP) 5 Cycle Time (tRAS) 15 Bank Cycle Time (tRC) 21 Command Rate (CR) 1T DMI ------------------------------------------------------------------------- DMI BIOS vendor Phoenix Technologies, LTD version R03 date 05/08/2008 DMI System Information manufacturer HP product MediaSmart Server version unknown serial CN68330DGH UUID A482007B-B0CC7593-DD11736A-407B7067 DMI Baseboard vendor Wistron model SJD4 revision A.0 serial unknown DMI System Enclosure manufacturer HP chassis type Desktop chassis serial unknown DMI Processor manufacturer AMD model AMD Sempron(tm) Processor LE-1150 clock speed 2000.0 MHz FSB speed 200.0 MHz multiplier 10.0x DMI Memory Controller correction 64-bit ECC Max module size 4096 MBytes DMI Memory Module designation A0 size 2048 MBytes (double bank) DMI Memory Module designation A1 DMI Memory Module designation A2 DMI Memory Module designation A3 DMI Port Connector designation PS/2 Mouse (internal) port type Mouse Port connector PS/2 connector PS/2 DMI Port Connector designation USB0 (external) port type USB DMI Physical Memory Array location Motherboard usage System Memory correction None max capacity 16384 MBytes max# of devices 4 DMI Memory Device designation A0 format DIMM type unknown total width 64 bits data width 64 bits size 2048 MBytes DMI Memory Device designation A1 format DIMM type unknown total width 64 bits data width 64 bits DMI Memory Device designation A2 format DIMM type unknown total width 64 bits data width 64 bits DMI Memory Device designation A3 format DIMM type unknown total width 64 bits data width 64 bits How do I figure out what options I have for an upgrade?

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  • Very poor read performance compared to write performance on md(raid1) / crypt(luks) / lvm

    - by Android5360
    I'm experiencing very poor read performance over raid1/crypt/lvm. In the same time, write speeds are about 2x+ faster on the same setup. On another raid1 setup on the same machine I get normal read speeds (maybe because I'm not using cryptsetup). OS related disks: sda + sdb. I have raid1 configuration with two disks, both are in place. I'm using LVM over the RAID. No encryption. Both disks are WD Green, 5400 rpm. IO test results on this raid1: dd if=/dev/zero of=/tmp/output.img3 bs=8k count=256k conv=fsync - 2147483648 bytes (2.1 GB) copied, 22.3392 s, 96.1 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=/tmp/output.img3 of=/dev/null bs=8k - 2147483648 bytes (2.1 GB) copied, 15.9 s, 135 MB/s And here is the problematic setup (on the same machine). Currently I have only one sdc (WD Green, 5400rpm) configured in software raid1 + crypt (luks, serpent-xts-plain) + lvm. Tomorrow I will attach another disk (sdd) to complete this two-disk raid1 setup. IO tests results on this raid1: dd if=/dev/zero of=output.img3 bs=8k count=256k conv=fsync 2147483648 bytes (2.1 GB) copied, 17.7235 s, 121 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=output.img3 of=/dev/null bs=8k 2147483648 bytes (2.1 GB) copied, 36.2454 s, 59.2 MB/s We can see that the read performance is very very bad (59MB/s compared to 135MB/s when using no encryption). Nothing is using the disks during benchmark. I can confirm this because I checked with iostat and dstat. Details on the hardware: disks: all are WD green, 5400rpm, 64mb cache. cpu: FX-8350 at stock speed ram: 4x4GB at 1066Mhz. Details on the software: OS: Debian Wheezy 7, amd64 mdadm: v3.2.5 - 18th May 2012 LVM version: 2.02.95(2) (2012-03-06) LVM Library version: 1.02.74 (2012-03-06) LVM Driver version: 4.22.0 cryptsetup: 1.4.3 Here is how I configured the slow raid1+crypt+lvm setup: parted /dev/sdc mklabel gpt type: ext4 start: 2048s end: -1 Now the raid, crypt and the lvm configuration: mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdc cryptsetup --cipher serpent-xts-plain luksFormat /dev/md1 cryptsetup luksOpen /dev/md1 md1_crypt vgcreate vg_sql /dev/mapper/md1_crypt lvcreate -l 100%VG vg_sql -n lv_sql mkfs.ext4 /dev/mapper/vg_sql-lv-sql mount /dev/mapper/vg_sql-lv_sql /sql So guys, can you help me identify the reason and fix it? It has to be something with the cryptsetup as there is no such read slowdown on the other setup (sda+sdb) where no encryption is present. But I have no idea what to do. Thanks!

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  • Postmaster uses excessive CPU and Disk Writes

    - by wolfcastle
    using PostgreSQL 9.1.2 I'm seeing excessive CPU usage and large amounts of writes to disk from postmaster tasks. This happens even while my application is doing almost nothing (10s of inserts per MINUTE). There are a reasonable number of connections open however. I've been trying to determine what in my application is causing this. I'm pretty newb with postgresql, and haven't gotten anywhere so far. I've turned on some logging options in my config file, and looked at connections in the pg_stat_activity table, but they are all idle. Yet each connection consumes ~ 50% CPU, and is writing ~15M/s to disk (reading nothing). I'm basically using the stock postgresql.conf with very little tweaks. I'd appreciate any advice or pointers on what I can do to track this down. Here is a sample of what top/iotop is showing me: Cpu(s): 18.9%us, 14.4%sy, 0.0%ni, 53.4%id, 11.8%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 32865916k total, 7263720k used, 25602196k free, 575608k buffers Swap: 16777208k total, 0k used, 16777208k free, 4464212k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 17057 postgres 20 0 236m 33m 13m R 45.0 0.1 73:48.78 postmaster 17188 postgres 20 0 219m 15m 11m R 42.3 0.0 61:45.57 postmaster 17963 postgres 20 0 219m 16m 11m R 42.3 0.1 27:15.01 postmaster 17084 postgres 20 0 219m 15m 11m S 41.7 0.0 63:13.64 postmaster 17964 postgres 20 0 219m 17m 12m R 41.7 0.1 27:23.28 postmaster 18688 postgres 20 0 219m 15m 11m R 41.3 0.0 63:46.81 postmaster 17088 postgres 20 0 226m 24m 12m R 41.0 0.1 64:39.63 postmaster 24767 postgres 20 0 219m 17m 12m R 41.0 0.1 24:39.24 postmaster 18660 postgres 20 0 219m 14m 9.9m S 40.7 0.0 60:51.52 postmaster 18664 postgres 20 0 218m 15m 11m S 40.7 0.0 61:39.61 postmaster 17962 postgres 20 0 222m 19m 11m S 40.3 0.1 11:48.79 postmaster 18671 postgres 20 0 219m 14m 9m S 39.4 0.0 60:53.21 postmaster 26168 postgres 20 0 219m 15m 10m S 38.4 0.0 59:04.55 postmaster Total DISK READ: 0.00 B/s | Total DISK WRITE: 195.97 M/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 17962 be/4 postgres 0.00 B/s 14.83 M/s 0.00 % 0.25 % postgres: aggw aggw [local] idle 17084 be/4 postgres 0.00 B/s 15.53 M/s 0.00 % 0.24 % postgres: aggw aggw [local] idle 17963 be/4 postgres 0.00 B/s 15.00 M/s 0.00 % 0.24 % postgres: aggw aggw [local] idle 17188 be/4 postgres 0.00 B/s 14.80 M/s 0.00 % 0.24 % postgres: aggw aggw [local] idle 17964 be/4 postgres 0.00 B/s 15.50 M/s 0.00 % 0.24 % postgres: aggw aggw [local] idle 18664 be/4 postgres 0.00 B/s 15.13 M/s 0.00 % 0.23 % postgres: aggw aggw [local] idle 17088 be/4 postgres 0.00 B/s 14.71 M/s 0.00 % 0.13 % postgres: aggw aggw [local] idle 18688 be/4 postgres 0.00 B/s 14.72 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle 24767 be/4 postgres 0.00 B/s 14.93 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle 18671 be/4 postgres 0.00 B/s 16.14 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle 17057 be/4 postgres 0.00 B/s 13.58 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle 26168 be/4 postgres 0.00 B/s 15.50 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle 18660 be/4 postgres 0.00 B/s 15.85 M/s 0.00 % 0.00 % postgres: aggw aggw [local] idle

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  • Skyrim: Heavy Performance Issues after a couple of location changes

    - by Derija
    Okay, I've tried different solutions: ENB Series, removing certain mods, checking my FPS Rate, monitoring my resources, .ini tweaks. It's all just fine, I don't see what I'm missing. A couple of days ago, I bought Skyrim. Before I bought the game, I admit I had a pirated copy because my girlfriend actually wanted to buy me the game as a present, then said she didn't have enough money. Sick of waiting, I decided to buy the game by myself. The ridiculous part is, it worked better cracked than it does now uncracked. As the title suggests, after entering and leaving houses a couple of times, my performance obviously drops extremely. My build is just fine, Intel i5 quad core processor, NVIDIA GTX 560 Ti from Gigabyte, actually stock-OC, but manually downclocked to usual settings using appropriate Gigabyte software. This fixed the CTD issues I had before with both Skyrim and BF3. I have 4GB RAM. A website about Game Tweaks suggested that my HDD may be too slow. A screenshot of a Windows Performance Index sample with the subscription "This is likely to cause issues" showed the HDD with a performance index of 5.9, the exact same mine has, so I was playing with the thought to purchase an SSD instead, load games onto it that really need it like Skyrim, and hope it'd do the trick. Unfortunately, SSDs are likewise expensive, compared to "normal" HDDs... I'm really getting desperate about it. My save is gone because the patches made it impossible to load saves of the unpatched version and I already saved more than 80 times despite being only level 8, just because every time I interact with a door leading me to another location I'm scared the game will drop again. I can't even play for 30 mins straight anymore, it's just no fun at all. I've researched for a couple of days before I decided to post my question here. Any help is appreciated, I don't want to regret having bought the game... Since it actually is the best game I've played possibly for ever. Sincerely. P.S.: I don't think it's necessary to say, but still, of course I'm playing on PC. P.P.S.: After monitoring both my PC resources including CPU usage and HDD usage as well as the GPU usage, I don't see any changes even after the said event. P.P.P.S.: Original question posted here where I've been advised to ask here.

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  • Suspend only works once after full power cycle with ASUS P7P55D-E Pro

    - by John Chadwick
    This one is strange. I can't seem to get suspend working more than once per power cycle. When I say "power cycle," I mean the only way to get one proper suspend is to cut power from the power supply and boot back up cold. After the proper suspend, I get a failed suspend, and after all reboots or cold boots until power is cut, suspends fail. I'm using an ASUS P7P55D-E Pro with a Sandy Bridge Core i7, running on Ubuntu Precise repositories and UEFI. I'm running Nouveau from repository (And Gallium3d compiled from git, but that does not come into this since I can avoid OpenGL and it still happens the same way) with a GTX 285 (nv50.) I had to build a custom kernel (3.3) in order for ACPI 5.0 to be supported and make suspend work at all. I compiled it using the latest Ubuntu kernel's config file with the additional entries set to the default options. All packages are up to date. I know these are relatively exotic settings, but I'm hoping maybe I can get some help anyways. The behavior when suspend fails is strange. Upon a proper suspend, all fans turn off and the only led left on, the power led, is blinking. Upon a failed suspend, 1. USB power remains. 2. The power led stays on solid. 3. All fans seem to still be on. 4. I can hear what I believe is the primary harddrive shutting off. 5. Despite USB power remaining, the USB powered keyboard does not respond to anything, and the indicator leds on it shut off. Pressing the power button does nothing, and of course I have not to date found a way to wake it up. When trouble shooting the first round of issues I got with suspend not too long ago, I ended up building a list of modules to disable upon sleeping. Here's my config file for them: In /etc/pm/config.d/01modules: SUSPEND_MODULES="uhci_hd ehci_hd button" All of my other pm configuration files are stock. In case it's any help, here are my relevant BIOS settings. Thanks.

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  • Why is my new Phenom II 965 BE not significantly faster than my old Athlon 64 X2 4600+?

    - by Software Monkey
    I recently rebuilt my 5 year old computer. I upgraded all core components, in particular from an Athlon 64 X2 4600+ at 2.4 GHz with DDR2 800 to a Phenom II 965 BE (quad core) at 3.6 GHz with DDR3 1333 (actually 1600, but testing consistently detected memory errors at 1600). The motherboard is also much newer and better. The HDD's (x3), DVD writer and card reader are the same. The BIOS memory config is auto-everything except the base timing which I overrode to 1T instead of 2T. The BIOS CPU multiplier is slightly over-clocked to 3.6 GHz from the stock 3.4 GHz. I noticed compiling Java is slower than I expected. As it happens I have some (single-threaded) Java pattern-matching code which is CPU and memory bound and for which I have performance numbers recorded on a number of hardware platforms, including my old system. So I did a test run on the new equipment and was stunned to find that the numbers are only slightly better than my old system, about 25%. The data set it is operating on is a 148,975 character array, which should easily fit in caches, but in any event the new CPU has larger caches all around. The system was, of course, otherwise idle for the test and the test run is a timed 10 seconds to eliminate scheduling anomalies. A long while ago, when I upgraded only memory from DD2 667 to DDR2 800 there was no change in performance of this test, which subjectively supports that the test cycle does not need to (significantly) access main memory, but yes it is creating and garbage collecting a large number of objects in the process of this test (low millions of matches are found for the pattern set). I am about 99.999% certain the code hasn't changed since I last ran it on 2009-03-17 - but I can't easily retest the old hardware, because it is currently in pieces on my work-bench waiting to be built into a new computer for my kids. Note that Windows (XP) reports a CPU speed of 795 MHz unless I have some thing running. With stuff running it seems to jump all over the place each time I use ALT-Pause to display the system properties, everywhere from 795 MHz to 3.4 Ghz. So why might my shiny new hardware under-performing so badly? EDIT: The old memory was Mushkin DDR2 800 with timings set for auto which should have been 5-5-5-12. The new memory is Corsair DDR3 1600, running at 1333 with timings also auto which are 9-9-9-21. In both cases they are a paired set of dual channel DIMMs. I was waiting to ensure my system was stable before tweaking with memory timings.

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  • Ubuntu with KVM guest VM and broken bridges

    - by MadPsy
    I have an Ubuntu box with a KVM guest VM running. They use bridging so the guest VM attaches to the physical network of its host. The guest VM has 2 NICs in 2 different bridges. First NIC of the VM is tap5 and is in bridge br0 br0 8000.46720f5c572e no eth0.500 tap5 Second NIC of the VM is tap2 and is in bridge br100 br100 8000.76ad2fc96661 no eth0.100 eth0.101 eth0.103 eth0.104 eth0.105 tap2 On the host, br0 has an IP and br100 does not 21: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 46:72:0f:5c:57:2e brd ff:ff:ff:ff:ff:ff inet 192.168.100.4/24 brd 192.168.10.255 scope global br0 inet6 fe80::d6ae:52ff:febe:777/64 scope link valid_lft forever preferred_lft forever On the guest, its eth0 and eth1 interfaces both have IP addresses 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:3e:61:fb:7a:da brd ff:ff:ff:ff:ff:ff inet 192.168.100.6/24 brd 192.168.100.255 scope global eth0 inet6 fe80::23e:61ff:fefb:7ada/64 scope link valid_lft forever preferred_lft forever 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:3e:61:fb:7a:ea brd ff:ff:ff:ff:ff:ff inet 172.16.50.129/25 brd 172.16.50.255 scope global eth1 inet6 fe80::23e:61ff:fefb:7aea/64 scope link valid_lft forever preferred_lft forever On the guest VM, a tcpdump of its eth1 interface (tap2) shows traffic from its eth0 interface (tap5), as if the 2 bridges are themselves bridged. This means any interface on br100 is now bridged across to br0 - which is completely broken. root@chillispot:~# tcpdump -c 1 -n -v -i eth1 net 192.168.100.0/24 tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes 16:31:24.175583 IP (tos 0x0, ttl 64, id 48054, offset 0, flags [DF], proto TCP (6), length 148) 192.168.100.6.22 > 192.168.100.4.59505: Flags [P.], cksum 0x6c2b (correct), seq 1056321648:1056321744, ack 398642983, win 1700, options [nop,nop,TS val 197473436 ecr 200655363], length 96 What could be bridging the 2 bridges, except the guest VM (which is a stock Ubuntu install)? I am at a complete loss! Thanks.

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  • Anyone else experiencing high rates of Linux server crashes during a leap second day?

    - by Bron Gondwana
    POSTMORTEM Anticlimax: only thing that died was my VPN (openvpn) link to the cluster, so there was an exciting few seconds while it re-established. Everything else was fine. Starting back ntp everywhere. If you look at Marco's blog at http://my.opera.com/marcomarongiu/blog/2012/06/01/an-humble-attempt-to-work-around-the-leap-second - he has a solution for phasing the time change over 24 hours using ntpd -x to avoid the 1 second skip. Give that a go if it matters to you. For the systems I run, the jump isn't a problem. Just today, Sat June 30th - starting soon after the start of the day GMT. We've had a handful of blades in different datacentres as managed by different teams all go dark - not responding to pings, screen blank. They're all running Debian Squeeze - with everything from stock kernel to custom 3.2.21 builds. Most are Dell M610 blades, but I've also just lost a Dell R510 and other departments have lost machines from other vendors too. There was also an older IBM x3550 which crashed and which I thought might be unrelated, but now I'm wondering. The one crash which I did get a screen dump from said: [3161000.864001] BUG: spinlock lockup on CPU#1, ntpd/3358 [3161000.864001] lock: ffff88083fc0d740, .magic: dead4ead, .owner: imapd/24737, .owner_cpu: 0 Unfortunately the blades all supposedly had kdump configured, but they died so hard that kdump didn't trigger - and they had console blanking turned on. I've disabled console blanking now, so fingers crossed I'll have more information after the next crash. Just want to know if it's a common thread or "just us". It's really odd that they're different units in different datacentres bought at different times and run by different admins (I run the FastMail.FM ones)... and now even different vendor hardware. Most of the machines which crashed had been up for weeks/months and were running 3.1 or 3.2 series kernels. The most recent crash was a machine which had only been up about 6 hours running 3.2.21. THE WORKAROUND Ok people, here's how I worked around it. disabled ntp: /etc/init.d/ntp stop created http://linux.brong.fastmail.fm/2012-06-30/fixtime.pl (code stolen from Marco, see blog posts in comments) ran fixtime.pl without an argument to see that there was a leap second set ran fixtime.pl with an argument to remove the leap second NOTE: depends on adjtimex. I've put a copy of the squeeze adjtimex binary at http://linux.brong.fastmail.fm/2012-06-30/adjtimex - it will run without dependencies on a squeeze 64 bit system. If you put it in the same directory as fixtime.pl, it will be used if the system one isn't present. Obviously if you don't have squeeze 64 bit... find your own. I'm going to start ntp again tomorrow. As an anonymous user suggested - an alternative to running adjtimex is to just set the time yourself, which will presumably also clear the leapsecond counter.

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  • Radeon HD4850 serious issues when using DirectX 10

    - by ricsmania
    Hello, I have a problem with my video card. Whenever I run a DirectX 10 game, it works for a few seconds (10 or so) and then starts displaying nothing but big polygons. I have tested this with Crysis and Resident Evil 5, both have the same problems. The same games running under DirectX 9 work fine, except for some small black squares once in a while. I have the following specs: Asus P7P55D LE Intel Core i5 750 Sapphire Radeon HD4850 1GB 2x2GB Patriot Viper II Sector 5, DDR3 1600 MHz OCZ Stealth X Stream 500SXS 500W At first I thought it could be the video card overheating (it has stock cooling), but the game crashes even when it's running at 50 degrees C, and it's never been higher than 70. I also thought it could be the PSU, but as far as I know 500W is enough for this computer, especially because I haven't overclocked anything. My OS is Windows 7 X64 and I am using Catalyst 10.10, but I have also tried many older versions with no success. I don't think there is a problem with the card itself, or else it wouldn't run DirectX 9 games I believe. I have spent many hours searching for a solution but I couldn't, so any help is appreciated. Thank you. EDIT: I did some further investigation about the problem, and it seems taspeotis was right, it might be related to memory. I slightly underclocked the memory from 993 to 965 MHz and the problem went away completely. Both the black squares using DirectX 9 and the weird polygons using DirectX 10. I was using RE DirectX 10 Benchmark, as it consistently crashed around the same point, and now I can play the full benchmark with no artifacts at all. Unfortunately, the underclock has an obvious hit in performance. Although it's not critical, it's definitely noticeable. So, if the video memory test software showed no erros, but the card needs an underclock to work, what might be the problem? Temperature? Voltage? By the way, I couldn't find what the default voltage for this card is. And what is a good software to try and increase it? I tried Ati Tray Tools but it has a bug that increases the clock speed dramatically whenever I change something in the Overclock tab, so I'm afraid it might fry my card. Worst case scenario, if I don't find I solution I will try to slightly increase the GPU clock to compensate for the memory clock. Thank you again.

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  • I have been told to accept one error with Memtest86+

    - by DustByte
    Bought a new computer back in August with 4x4 GB RAM. Had problems with the RAM. They sent me four new sticks, which also generated errors. Singled out four sticks (from the eight I now had) that didn't generate any errors. Discovered by coincident a new RAM error last week (this time no BSOD). Contacted the company. According to them there have been issues with a bad stock from last summer so I got two tested 8 GB sticks sent to me. Been running Memtest86+ over the weekend. After 20 hours I got an error (see attached photo). The test has now been running for 37 hours but so far only this one error. I contacted the company where I bought the computer. They wrote back: I wouldn't worry about hat one fail. We have had similar situations here whereby it passes numerous times but then fails once. We think it's an issue with memtest, after all memory is faulty or it isn't so you can't really have it pass a few times, fail the next time around and then pass again! Please trust me on this and continue with the memory we sent you and if your problems continue we'll look at getting it replaced again. I gather from other forum posts that many people do not accept a single error. What could this single error signify, faulty RAM or a glitch in the MEMTEST program (or other)? Update: From the helpful comments below I conclude that an occasional (and rare) "random" error could occur and be acceptable, but repeated errors at the same address would indicate malfunction. Memtest has now run for 45 hours and I still have only one error. For everyone's information, I will keep running the test. In less than two days I am going away for a month. I will most likely leave Memtest running. As I do not have a UPS there is a risk that a power outage will ruin the experiment. The computer is a desktop so I cannot bring it with me (which would curiously have exposed it to more cosmic rays as I will be flying ;)).

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  • What else can I do to secure my Linux server?

    - by eric01
    I want to put a web application on my Linux server: I will first explain to you what the web app will do and then I will tell you what I did so far to secure my brand new Linux system. The app will be a classified ads website (like gumtree.co.uk) where users can sell their items, upload images, send to and receive emails from the admin. It will use SSL for some pages. I will need SSH. So far, what I did to secure my stock Ubuntu (latest version) is the following: NOTE: I probably did some things that will prevent the application from doing all its tasks, so please let me know of that. My machine's sole purpose will be hosting the website. (I put numbers as bullet points so you can refer to them more easily) 1) Firewall I installed Uncomplicated Firewall. Deny IN & OUT by default Rules: Allow IN & OUT: HTTP, IMAP, POP3, SMTP, SSH, UDP port 53 (DNS), UDP port 123 (SNTP), SSL, port 443 (the ones I didn't allow were FTP, NFS, Samba, VNC, CUPS) When I install MySQL & Apache, I will open up Port 3306 IN & OUT. 2) Secure the partition in /etc/fstab, I added the following line at the end: tmpfs /dev/shm tmpfs defaults,rw 0 0 Then in console: mount -o remount /dev/shm 3) Secure the kernel In the file /etc/sysctl.conf, there are a few different filters to uncomment. I didn't know which one was relevant to web app hosting. Which one should I activate? They are the following: A) Turn on Source Address Verification in all interfaces to prevent spoofing attacks B) Uncomment the next line to enable packet forwarding for IPv4 C) Uncomment the next line to enable packet forwarding for IPv6 D) Do no accept ICMP redirects (we are not a router) E) Accept ICMP redirects only for gateways listed in our default gateway list F) Do not send ICMP redirects G) Do not accept IP source route packets (we are not a router) H) Log Martian Packets 4) Configure the passwd file Replace "sh" by "false" for all accounts except user account and root. I also did it for the account called sshd. I am not sure whether it will prevent SSH connection (which I want to use) or if it's something else. 5) Configure the shadow file In the console: passwd -l to lock all accounts except user account. 6) Install rkhunter and chkrootkit 7) Install Bum Disabled those services: "High performance mail server", "unreadable (kerneloops)","unreadable (speech-dispatcher)","Restores DNS" (should this one stay on?) 8) Install Apparmor_profiles 9) Install clamav & freshclam (antivirus and update) What did I do wrong and what should I do more to secure this Linux machine? Thanks a lot in advance

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  • Controller Action Methods with different signatures

    - by Narsil
    I am trying to get my URLs in files/id format. I am guessing I should have two Index methods in my controller, one with a parameter and one with not. But I get this error message in browser below. Anyway here is my controller methods: public ActionResult Index() { return Content("Index "); } // // GET: /Files/5 public ActionResult Index(int id) { File file = fileRepository.GetFile(id); if (file == null) return Content("Not Found"); else return Content(file.FileID.ToString()); } Error: Server Error in '/' Application. The current request for action 'Index' on controller type 'FilesController' is ambiguous between the following action methods: System.Web.Mvc.ActionResult Index() on type FileHosting.Controllers.FilesController System.Web.Mvc.ActionResult Index(Int32) on type FileHosting.Controllers.FilesController Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Reflection.AmbiguousMatchException: The current request for action 'Index' on controller type 'FilesController' is ambiguous between the following action methods: System.Web.Mvc.ActionResult Index() on type FileHosting.Controllers.FilesController System.Web.Mvc.ActionResult Index(Int32) on type FileHosting.Controllers.FilesController Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [AmbiguousMatchException: The current request for action 'Index' on controller type 'FilesController' is ambiguous between the following action methods: System.Web.Mvc.ActionResult Index() on type FileHosting.Controllers.FilesController System.Web.Mvc.ActionResult Index(Int32) on type FileHosting.Controllers.FilesController] System.Web.Mvc.ActionMethodSelector.FindActionMethod(ControllerContext controllerContext, String actionName) +396292 System.Web.Mvc.ReflectedControllerDescriptor.FindAction(ControllerContext controllerContext, String actionName) +62 System.Web.Mvc.ControllerActionInvoker.FindAction(ControllerContext controllerContext, ControllerDescriptor controllerDescriptor, String actionName) +13 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +99 System.Web.Mvc.Controller.ExecuteCore() +105 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +39 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7 System.Web.Mvc.<c_DisplayClass8.b_4() +34 System.Web.Mvc.Async.<c_DisplayClass1.b_0() +21 System.Web.Mvc.Async.<c__DisplayClass81.<BeginSynchronous>b__7(IAsyncResult _) +12 System.Web.Mvc.Async.WrappedAsyncResult1.End() +59 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +44 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +7 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677678 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Updated Code: public ActionResult Index(int? id) { if (id.HasValue) { File file = fileRepository.GetFile(id.Value); if (file == null) return Content("Not Found"); else return Content(file.FileID.ToString()); } else return Content("Index"); } It's still not the thing I want. URLs have to be in files?id=3 format. I want files/3 routes from global.asax routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); //files/3 //it's the one I wrote routes.MapRoute("Files", "{controller}/{id}", new { controller = "Files", action = "Index", id = UrlParameter.Optional} ); I tried adding a new route after reading Jeff's post but I can't get it working. It still works with files?id=2 though.

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  • Doing TDD Silverlight 4 RC using Visual Studio 2010 RC

    - by user133992
    First I am glad to see better TDD support in VS2010. Support for generating code stubs from my tests is ok - not as good as more mature TDD plug-ins but a good start. I am looking for some best Silverlight 4.0 TDD practices. First Question: Anyone have links, recommendations? I know the new Silverlight Unit Test capabilities are much better (Jeff Wilcox's Mix Presentation). What I am focusing on right now is using TDD to develop pure Silverlight 4.0 Class Library projects - projects without a Silverlight UI project. I've been able to get it to work but not as cleanly as it should be. I can create an Empty VS project. Add A Silverlight 4 Class Library Project. Add a TestProject (not a silverlight Unit Test Project but a plain Test Project). Add a simple test in the Test Project such as: namespace Calculator.Test { [TestClass] public class CalculatorTests { [TestMethod] public void CalulatorAddTest() { Calc c = new Calc(); int expected = 10; int actual = c.Add(6, 4); Assert.AreEqual<int>(expected, actual); } } } Using the new Generate Type and Method from Test feature it will generate the following code in the Silverlight Project: namespace Calculator { public class Calc { public int Add(int p, int p_2) { throw new NotImplementedException(); } } } When I run the tests the first time it says the target assembly is Silverlight and not able to run test - Not exact text but the same general idea. When I change the implementation to: namespace Calculator { public class Calc { public int Add(int p, int p_2) { return p + p_2; } } } and re-run the test, it works fine and the test goes green. It also works for all other TDD code I generate after. I also get a warning Mark in the Test Project's reference to the Calculator Silverlight Class Library Assembly. Second Question: Any comments ideas if this just a bug in VS2010 RC or is Silverlight Class Library TDD not really supported. I have not created a Silverlight UI project or changed and build or debug settings so I have no idea what is hosting the silverlight DLL. Finally, some of the Silverlight Class Libraries I need to write will provide functionality that requires elevated Out-Of-Browser rights. Based on the above, it looks like I can use TDD Test Projects against regular Silverlight 4.0 Class Libraries, but I have no idea how I can TDD the elevated OOB functionality without also creating the UI component that gets installed. The UI piece is not really needed for the Library development and gets in the way of what I actually want to TDD. I know I can (and will) mock some of that functionality but at some point I will also need the real thing in my tests. Third Question: Any ideas how to TDD Silverlight 4.0 Class Library project that requires OOB elevated rights? Thanks!

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  • Haskell: Left-biased/short-circuiting function

    - by user2967411
    Two classes ago, our professor presented to us a Parser module. Here is the code: module Parser (Parser,parser,runParser,satisfy,char,string,many,many1,(+++)) where import Data.Char import Control.Monad import Control.Monad.State type Parser = StateT String [] runParser :: Parser a -> String -> [(a,String)] runParser = runStateT parser :: (String -> [(a,String)]) -> Parser a parser = StateT satisfy :: (Char -> Bool) -> Parser Char satisfy f = parser $ \s -> case s of [] -> [] a:as -> [(a,as) | f a] char :: Char -> Parser Char char = satisfy . (==) alpha,digit :: Parser Char alpha = satisfy isAlpha digit = satisfy isDigit string :: String -> Parser String string = mapM char infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a (+++) = mplus many, many1 :: Parser a -> Parser [a] many p = return [] +++ many1 p many1 p = liftM2 (:) p (many p) Today he gave us an assignment to introduce "a left-biased, or short-circuiting version of (+++)", called (<++). His hint was for us to consider the original implementation of (+++). When he first introduced +++ to us, this was the code he wrote, which I am going to call the original implementation: infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a p +++ q = Parser $ \s -> runParser p s ++ runParser q s I have been having tons of trouble since we were introduced to parsing and so it continues. I have tried/am considering two approaches. 1) Use the "original" implementation, as in p +++ q = Parser $ \s - runParser p s ++ runParser q s 2) Use the final implementation, as in (+++) = mplus Here are my questions: 1) The module will not compile if I use the original implementation. The error: Not in scope: data constructor 'Parser'. It compiles fine using (+++) = mplus. What is wrong with using the original implementation that is avoided by using the final implementation? 2) How do I check if the first Parser returns anything? Is something like (not (isNothing (Parser $ \s - runParser p s) on the right track? It seems like it should be easy but I have no idea. 3) Once I figure out how to check if the first Parser returns anything, if I am to base my code on the final implementation, would it be as easy as this?: -- if p returns something then p <++ q = mplus (Parser $ \s -> runParser p s) mzero -- else (<++) = mplus Best, Jeff

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  • Why is two-way binding in silverlight not working?

    - by Edward Tanguay
    According to how Silverlight TwoWay binding works, when I change the data in the FirstName field, it should change the value in CheckFirstName field. Why is this not the case? ANSWER: Thank you Jeff, that was it, for others: here is the full solution with downloadable code. XAML: <StackPanel> <Grid x:Name="GridCustomerDetails"> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto"/> <ColumnDefinition Width="300"/> </Grid.ColumnDefinitions> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="0" Grid.Column="0">First Name:</TextBlock> <TextBox Margin="10" Grid.Row="0" Grid.Column="1" Text="{Binding FirstName, Mode=TwoWay}"/> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="1" Grid.Column="0">Last Name:</TextBlock> <TextBox Margin="10" Grid.Row="1" Grid.Column="1" Text="{Binding LastName}"/> <TextBlock VerticalAlignment="Center" Margin="10" Grid.Row="2" Grid.Column="0">Address:</TextBlock> <TextBox Margin="10" Grid.Row="2" Grid.Column="1" Text="{Binding Address}"/> </Grid> <Border Background="Tan" Margin="10"> <TextBlock x:Name="CheckFirstName"/> </Border> </StackPanel> Code behind: public Page() { InitializeComponent(); Customer customer = new Customer(); customer.FirstName = "Jim"; customer.LastName = "Taylor"; customer.Address = "72384 South Northern Blvd."; GridCustomerDetails.DataContext = customer; Customer customerOutput = (Customer)GridCustomerDetails.DataContext; CheckFirstName.Text = customer.FirstName; }

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  • Is READ UNCOMMITTED / NOLOCK safe in this situation?

    - by Ben Challenor
    I know that snapshot isolation would fix this problem, but I'm wondering if NOLOCK is safe in this specific case so that I can avoid the overhead. I have a table that looks something like this: drop table Data create table Data ( Id BIGINT NOT NULL, Date BIGINT NOT NULL, Value BIGINT, constraint Cx primary key (Date, Id) ) create nonclustered index Ix on Data (Id, Date) There are no updates to the table, ever. Deletes can occur but they should never contend with the SELECT because they affect the other, older end of the table. Inserts are regular and page splits to the (Id, Date) index are extremely common. I have a deadlock situation between a standard INSERT and a SELECT that looks like this: select top 1 Date, Value from Data where Id = @p0 order by Date desc because the INSERT acquires a lock on Cx (Date, Id; Value) and then Ix (Id, Date), but the SELECT acquires a lock on Ix (Id, Date) and then Cx (Date, Id; Value). This is because the SELECT first seeks on Ix and then joins to a seek on Cx. Swapping the clustered and non-clustered index would break this cycle, but it is not an acceptable solution because it would introduce cycles with other (more complex) SELECTs. If I add NOLOCK to the SELECT, can it go wrong in this case? Can it return: More than one row, even though I asked for TOP 1? No rows, even though one exists and has been committed? Worst of all, a row that doesn't satisfy the WHERE clause? I've done a lot of reading about this online, but the only reproductions of over- or under-count anomalies I've seen (one, two) involve a scan. This involves only seeks. Jeff Atwood has a post about using NOLOCK that generated a good discussion. I was particularly interested in a comment by Rick Townsend: Secondly, if you read dirty data, the risk you run is of reading the entirely wrong row. For example, if your select reads an index to find your row, then the update changes the location of the rows (e.g.: due to a page split or an update to the clustered index), when your select goes to read the actual data row, it's either no longer there, or a different row altogether! Is this possible with inserts only, and no updates? If so, then I guess even my seeks on an insert-only table could be dangerous. Update: I'm trying to figure out how snapshot isolation works. It seems to be row-based, where transactions read the table (with no shared lock!), find the row they are interested in, and then see if they need to get an old version of the row from the version store in tempdb. But in my case, no row will have more than one version, so the version store seems rather pointless. And if the row was found with no shared lock, how is it different to just using NOLOCK?

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  • Autocomplete server-side implementation

    - by toluju
    What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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  • Why does the following Java Script fail to load XML?

    - by Pavitar
    I have taken an example taught to us in class,wherein a javascript is used to retrieve data from the XML,but it doesn't work.Please help I have also added the XML file below. <html> <head> <title>Customer Info</title> <script language="javascript"> var xmlDoc = 0; var xmlObj = 0; function loadCustomers(){ xmlDoc = new ActiveXObject("Microsoft.XMLDOM"); xmlDoc.async = "false"; xmlDoc.onreadystatechange = displayCustomers; xmlDoc.load("customers.xml"); } function displayCustomers(){ if(xmlDoc.readyState == 4){ xmlObj = xmlDoc.documentElement; var len = xmlObj.childNodes.length; for(i = 0; i < len; i++){ var nodeElement = xmlObj.childNodes[i]; document.write(nodeElement.attributes[0].value); for(j = 0; j < nodeElement.childNodes.length; j++){ document.write(" " + nodeElement.childNodes[j].firstChild.nodeValue); } document.write("<br/>"); } } } </script> </head> <body> <form> <input type="button" value="Load XML" onClick="loadCustomers()"> </form> </body> </html> XML(customers.xml) <?xml version="1.0" encoding="UTF-8"?> <customers> <customer custid="CU101"> <pwd>PW101</pwd> <email>[email protected]</email> </customer> <customer custid="CU102"> <pwd>PW102</pwd> <email>[email protected]</email> </customer> <customer custid="CU103"> <pwd>PW103</pwd> <email>[email protected]</email> </customer> <customer custid="CU104"> <pwd>PW104</pwd> <email>[email protected]</email> </customer> </customers>

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  • Multiple column subselect in mysql 5 (5.1.42)

    - by rubber boots
    This one seems to be a simple problem, but I can't make it work in a single select or nested select. Retrieve the authors and (if any) advisers of a paper (article) into one row. I order to explain the problem, here are the two data tables (pseudo) papers (id, title, c_year) persons (id, firstname, lastname) plus a link table w/one extra attribute (pseudo): paper_person_roles( paper_id person_id act_role ENUM ('AUTHOR', 'ADVISER') ) This is basically a list of written papers (table: papers) and a list of staff and/or students (table: persons) An article my have (1,N) authors. An article may have (0,N) advisers. A person can be in 'AUTHOR' or 'ADVISER' role (but not at the same time). The application eventually puts out table rows containing the following entries: TH: || Paper_ID | Author(s) | Title | Adviser(s) | TD: || 21334 |John Doe, Jeff Tucker|Why the moon looks yellow|Brown, Rayleigh| ... My first approach was like: select/extract a full list of articles into the application, eg.SELECT q.id, q.title FROM papers AS q ORDER BY q.c_year and save the results of the query into an array (in the application). After this step, loop over the array of the returned information and retrieve authors and advisers (if any), via prepared statement (? is the paper's id) from the link table like:APPLICATION_LOOP(paper_ids in array) SELECT p.lastname, p.firstname, r.act_role FROM persons AS p, paper_person_roles AS r WHERE p.id=r.person_id AND r.paper_id = ? # The application does further processing from here (pseudo): foreach record from resulting records if record.act_role eq 'AUTHOR' then join to author_column if record.act_role eq 'ADVISER' then join to avdiser_column end print id, author_column, title, adviser_column APPLICATION_LOOP This works so far and gives the desired output. Would it make sense to put the computation back into the DB? I'm not very proficient in nontrivial SQL and can't find a solution with a single (combined or nested) select call. I tried sth. like SELECT q.title (CONCAT_WS(' ', (SELECT p.firstname, p.lastname AS aunames FROM persons AS p, paper_person_roles AS r WHERE q.id=r.paper_id AND r.act_role='AUTHOR') ) ) AS aulist FROM papers AS q, persons AS p, paper_person_roles AS r in several variations, but no luck ... Maybe there is some chance? Thanks in advance r.b.

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  • Top 20 Daily Deal Sites In India

    - by Damodhar
    If you have never heard of Groupon recently, you probably are not working in the tech industry because it is all over the blogosphere. After all, growing from zero to US$1.35 billion valuation in 18 months is pretty AMAZING. Inspired by this, the following bunch of Groupon clone’s are already rising in India. Definitely this business model is emerging and changes the way online shopping happens in India. SnapDeal SnapDeal features a Best deals Coupons at an unbeatable price on the best stuff to do, see, eat, and buy in our city. It provides vouchers and discounts in all the major cities like Delhi, Mumbai, Chennai and Bangalore. KhojGuru Exclusive Discount coupons from hundreds of brands and retailers. These discounts can be easily downloaded as an SMS on to the mobile phone or their print out can be taken. MyDala A platform which gets us great deals in our city.Leveraging the “power of group buying”. Group buying happens when like minded people come together to get deals that we can never get on our own as individuals. SoSasta Great place which would not only tell us about the hidden treasures of our city — but also made them affordable to us at the end of the month. DealsAndYou Deals and You is a group buying portal that features a daily deal on the best stuff in some of India’s leading cities. AajKaCatch Its concept is to provide you the most unique, useful and qualitative product at a very low price. So you can now shop without the hassles of clustered products. BindassBargain Bindaas Bargain offers a new deal every day! Great stuff ranging from cool gadgets, home theatres, luxury watches, smash games. MasthiDeals It get you a great deal on a great stuff to do, eat, buy or see in your city. They have a team of about 25 wonderful people working in Chennai office working side by side with folks in MasthiDeal’s other cities. Koovs Founded by a team of IIT alumni who have brought in their expertise from the internet industry. Koovs is a Bangalore based start up and one point solution for all your desires. Taggle It brings you a variety of offers from some of the most respected brands in the country.This website uses collective buying to create a win-win for local businesses and their customers. BuzzInTown Buzzintown.com is a portal owned by Wortal Inc. There are a US headquartered company, with a presence pan-India through their India subsidiary, managed by a vastly experienced set of global leaders from the media, entertainment and technology industries. BuyThePrice It lines up the best win – win deals for both consumers and vendors and also ensures that each of the orders are dispatched in the shortest time possible. 24HoursLoot 24hoursLoot is an online store for selling a new t-shirt (sometime other products) everyday at deep discounted price in limited quantity/stock. DealMagic Customers get exposure to the best their city has to offer, at unbeatable prices (50-90% off).  We never feature more than one business on our website on any given day, so we have to be very very selective on who gets featured. Dealivore ICUMI Technologies Pvt Ltd is the company operating the Dealivore service. Founded in December 2009, ICUMI is privately owned and funded. LootMore An online store that exclusively focuses on selling cool quality stuff at cheap prices. Here you’ll always find the latest and greatest brands at prices you can afford. Foodome The deals features the best coupons at an unbeatable price on restaurants, fine dining on where to spend your birthday party.They provide coupon only in Chennai as of now. Top Online Shopping Sites- Nation Wide ebay.in eBay is The World’s Online Marketplace, enabling trade on a local, national and international basis. With a diverse and passionate community of individuals and small businesses, eBay offers an online platform where millions of items are traded each day. FutureBazzar Future Group, led by its founder and Group CEO, Mr. Kishore Biyani, is one of India’s leading business houses with multiple businesses spanning across the consumption space. TradeUs Launched in July 2009 and in a short span of time it has turned into one of India’s foremost shopping portals setting the Indian e-commerce abode aflame. BigShoeBazzar (BSB) is the largest online authorized shoe store in South Asia. Croma Promoted by Infiniti Retail Ltd, a 100% subsidiary of Tata Sons.One of the world’s leading retailers, ensuring that you buy nothing but the best. This article titled,Top 20 Daily Deal Sites In India, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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