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• Strange Recurrent Excessive I/O Wait

  - by Chris

  I know quite well that I/O wait has been discussed multiple times on this site, but all the other topics seem to cover constant I/O latency, while the I/O problem we need to solve on our server occurs at irregular (short) intervals, but is ever-present with massive spikes of up to 20k ms a-wait and service times of 2 seconds. The disk affected is /dev/sdb (Seagate Barracuda, for details see below). A typical iostat -x output would at times look like this, which is an extreme sample but by no means rare: iostat (Oct 6, 2013) tps rd_sec/s wr_sec/s avgrq-sz avgqu-sz await svctm %util 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 16.00 0.00 156.00 9.75 21.89 288.12 36.00 57.60 5.50 0.00 44.00 8.00 48.79 2194.18 181.82 100.00 2.00 0.00 16.00 8.00 46.49 3397.00 500.00 100.00 4.50 0.00 40.00 8.89 43.73 5581.78 222.22 100.00 14.50 0.00 148.00 10.21 13.76 5909.24 68.97 100.00 1.50 0.00 12.00 8.00 8.57 7150.67 666.67 100.00 0.50 0.00 4.00 8.00 6.31 10168.00 2000.00 100.00 2.00 0.00 16.00 8.00 5.27 11001.00 500.00 100.00 0.50 0.00 4.00 8.00 2.96 17080.00 2000.00 100.00 34.00 0.00 1324.00 9.88 1.32 137.84 4.45 59.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 22.00 44.00 204.00 11.27 0.01 0.27 0.27 0.60 Let me provide you with some more information regarding the hardware. It's a Dell 1950 III box with Debian as OS where uname -a reports the following: Linux xx 2.6.32-5-amd64 #1 SMP Fri Feb 15 15:39:52 UTC 2013 x86_64 GNU/Linux The machine is a dedicated server that hosts an online game without any databases or I/O heavy applications running. The core application consumes about 0.8 of the 8 GBytes RAM, and the average CPU load is relatively low. The game itself, however, reacts rather sensitive towards I/O latency and thus our players experience massive ingame lag, which we would like to address as soon as possible. iostat: avg-cpu: %user %nice %system %iowait %steal %idle 1.77 0.01 1.05 1.59 0.00 95.58 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn sdb 13.16 25.42 135.12 504701011 2682640656 sda 1.52 0.74 20.63 14644533 409684488 Uptime is: 19:26:26 up 229 days, 17:26, 4 users, load average: 0.36, 0.37, 0.32 Harddisk controller: 01:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 1078 (rev 04) Harddisks: Array 1, RAID-1, 2x Seagate Cheetah 15K.5 73 GB SAS Array 2, RAID-1, 2x Seagate ST3500620SS Barracuda ES.2 500GB 16MB 7200RPM SAS Partition information from df: Filesystem 1K-blocks Used Available Use% Mounted on /dev/sdb1 480191156 30715200 425083668 7% /home /dev/sda2 7692908 437436 6864692 6% / /dev/sda5 15377820 1398916 13197748 10% /usr /dev/sda6 39159724 19158340 18012140 52% /var Some more data samples generated with iostat -dx sdb 1 (Oct 11, 2013) Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sdb 0.00 15.00 0.00 70.00 0.00 656.00 9.37 4.50 1.83 4.80 33.60 sdb 0.00 0.00 0.00 2.00 0.00 16.00 8.00 12.00 836.00 500.00 100.00 sdb 0.00 0.00 0.00 3.00 0.00 32.00 10.67 9.96 1990.67 333.33 100.00 sdb 0.00 0.00 0.00 4.00 0.00 40.00 10.00 6.96 3075.00 250.00 100.00 sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.00 0.00 0.00 100.00 sdb 0.00 0.00 0.00 2.00 0.00 16.00 8.00 2.62 4648.00 500.00 100.00 sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 100.00 sdb 0.00 0.00 0.00 1.00 0.00 16.00 16.00 1.69 7024.00 1000.00 100.00 sdb 0.00 74.00 0.00 124.00 0.00 1584.00 12.77 1.09 67.94 6.94 86.00 Characteristic charts generated with rrdtool can be found here: iostat plot 1, 24 min interval: http://imageshack.us/photo/my-images/600/yqm3.png/ iostat plot 2, 120 min interval: http://imageshack.us/photo/my-images/407/griw.png/ As we have a rather large cache of 5.5 GBytes, we thought it might be a good idea to test if the I/O wait spikes would perhaps be caused by cache miss events. Therefore, we did a sync and then this to flush the cache and buffers: echo 3 > /proc/sys/vm/drop_caches and directly afterwards the I/O wait and service times virtually went through the roof, and everything on the machine felt like slow motion. During the next few hours the latency recovered and everything was as before - small to medium lags in short, unpredictable intervals. Now my question is: does anybody have any idea what might cause this annoying behaviour? Is it the first indication of the disk array or the raid controller dying, or something that can be easily mended by rebooting? (At the moment we're very reluctant to do this, however, because we're afraid that the disks might not come back up again.) Any help is greatly appreciated. Thanks in advance, Chris. Edited to add: we do see one or two processes go to 'D' state in top, one of which seems to be kjournald rather frequently. If I'm not mistaken, however, this does not indicate the processes causing the latency, but rather those affected by it - correct me if I'm wrong. Does the information about uninterruptibly sleeping processes help us in any way to address the problem? @Andy Shinn requested smartctl data, here it is: smartctl -a -d megaraid,2 /dev/sdb yields: smartctl 5.40 2010-07-12 r3124 [x86_64-unknown-linux-gnu] (local build) Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net Device: SEAGATE ST3500620SS Version: MS05 Serial number: Device type: disk Transport protocol: SAS Local Time is: Mon Oct 14 20:37:13 2013 CEST Device supports SMART and is Enabled Temperature Warning Disabled or Not Supported SMART Health Status: OK Current Drive Temperature: 20 C Drive Trip Temperature: 68 C Elements in grown defect list: 0 Vendor (Seagate) cache information Blocks sent to initiator = 1236631092 Blocks received from initiator = 1097862364 Blocks read from cache and sent to initiator = 1383620256 Number of read and write commands whose size <= segment size = 531295338 Number of read and write commands whose size > segment size = 51986460 Vendor (Seagate/Hitachi) factory information number of hours powered up = 36556.93 number of minutes until next internal SMART test = 32 Error counter log: Errors Corrected by Total Correction Gigabytes Total ECC rereads/ errors algorithm processed uncorrected fast | delayed rewrites corrected invocations [10^9 bytes] errors read: 509271032 47 0 509271079 509271079 20981.423 0 write: 0 0 0 0 0 5022.039 0 verify: 1870931090 196 0 1870931286 1870931286 100558.708 0 Non-medium error count: 0 SMART Self-test log Num Test Status segment LifeTime LBA_first_err [SK ASC ASQ] Description number (hours) # 1 Background short Completed 16 36538 - [- - -] # 2 Background short Completed 16 36514 - [- - -] # 3 Background short Completed 16 36490 - [- - -] # 4 Background short Completed 16 36466 - [- - -] # 5 Background short Completed 16 36442 - [- - -] # 6 Background long Completed 16 36420 - [- - -] # 7 Background short Completed 16 36394 - [- - -] # 8 Background short Completed 16 36370 - [- - -] # 9 Background long Completed 16 36364 - [- - -] #10 Background short Completed 16 36361 - [- - -] #11 Background long Completed 16 2 - [- - -] #12 Background short Completed 16 0 - [- - -] Long (extended) Self Test duration: 6798 seconds [113.3 minutes] smartctl -a -d megaraid,3 /dev/sdb yields: smartctl 5.40 2010-07-12 r3124 [x86_64-unknown-linux-gnu] (local build) Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net Device: SEAGATE ST3500620SS Version: MS05 Serial number: Device type: disk Transport protocol: SAS Local Time is: Mon Oct 14 20:37:26 2013 CEST Device supports SMART and is Enabled Temperature Warning Disabled or Not Supported SMART Health Status: OK Current Drive Temperature: 19 C Drive Trip Temperature: 68 C Elements in grown defect list: 0 Vendor (Seagate) cache information Blocks sent to initiator = 288745640 Blocks received from initiator = 1097848399 Blocks read from cache and sent to initiator = 1304149705 Number of read and write commands whose size <= segment size = 527414694 Number of read and write commands whose size > segment size = 51986460 Vendor (Seagate/Hitachi) factory information number of hours powered up = 36596.83 number of minutes until next internal SMART test = 28 Error counter log: Errors Corrected by Total Correction Gigabytes Total ECC rereads/ errors algorithm processed uncorrected fast | delayed rewrites corrected invocations [10^9 bytes] errors read: 610862490 44 0 610862534 610862534 20470.133 0 write: 0 0 0 0 0 5022.480 0 verify: 2861227413 203 0 2861227616 2861227616 100872.443 0 Non-medium error count: 1 SMART Self-test log Num Test Status segment LifeTime LBA_first_err [SK ASC ASQ] Description number (hours) # 1 Background short Completed 16 36580 - [- - -] # 2 Background short Completed 16 36556 - [- - -] # 3 Background short Completed 16 36532 - [- - -] # 4 Background short Completed 16 36508 - [- - -] # 5 Background short Completed 16 36484 - [- - -] # 6 Background long Completed 16 36462 - [- - -] # 7 Background short Completed 16 36436 - [- - -] # 8 Background short Completed 16 36412 - [- - -] # 9 Background long Completed 16 36404 - [- - -] #10 Background short Completed 16 36401 - [- - -] #11 Background long Completed 16 2 - [- - -] #12 Background short Completed 16 0 - [- - -] Long (extended) Self Test duration: 6798 seconds [113.3 minutes]

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• Java: matching two different type of array

  - by sling

  Hi, I am doing a password login that requires me to match two array: User and Pass. If user key in "mark" and "pass", it should show successfully. However I have trouble with the String[] input = pass.getPassword(); and the matching of the two arrays. String[] User = {"mark", "susan", "bobo"}; String[] Pass = {"pass", "word", "password"}; String[] input = pass.getPassword(); if(Pass.length == input.length && user.getText().equals(User)) { lblstat.setForeground(Color.GREEN); lblstat.setText("Successful"); } else { lblstat.setForeground(Color.RED); lblstat.setText("Failed"); }

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• fancybox auto load

  - by dolomite

  <script type="text/javascript"> $(document).ready(function() { $("a[rel=example_group]").fancybox({ 'transitionIn' : 'none', 'transitionOut' : 'none', 'titlePosition' : 'over', 'titleFormat' : function(title, currentArray, currentIndex, currentOpts) { return '<span id="fancybox-title-over">Image ' + (currentIndex + 1) + ' / ' + currentArray.length + (title.length ? ' &nbsp; ' + title : '') + '</span>'; } }); $("#lightbox_trigger").fancybox({ 'titlePosition' : 'inside', 'transitionIn' : 'none', 'transitionOut' : 'none' }); }); jQuery(document).ready(function() { $("#lightbox_trigger").trigger('click'); }); that works fine, the click event triggers the lightbox..but what if I remove the link with the id #lightbox_trigger? Basically what I want it the lightbox to load without the click event and link.. anyone?

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• Simple javascript string problem in ie6 and ie7

  - by Jeff Lamb

  I have a very simple function that takes a list of comma separated (x,y) points and imports them into a graph. I have FF, Chrome and IE8 installed. I use IETester to test for IE6 and IE7. // Import Data this.Import = function(data) { alert("Data in: "+data); var d; // Make sure the first and the last are start/ending parenthesis if ( (data[0] != '(') || (data[data.length-1] != ')') ) { alert("After if: "+data[0]+" "+data[data.length-1]); return false; } ... In Chrome, FF and IE8, I don't see the "After if:" alert. In IE6 and IE7, I see the following two alerts: Data in: (52,16),(100,90) After if: undefined undefined The "Data in" alert matches in all browsers. Any ideas?

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• global scope of variable

  - by shantanuo

  The following shell scrip will check the disk space and change the variable "diskfull" to 1 if the usage is more than 10% The last echo always shows 0 I tried the global diskfull=1 in the if clause but it did not work. How do I change the variable to 1 if the disk consumed is more than 10% #!/bin/sh diskfull=0 ALERT=10 df -HP | grep -vE '^Filesystem|tmpfs|cdrom' | awk '{ print $5 " " $1 }' | while read output; do #echo $output usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1 ) partition=$(echo $output | awk '{ print $2 }' ) if [ $usep -ge $ALERT ]; then diskfull=1 exit fi done echo $diskfull

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• memcpy segmentation fault on linux but not os x

  - by Andre

  I'm working on implementing a log based file system for a file as a class project. I have a good amount of it working on my 64 bit OS X laptop, but when I try to run the code on the CS department's 32 bit linux machines, I get a seg fault. The API we're given allows writing DISK_SECTOR_SIZE (512) bytes at a time. Our log record consists of the 512 bytes the user wants to write as well as some metadata (which sector he wants to write to, the type of operation, etc). All in all, the size of the "record" object is 528 bytes, which means each log record spans 2 sectors on the disk. The first record writes 0-512 on sector 0, and 0-15 on sector 1. The second record writes 16-512 on sector 1, and 0-31 on sector 2. The third record writes 32-512 on sector 2, and 0-47 on sector 3. ETC. So what I do is read the two sectors I'll be modifying into 2 freshly allocated buffers, copy starting at record into buf1+the calculated offset for 512-offset bytes. This works correctly on both machines. However, the second memcpy fails. Specifically, "record+DISK_SECTOR_SIZE-offset" in the below code segfaults, but only on the linux machine. Running some random tests, it gets more curious. The linux machine reports sizeof(Record) to be 528. Therefore, if I tried to memcpy from record+500 into buf for 1 byte, it shouldn't have a problem. In fact, the biggest offset I can get from record is 254. That is, memcpy(buf1, record+254, 1) works, but memcpy(buf1, record+255, 1) segfaults. Does anyone know what I'm missing? Record *record = malloc(sizeof(Record)); record->tid = tid; record->opType = OP_WRITE; record->opArg = sector; int i; for (i = 0; i < DISK_SECTOR_SIZE; i++) { record->data[i] = buf[i]; // *buf is passed into this function } char* buf1 = malloc(DISK_SECTOR_SIZE); char* buf2 = malloc(DISK_SECTOR_SIZE); d_read(ad->disk, ad->curLogSector, buf1); d_read(ad->disk, ad->curLogSector+1, buf2); memcpy(buf1+offset, record, DISK_SECTOR_SIZE-offset); memcpy(buf2, record+DISK_SECTOR_SIZE-offset, offset+sizeof(Record)-sizeof(record->data));

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• Matlab Image watermarking question , using both SVD and DWT

  - by Georgek

  Hello all . here is a code that i got over the net ,and it is supposed to embed a watermark of size(50*20) called _copyright.bmp in the Code below . the size of the cover object is (512*512), it is called _lena_std_bw.bmp.What we did here is we did DWT2 2 times for the image , when we reached our second dwt2 cA2 size is 128*128. You should notice that the blocksize and it equals 4, it is used to determine the max msg size based on cA2 according to the following code:max_message=RcA2*CcA2/(blocksize^2). in our current case max_message would equal 128*128/(4^2)=1024. i want to embed a bigger watermark in the 2nd dwt2 and lets say the size of that watermark is 400*10(i can change the dimension using MS PAINT), what i have to do is change the size of the blocksize to 2. so max_message=4096.Matlab gives me 3 errors and they are : ??? Error using == plus Matrix dimensions must agree. Error in == idwt2 at 93 x = upsconv2(a,{Lo_R,Lo_R},sx,dwtEXTM,shift)+ ... % Approximation. Error in == two_dwt_svd_low_low at 88 CAA1 = idwt2(cA22,cH2,cV2,cD2,'haar',[RcA1,CcA1]); The origional Code is (the origional code where blocksize =4): %This algorithm makes DWT for the whole image and after that make DWT for %cH1 and make SVD for cH2 and embed the watermark in every level after SVD %(1) -------------- Embed Watermark ------------------------------------ %Add the watermar W to original image I and give the watermarked image in J %-------------------------------------------------------------------------- % set the gain factor for embeding and threshold for evaluation clc; clear all; close all; % save start time start_time=cputime; % set the value of threshold and alpha thresh=.5; alpha =0.01; % read in the cover object file_name='_lena_std_bw.bmp'; cover_object=double(imread(file_name)); % determine size of watermarked image Mc=size(cover_object,1); %Height Nc=size(cover_object,2); %Width % read in the message image and reshape it into a vector file_name='_copyright.bmp'; message=double(imread(file_name)); T=message; Mm=size(message,1); %Height Nm=size(message,2); %Width % perform 1-level DWT for the whole cover image [cA1,cH1,cV1,cD1] = dwt2(cover_object,'haar'); % determine the size of cA1 [RcA1 CcA1]=size(cA1) % perform 2-level DWT for cA1 [cA2,cH2,cV2,cD2] = dwt2(cA1,'haar'); % determine the size of cA2 [RcA2 CcA2]=size(cA2) % set the value of blocksize blocksize=4 % reshape the watermark to a vector message_vector=round(reshape(message,Mm*Nm,1)./256); W=message_vector; % determine maximum message size based on cA2, and blocksize max_message=RcA2*CcA2/(blocksize^2) % check that the message isn't too large for cover if (length(message) max_message) error('Message too large to fit in Cover Object') end %----------------------- process the image in blocks ---------------------- x=1; y=1; for (kk = 1:length(message_vector)) [cA2u cA2s cA2v]=svd(cA2(y:y+blocksize-1,x:x+blocksize-1)); % if message bit contains zero, modify S of the original image if (message_vector(kk) == 0) cA2s = cA2s*(1 + alpha); % otherwise mask is filled with zeros else cA2s=cA2s; end cA22(y:y+blocksize-1,x:x+blocksize-1)=cA2u*cA2s*cA2v; % move to next block of mask along x; If at end of row, move to next row if (x+blocksize) >= CcA2 x=1; y=y+blocksize; else x=x+blocksize; end end % perform IDWT CAA1 = idwt2(cA22,cH2,cV2,cD2,'haar',[RcA1,CcA1]); watermarked_image= idwt2(CAA1,cH1,cV1,cD1,'haar',[Mc,Nc]); % convert back to uint8 watermarked_image_uint8=uint8(watermarked_image); % write watermarked Image to file imwrite(watermarked_image_uint8,'dwt_watermarked.bmp','bmp'); % display watermarked image figure(1) imshow(watermarked_image_uint8,[]) title('Watermarked Image') %(2) ---------------------------------------------------------------------- %---------- Extract Watermark from attacked watermarked image ------------- %-------------------------------------------------------------------------- % read in the watermarked object file_name='dwt_watermarked.bmp'; watermarked_image=double(imread(file_name)); % determine size of watermarked image Mw=size(watermarked_image,1); %Height Nw=size(watermarked_image,2); %Width % perform 1-level DWT for the whole watermarked image [ca1,ch1,cv1,cd1] = dwt2(watermarked_image,'haar'); % determine the size of ca1 [Rca1 Cca1]=size(ca1); % perform 2-level DWT for ca1 [ca2,ch2,cv2,cd2] = dwt2(ca1,'haar'); % determine the size of ca2 [Rca2 Cca2]=size(ca2); % process the image in blocks % for each block get a bit for message x=1; y=1; for (kk = 1:length(message_vector)) % sets correlation to 1 when patterns are identical to avoid /0 errors % otherwise calcluate difference between the cover image and the % watermarked image [cA2u cA2s cA2v]=svd(cA2(y:y+blocksize-1,x:x+blocksize-1)); [ca2u1 ca2s1 ca2v1]=svd(ca2(y:y+blocksize-1,x:x+blocksize-1)); correlation(kk)=diag(ca2s1-cA2s)'*diag(ca2s1-cA2s)/(alpha*alpha)/(diag(cA2s)*diag(cA2s)); % move on to next block. At and of row move to next row if (x+blocksize) >= Cca2 x=1; y=y+blocksize; else x=x+blocksize; end end % if correlation exceeds average correlation correlation(kk)=correlation(kk)+mean(correlation(1:Mm*Nm)); for kk = 1:length(correlation) if (correlation(kk) > thresh*alpha);%thresh*mean(correlation(1:Mo*No))) message_vector(kk)=0; end end % reshape the message vector and display recovered watermark. figure(2) message=reshape(message_vector(1:Mm*Nm),Mm,Nm); imshow(message,[]) title('Recovered Watermark') % display processing time elapsed_time=cputime-start_time, please do help,its my graduation project and i have been trying this code for along time but failed miserable. Thanks in advance

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• c# login Screen Error

  - by Kumu

  The type or namespace name 'Login' could not be found (are you missing a using directive or an assembly reference?) This error displays according to the MainMenu of my system. The following code describes the MainMenu source code of my system. Login login; is the error place which system shows, using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace FootballLeague { public partial class MainMenu : Form { FootballLeagueDatabase footballLeagueDatabase; Game game; Team team; **Login login;** public MainMenu() { InitializeComponent(); changePanel(1); } public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) { InitializeComponent(); footballLeagueDatabase = footballLeagueDatabaseIn; } //FootballLeagueDatabase footballLeagueDatabase = new FootballLeagueDatabase(); private void Form_Loaded(object sender, EventArgs e) { } private void gameButton_Click(object sender, EventArgs e) { int option = 0; changePanel(option); } private void scoreboardButton_Click(object sender, EventArgs e) { int option = 1; changePanel(option); } private void changePanel(int optionIn) { gamePanel.Hide(); scoreboardPanel.Hide(); string title = "Football League System"; switch (optionIn) { case 0: gamePanel.Show(); this.Text = title + " - Game Menu"; break; case 1: scoreboardPanel.Show(); this.Text = title + " - Display Menu"; break; } } private void logoutButton_Click(object sender, EventArgs e) { login = new Login(); login.Show(); this.Hide(); } and I have the Form class called Login.cs and the following code displays that class. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace FootballLeagueSystem { public partial class Login : Form { MainMenu menu; public Login() { InitializeComponent(); } private void administratorLoginButton_Click(object sender, EventArgs e) { string username1 = "08247739"; string password1 = "08247739"; if ((userNameTxt.Text.Length) == 0) MessageBox.Show("Please enter your username!"); else if ((passwordTxt.Text.Length) == 0) MessageBox.Show("Please enter your password!"); else if (userNameTxt.Text.Equals("") || passwordTxt.Text.Equals("")) MessageBox.Show("Invalid Username or Password!"); else { if (this.userNameTxt.Text == username1 && this.passwordTxt.Text == password1) MessageBox.Show("Welcome Administrator!", "Administrator Login"); menu = new MainMenu(); menu.Show(); this.Hide(); } } private void managerLoginButton_Click(object sender, EventArgs e) { { string username2 = "1111"; string password2 = "1111"; if ((userNameTxt.Text.Length) == 0) MessageBox.Show("Please enter your username!"); else if ((passwordTxt.Text.Length) == 0) MessageBox.Show("Please enter your password!"); else if (userNameTxt.Text.Equals("") && passwordTxt.Text.Equals("")) MessageBox.Show("Invalid Username or Password!"); //menu = new MainMenu(); //menu.Hide(); //this.Close(); else { if (this.userNameTxt.Text == username2 && this.passwordTxt.Text == password2) MessageBox.Show("Welcome Manager!", "Manager Login"); menu = new MainMenu(); menu.Show(); //menu.HideTab(); this.Hide(); } } } private void cancelButton_Click(object sender, EventArgs e) { this.Close(); } } } Please can you someone explain me where is the error is?

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• Java: design problem with final-value and empty constructor

  - by HH

  $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; // Design Problem? // I feel the initialization problem is just due to bad style. InitInt(){} InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } } public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Partial Solutions and Suggestions use "this" to access methods in the class, instead of creating empty constructor change final to non-final with final field value: initialize all final values in every constructor remove the empty constructor, keep your code simple and clean

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• ArgumentOutOfRangeException at MySql execution. (MySqlConnector .NET)

  - by Lazlo

  I am getting this exception from a MySqlCommand.ExecuteNonQuery(): Index and length must refer to a location within the string. Parameter name: length The command text is as follows: INSERT INTO accounts (username, password, salt, pin, banned, staff, logged_in, points_a, points_b, points_c, birthday) VALUES ('adminb', 'aea785fbcac7f870769d30226ad55b1aab850fb0979ee00481a87bc846744a646a649d30bca5474b59e4292095c74fa47ae6b9b3a856beef332ff873474cc0d3', 'cb162ef55ff7c58c7cb9f2a580928679', '', '0, '0', '0', '0', '0', '0', '2010-04-18') Sorry for the long string, it is a SHA512 hash. I tried manually adding this data in the table from MySQL GUI tools, and it worked perfectly. I see no "out of range" problem in these strings. Does anybody see something wrong?

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• Sending lots of mails using SmtpClient (C#) takes very long after a while

  - by Lieven Cardoen

  I'm using this piece of code to send a mail: SmtpClient client = new SmtpClient(); client.Host = smtpServer; client.Send(mailMessage); If I trigger this code ten times/second, then after some hundred mails, sending a mail takes 10 seconds... Could there be a queue involved here?

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• JavaDB connection error (network protocol)

  - by oO

  I'm trying to connect to derby using this: dbProperties.put("create", "true"); dbProperties.put("dataEncryption", "true"); dbProperties.put("encryptionAlgorithm", "DES/CBC/NoPadding"); dbProperties.put("encryptionKey", "1234567890123456"); dbProperties.put("securityMechanism", ClientDataSource.STRONG_PASSWORD_SUBSTITUTE_SECURITY); // protocol is dbProperties.getProperty("derby.url", "jdbc:derby://localhost:1527/"); dbConnection = DriverManager.getConnection(protocol + dbName, dbProperties); but i get an error: A connection could not be established because the database name (...) is larger than the maximum length allowed by the network protocol. Is there a way to increase this length?

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• Configuring Postfix with other SMTP provider

  - by Eduard Luca

  I want to use SendGrid as my email sending service, but want to also use Postfix's internal queue mechanism to manage the emails sent through Sendgrid. So basically what I want to do is to configure Postfix to send emails through Sendgrid's SMTP, and I will configure my app to send the emails using the local Postfix. My question is, how can I configure Postfix to use an external SMTP? Looked here but didn't see anything useful.

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• Python list comprehension to return edge values of a list

  - by mvid

  If I have a list in python such as: stuff = [1, 2, 3, 4, 5, 6, 7, 8, 9] with length n (in this case 9) and I am interested in creating lists of length n/2 (in this case 4). I want all possible sets of n/2 values in the original list, for example: [1, 2, 3, 4], [2, 3, 4, 5], ..., [9, 1, 2, 3] is there some list comprehension code I could use to iterate through the list and retrieve all of those sublists? I don't care about the order of the values within the lists, I am just trying to find a clever method of generating the lists.

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• A couple questions using fwrite/fread with data structures

  - by Nazgulled

  Hi, I'm using fwrite() and fread() for the first time to write some data structures to disk and I have a couple of questions about best practices and proper ways of doing things. What I'm writing to disk (so I can later read it back) is all user profiles inserted in a Graph structure. Each graph vertex is of the following type: typedef struct sUserProfile { char name[NAME_SZ]; char address[ADDRESS_SZ]; int socialNumber; char password[PASSWORD_SZ]; HashTable *mailbox; short msgCount; } UserProfile; And this is how I'm currently writing all the profiles to disk: void ioWriteNetworkState(SocialNetwork *social) { Vertex *currPtr = social->usersNetwork->vertices; UserProfile *user; FILE *fp = fopen("save/profiles.dat", "w"); if(!fp) { perror("fopen"); exit(EXIT_FAILURE); } fwrite(&(social->usersCount), sizeof(int), 1, fp); while(currPtr) { user = (UserProfile*)currPtr->value; fwrite(&(user->socialNumber), sizeof(int), 1, fp); fwrite(user->name, sizeof(char)*strlen(user->name), 1, fp); fwrite(user->address, sizeof(char)*strlen(user->address), 1, fp); fwrite(user->password, sizeof(char)*strlen(user->password), 1, fp); fwrite(&(user->msgCount), sizeof(short), 1, fp); break; currPtr = currPtr->next; } fclose(fp); } Notes: The first fwrite() you see will write the total user count in the graph so I know how much data I need to read back. The break is there for testing purposes. There's thousands of users and I'm still experimenting with the code. My questions: After reading this I decided to use fwrite() on each element instead of writing the whole structure. I also avoid writing the pointer to to the mailbox as I don't need to save that pointer. So, is this the way to go? Multiple fwrite()'s instead of a global one for the whole structure? Isn't that slower? How do I read back this content? I know I have to use fread() but I don't know the size of the strings, cause I used strlen() to write them. I could write the output of strlen() before writing the string, but is there any better way without extra writes?

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• Error in unzipping a file from a python script running as daemon

  - by Fedrick

  I am getting an error whenever i try to run following unzip command from a python script which is running as a daemon Command : unzip abcd.zip /dev/null Error End-of-central-directory signature not found$ a zip file, or it constitutes one disk of a multi-part archive. In the latter case the central directory and zipfile comment will be found on the last disk(s) of this archive unzip: cannot find zipfile directory in one of abcd.zip$ abcd.zip.zip, and cannot find abcd.zip.ZIP, period. Could anyone help me in this regard? Thanks in advance.

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• how to read character behind some text

  - by klox

  this one a code for read two character behind text "KD-R411ED" var code = data[0].substr(data[0].length - 2); how to read ED character if text like KD-R411H2EDT? i want a new code can combine with code above..please help!! look this: $("#tags1").change(function() { var barcode; barCode=$("#tags1").val(); var data=barCode.split(" "); $("#tags1").val(data[0]); $("#tags2").val(data[1]); var code = data[0].substr(data[0].length - 2); // suggested by Jan Willem B if (code == 'UD') { $('#check1').attr('checked','checked'); } else { if (code == 'ED') { $('#check2').attr('checked','checked'); } }

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• memcpy(), what should the value of the size parameter be?

  - by Tomas

  Hi, I want to copy an int array to another int array. They use the same define for length so they'll always be of the same length. What are the pros/cons of the following two alternatives of the size parameter to memcpy()? memcpy(dst, src, ARRAY_LENGTH*sizeof(int)); or memcpy(dst, src, sizeof(dst); Will the second option always work? Regardless of the content? One thing that favors the last one is that if the array were to change, it'll be some house-keeping to update the memcpy()'s. Thanks

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• Exception design: Custom exceptions reading data from file?

  - by User

  I have a method that reads data from a comma separated text file and constructs a list of entity objects, let's say customers. So it reads for example, Name Age Weight Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I'm trying to figure out the best error handling design. For example, the text file might have character data in the Age field. Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there? (If you can point me to a good resource that would be good too)

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• C++: Implementing Named Pipes using the Win32 API

  - by Mike Pateras

  I'm trying to implement named pipes in C++, but either my reader isn't reading anything, or my writer isn't writing anything (or both). Here's my reader: int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); char data[1024]; DWORD numRead = 1; while (numRead >= 0) { ReadFile(pipe, data, 1024, &numRead, NULL); if (numRead > 0) cout << data; } return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } And here's my writer: int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); string message = "Hi"; WriteFile(pipe, message.c_str(), message.length() + 1, NULL, NULL); return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } Does that look right? numRead in the reader is always 0, for some reason, and it reads nothing but 1024 -54's (some weird I character). Solution: Reader (Server): while (true) { HANDLE pipe = CreateNamedPipe(GetPipeName(), PIPE_ACCESS_INBOUND | PIPE_ACCESS_OUTBOUND , PIPE_WAIT, 1, 1024, 1024, 120 * 1000, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout << "Error: " << GetLastError(); } char data[1024]; DWORD numRead; ConnectNamedPipe(pipe, NULL); ReadFile(pipe, data, 1024, &numRead, NULL); if (numRead > 0) cout << data << endl; CloseHandle(pipe); } Writer (client): HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout << "Error: " << GetLastError(); } string message = "Hi"; cout << message.length(); DWORD numWritten; WriteFile(pipe, message.c_str(), message.length(), &numWritten, NULL); return 0; The server blocks until it gets a connected client, reads what the client writes, and then sets itself up for a new connection, ad infinitum. Thanks for the help, all!

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• Fluent-NHibernate - Component property attributes ignored by Convention

  - by BobTodd

  I have a component with a number of properties that have various attributes Normally when these attributes are added to a plain old domain object they are picked up by my custom AttributeConventions. For the Component properties they are not. Is there some extra wiring needed for these? e.g. public class Component { [Length(Max=50)] public virtual string Name {get; set;} } public class MyClass { public virtual Component Component {get; set;} [Length(Max=50)] public virtual string Color {get; set;} } I get a table MyClass with columns Color & ComponentName Color is an nvarchar(50) whilst ComponentName is an nvarchar(255) (the default)

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• Shortest-path algorithms which use a space-time tradeoff?

  - by Chris Mounce

  I need to find shortest paths in an unweighted, undirected graph. There are algorithms which can find a shortest path between two nodes, but this can take time. There are also algorithms for computing shortest paths for all pairs of nodes in the graph, but storing such a lookup table would take lots of disk space. What I'm wondering: Is there an algorithm which offers a space-time tradeoff that's somewhere between these two extremes? In other words, is there a way to speed up a shortest-path search, while using less disk space than would be occupied by an all-pairs shortest-path table? I know there are ways to efficiently store lookup tables for this problem, and I already have a couple of ideas for speeding up shortest-path searches using precomputed data. But I don't want to reinvent the wheel if there's already some established algorithm that solves this problem.

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• Saving a huge dataset into SQL table in a XML column - MS SQL, C#.Net

  - by NLV

  Hello all I'm having a requirement where i've to save a dataset which has multiple tables in it in a sql table XML column by converting into an XML. The problem is that in some cases the dataset grows extremely huge and i get OutOfMemoryException. What i basically do is that i convert the dataset into an xml file and save it in the local disk and then load the XML again and send it as a stored procedure parameter. But when i write the dataset xml into the disk the file sizes over 700 Mb and when i load it in the XMLDocument object in memory i get OutOfMemoryException. How can get the dataset xml without saving it in a file and re-reading it again? Thank You NLV

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• Are there any free .NET OCR libraries that will perform OCR on an application window directly?

  - by Kelsey

  I am looking for a free .NET OCR library that will be able to do OCR on a given application window or even a image in memory (I can take a snapshot of the application window myself). I have looked at tessnet2 and MODI but both require an image located on disk. I need to use OCR because the application I am trying to write a script for does some wacky stuff that cannot be read using windows API and I need to scrape data from the screen. I have tested both of tessnet2 and MODI and they both can read the text mostly but because this has to run in an enviroment that will not be able to write to disk, I need it to be able to read directly from the applciation window or some type of memory stream. I am thinking OCR is my only soution but there could be other methods that I am not thinking of. Suggestions?

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• problems in trying ieee 802.15.4 working from msk

  - by asel

  Hi, i took a msk code from dsplog.com and tried to modify it to test the ieee 802.15.4. There are several links on that site for ieee 802.15.4. Currently I am getting simulated ber results all approximately same for all the cases of Eb_No values. Can you help me to find why? thanks in advance! clear PN = [ 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0; 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0; 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0; 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1; 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1; 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0; 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1; 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1; 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1; 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1; 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1; 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0; 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0; 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1; 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0; 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0; ]; N = 5*10^5; % number of bits or symbols fsHz = 1; % sampling period T = 4; % symbol duration Eb_N0_dB = [0:10]; % multiple Eb/N0 values ct = cos(pi*[-T:N*T-1]/(2*T)); st = sin(pi*[-T:N*T-1]/(2*T)); for ii = 1:length(Eb_N0_dB) tx = []; % MSK Transmitter ipBit = round(rand(1,N/32)*15); for k=1:length(ipBit) sym = ipBit(k); tx = [tx PN((sym+1),1:end)]; end ipMod = 2*tx - 1; % BPSK modulation 0 -> -1, 1 -> 1 ai = kron(ipMod(1:2:end),ones(1,2*T)); % even bits aq = kron(ipMod(2:2:end),ones(1,2*T)); % odd bits ai = [ai zeros(1,T) ]; % padding with zero to make the matrix dimension match aq = [zeros(1,T) aq ]; % adding delay of T for Q-arm % MSK transmit waveform xt = 1/sqrt(T)*[ai.*ct + j*aq.*st]; % Additive White Gaussian Noise nt = 1/sqrt(2)*[randn(1,N*T+T) + j*randn(1,N*T+T)]; % white gaussian noise, 0dB variance % Noise addition yt = xt + 10^(-Eb_N0_dB(ii)/20)*nt; % additive white gaussian noise % MSK receiver % multiplying with cosine and sine waveforms xE = conv(real(yt).*ct,ones(1,2*T)); xO = conv(imag(yt).*st,ones(1,2*T)); bHat = zeros(1,N); bHat(1:2:end) = xE(2*T+1:2*T:end-2*T); % even bits bHat(2:2:end) = xO(3*T+1:2*T:end-T); % odd bits result=zeros(16,1); chiplen=32; seqstart=1; recovered = []; while(seqstart<length(bHat)) A = bHat(seqstart:seqstart+(chiplen-1)); for j=1:16 B = PN(j,1:end); result(j)=sum(A.*B); end [value,index] = max(result); recovered = [recovered (index-1)]; seqstart = seqstart+chiplen; end; %# create binary string - the 4 forces at least 4 bits bstr1 = dec2bin(ipBit,4); bstr2 = dec2bin(recovered,4); %# convert back to numbers (reshape so that zeros are preserved) out1 = str2num(reshape(bstr1',[],1))'; out2 = str2num(reshape(bstr2',[],1))'; % counting the errors nErr(ii) = size(find([out1 - out2]),2); end nErr/(length(ipBit)*4) % simulated ber theoryBer = 0.5*erfc(sqrt(10.^(Eb_N0_dB/10))) % theoretical ber

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