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• Why is my mdadm raid-1 recovery so slow?

  - by dimmer

  On a system I'm running Ubuntu 10.04. My raid-1 restore started out fast but quickly became ridiculously slow (at this rate the restore will take 150 days!): dimmer@paimon:~$ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdc1[2] sdb1[1] 1953513408 blocks [2/1] [_U] [====>................] recovery = 24.4% (477497344/1953513408) finish=217368.0min speed=113K/sec unused devices: <none> Eventhough I have set the kernel variables to reasonably quick values: dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_min 1000000 dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_max 100000000 I am using 2 2.0TB Western Digital Hard Disks, WDC WD20EARS-00M and WDC WD20EARS-00J. I believe they have been partitioned such that their sectors are aligned. dimmer@paimon:/sys$ sudo parted /dev/sdb GNU Parted 2.2 Using /dev/sdb Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00M (scsi) Disk /dev/sdb: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 (parted) unit s (parted) p Number Start End Size File system Name Flags 1 2048s 3907028991s 3907026944s ext4 (parted) q dimmer@paimon:/sys$ sudo parted /dev/sdc GNU Parted 2.2 Using /dev/sdc Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00J (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/4096B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 I am beginning to think that I have a hardware problem, otherwise I can't imagine why the mdadm restore should be so slow. I have done a benchmark on /dev/sdc using Ubuntu's disk utility GUI app, and the results looked normal so I know that sdc has the capability to write faster than this. I also had the same problem on a similar WD drive that I RMAd because of bad sectors. I suppose it's possible they sent me a replacement with bad sectors too, although there are no SMART values showing them yet. Any ideas? Thanks. As requested, output of top sorted by cpu usage (notice there is ~0 cpu usage). iowait is also zero which seems strange: top - 11:35:13 up 2 days, 9:40, 3 users, load average: 2.87, 2.58, 2.30 Tasks: 142 total, 1 running, 141 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3096304k total, 1482164k used, 1614140k free, 617672k buffers Swap: 1526132k total, 0k used, 1526132k free, 535416k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 45 root 20 0 0 0 0 S 0 0.0 2:17.02 scsi_eh_0 1 root 20 0 2808 1752 1204 S 0 0.1 0:00.46 init 2 root 20 0 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/0 4 root 20 0 0 0 0 S 0 0.0 0:00.17 ksoftirqd/0 5 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/1 ... dmesg errors, definitely looking like hardware: [202884.000157] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [202884.007015] ata5.00: failed command: FLUSH CACHE EXT [202884.013728] ata5.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0 [202884.013730] res 40/00:00:ff:59:2e/00:00:35:00:00/e0 Emask 0x4 (timeout) [202884.033667] ata5.00: status: { DRDY } [202884.040329] ata5: hard resetting link [202889.400050] ata5: link is slow to respond, please be patient (ready=0) [202894.048087] ata5: COMRESET failed (errno=-16) [202894.054663] ata5: hard resetting link [202899.412049] ata5: link is slow to respond, please be patient (ready=0) [202904.060107] ata5: COMRESET failed (errno=-16) [202904.066646] ata5: hard resetting link [202905.840056] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [202905.849178] ata5.00: configured for UDMA/133 [202905.849188] ata5: EH complete [203899.000292] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [203899.007096] ata5.00: failed command: IDENTIFY DEVICE [203899.013841] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [203899.013843] res 40/00:00:ff:f9:f6/00:00:38:00:00/e0 Emask 0x4 (timeout) [203899.041232] ata5.00: status: { DRDY } [203899.048133] ata5: hard resetting link [203899.816134] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [203899.826062] ata5.00: configured for UDMA/133 [203899.826079] ata5: EH complete [204375.000200] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204375.007421] ata5.00: failed command: IDENTIFY DEVICE [204375.014799] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204375.014800] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204375.044374] ata5.00: status: { DRDY } [204375.051842] ata5: hard resetting link [204380.408049] ata5: link is slow to respond, please be patient (ready=0) [204384.440076] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204384.449938] ata5.00: configured for UDMA/133 [204384.449955] ata5: EH complete [204395.988135] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204395.988140] ata5.00: failed command: IDENTIFY DEVICE [204395.988147] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204395.988149] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204395.988151] ata5.00: status: { DRDY } [204395.988156] ata5: hard resetting link [204399.320075] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204399.330487] ata5.00: configured for UDMA/133 [204399.330503] ata5: EH complete

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• Parsing xml file that comes in as one object per line

  - by Casey

  I haven't been here in so long, I forgot my prior account! Anyways, I am working on parsing an xml document that comes in ugly. It is for banking statements. Each line is a <statement>all tags</statement>. Now, what I need to do is read this file in, and parse the XML document at the same time, while formatting it more human readable too. Point beeing, Original input looks like this: <statement><accountHeader><fiAddress></fiAddress><accountNumber></accountNumber><startDate>20140101</startDate><endDate>20140228</endDate><statementGroup>1</statementGroup><sortOption>0</sortOption><memberBranchCode>1</memberBranchCode><memberName></memberName><jointOwner1Name></jointOwner1Name><jointOwner2Name></jointOwner2Name></summary></statement> <statement><accountHeader><fiAddress></fiAddress><accountNumber></accountNumber><startDate>20140101</startDate><endDate>20140228</endDate><statementGroup>1</statementGroup><sortOption>0</sortOption><memberBranchCode>1</memberBranchCode><memberName></memberName><jointOwner1Name></jointOwner1Name><jointOwner2Name></jointOwner2Name></summary></statement> <statement><accountHeader><fiAddress></fiAddress><accountNumber></accountNumber><startDate>20140101</startDate><endDate>20140228</endDate><statementGroup>1</statementGroup><sortOption>0</sortOption><memberBranchCode>1</memberBranchCode><memberName></memberName><jointOwner1Name></jointOwner1Name><jointOwner2Name></jointOwner2Name></summary></statement> I need the final output to be as follows: <statement> <name></name> <address></address> </statement> This is fine and dandy. I am using the following "very slow considering 5.1 million lines, 254k data file, and about 60k statements takes around 8 minutes". foreach(String item in lines) { XElement xElement = XElement.Parse(item); sr.WriteLine(xElement.ToString().Trim()); } Then when the file is formatted this is what sucks. I need to check every single tag in transaction elements, and if a tag is missing that could be there, I have to fill it in. Our designer software will default prior values in if a tag is possible, and the current objects does not have. It defaults in the value of a prior one that was not Null. "I know, and they swear up and down it is not a bug... ok?" So, that is also taking about 5 to 10 minutes. I need to break all this down, and find a faster method for working with the initial XML. This is a preprocess action, and cannot take that long if not necessary. It just seems redundant. Is there a better way to parse the XML, or is this the best I can do? I parse the XML, write to a temp file, and then read that file in, to the output file inserting the missing tags. 2 IO runs for one process. Yuck.

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• Picking good first estimates for Goldschmidt division

  - by Mads Elvheim

  I'm calculating fixedpoint reciprocals in Q22.10 with Goldschmidt division for use in my software rasterizer on ARM. This is done by just setting the nominator to 1, i.e the nominator becomes the scalar on the first iteration. To be honest, I'm kind of following the wikipedia algorithm blindly here. The article says that if the denominator is scaled in the half-open range (0.5, 1.0], a good first estimate can be based on the denominator alone: Let F be the estimated scalar and D be the denominator, then F = 2 - D. But when doing this, I lose a lot of precision. Say if I want to find the reciprocal of 512.00002f. In order to scale the number down, I lose 10 bits of precision in the fraction part, which is shifted out. So, my questions are: Is there a way to pick a better estimate which does not require normalization? Also, is it possible to pre-calculate the first estimates so the series converges faster? Right now, it converges after the 4th iteration on average. On ARM this is about ~50 cycles worst case, and that's not taking emulation of clz/bsr into account, nor memory lookups. Here is my testcase. Note: The software implementation of clz on line 13 is from my post here. You can replace it with an intrinsic if you want. #include <stdio.h> #include <stdint.h> const unsigned int BASE = 22ULL; static unsigned int divfp(unsigned int val, int* iter) { /* Nominator, denominator, estimate scalar and previous denominator */ unsigned long long N,D,F, DPREV; int bitpos; *iter = 1; D = val; /* Get the shift amount + is right-shift, - is left-shift. */ bitpos = 31 - clz(val) - BASE; /* Normalize into the half-range (0.5, 1.0] */ if(0 < bitpos) D >>= bitpos; else D <<= (-bitpos); /* (FNi / FDi) == (FN(i+1) / FD(i+1)) */ /* F = 2 - D */ F = (2ULL<<BASE) - D; /* N = F for the first iteration, because the nominator is simply 1. So don't waste a 64-bit UMULL on a multiply with 1 */ N = F; D = ((unsigned long long)D*F)>>BASE; while(1){ DPREV = D; F = (2<<(BASE)) - D; D = ((unsigned long long)D*F)>>BASE; /* Bail when we get the same value for two denominators in a row. This means that the error is too small to make any further progress. */ if(D == DPREV) break; N = ((unsigned long long)N*F)>>BASE; *iter = *iter + 1; } if(0 < bitpos) N >>= bitpos; else N <<= (-bitpos); return N; } int main(int argc, char* argv[]) { double fv, fa; int iter; unsigned int D, result; sscanf(argv[1], "%lf", &fv); D = fv*(double)(1<<BASE); result = divfp(D, &iter); fa = (double)result / (double)(1UL << BASE); printf("Value: %8.8lf 1/value: %8.8lf FP value: 0x%.8X\n", fv, fa, result); printf("iteration: %d\n",iter); return 0; }

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• Modern alternatives to Java

  - by Ralph

  I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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• Limiting TCP sends with a "to-be-sent" queue and other design issues.

  - by Poni

  Hello all! This question is the result of two other questions I've asked in the last few days. I'm creating a new question because I think it's related to the "next step" in my understanding of how to control the flow of my send/receive, something I didn't get a full answer to yet. The other related questions are: http://stackoverflow.com/questions/3028376/an-iocp-documentation-interpretation-question-buffer-ownership-ambiguity http://stackoverflow.com/questions/3028998/non-blocking-tcp-buffer-issues In summary, I'm using Windows I/O Completion Ports. I have several threads that process notifications from the completion port. I believe the question is platform-independent and would have the same answer as if to do the same thing on a *nix, *BSD, Solaris system. So, I need to have my own flow control system. Fine. So I send send and send, a lot. How do I know when to start queueing the sends, as the receiver side is limited to X amount? Let's take an example (closest thing to my question): FTP protocol. I have two servers; One is on a 100Mb link and the other is on a 10Mb link. I order the 100Mb one to send to the other one (the 10Mb linked one) a 1GB file. It finishes with an average transfer rate of 1.25MB/s. How did the sender (the 100Mb linked one) knew when to hold the sending, so the slower one wouldn't be flooded? Another way to ask this: Can I get a "hold-your-sendings" notification from the remote side? Is it built-in in TCP or the so called "reliable network protocol" needs me to do so? Again, I have a loop with many sends to a remote server, and at some point, within that loop I'll have to determine if I should queue that send or I can pass it on to the transport layer (TCP). How do I do that? What would you do? Of course that when I get a completion notification from IOCP that the send was done I'll issue other pending sends, that's clear. Another design question related to this: Since I am to use a custom buffers with a send queue, and these buffers are being freed to be reused (thus not using the "delete" keyword) when a "send-done" notification has been arrived, I'll have to use a mutual exlusion on that buffer pool. Using a mutex slows things down, so I've been thinking; Why not have each thread have its own buffers pool, thus accessing it , at least when getting the required buffers for a send operation, will require no mutex, because it belongs to that thread only. The buffers pool is located at the thread local storage (TLS) level. No mutual pool implies no lock needed, implies faster operations BUT also implies more memory used by the app, because even if one thread already allocated 1000 buffers, the other one that is sending right now and need 1000 buffers to send something will need to allocated these to its own. This is a long question and I hope none got hurt (: Thank you all!

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• Change ListView background - strage behaviour

  - by Beasly

  Hi again, I have a problem with changing the background of a view in a ListView. What I need: Change the background image of a row onClick() What actually happens: The background gets changed (selected) after pressing e.g. the first entry. But after scrolling down the 8th entry is selected too. Scroll back to the top the first isn't selected anymore. The second entry is selected now. Continue scrolling and it continues jumping... What i'm dong in the Code: I have channels, and onClick() I toggle an attribute of channel boolean selected and then I change the background. I'm doing this only onClick() thats why I don't get why it's actuelly happening on other entries too. One thing I notices is: It seems to be only the "drawing"-part because the item which get selected "by it self" has still the selected value on false I think it seems to have something to do with the reuse of the views in the custom ListAdapters getView(...) Code of onClick() in ListActivity: @Override protected ViewHolder createHolder(View v) { // createHolder will be called only as long, as the ListView is not // filled TextView title = (TextView) v .findViewById(R.id.tv_title_channel_list_adapter); TextView content = (TextView) v .findViewById(R.id.tv_content_channel_list_adapter); ImageView icon = (ImageView) v .findViewById(R.id.icon_channel_list_adapter); if (title == null || content == null || icon == null) { Log.e("ERROR on findViewById", "Couldn't find Title, Content or Icon"); } ViewHolder mvh = new MyViewHolder(title, content, icon); // We make the views become clickable // so, it is not necessary to use the android:clickable attribute in // XML v.setOnClickListener(new ChannelListAdapter.OnClickListener(mvh) { public void onClick(View v, ViewHolder viewHolder) { // we toggle the enabled state and also switch the the // background MyViewHolder mvh = (MyViewHolder) viewHolder; Channel ch = (Channel) mvh.data; ch.setSelected(!ch.getSelected()); // toggle if (ch.getSelected()) { v.setBackgroundResource(R.drawable.row_blue_selected); } else { v.setBackgroundResource(R.drawable.row_blue); } // TESTING Log.d("onClick() Channel", "onClick() Channel: " + ch.getTitle() + " selected: " + ch.getSelected()); } }); return mvh; } Code of getView(...): @Override public View getView(int position, View view, ViewGroup parent) { ViewHolder holder; // When view is not null, we can reuse it directly, there is no need // to reinflate it. // We only inflate a new View when the view supplied by ListView is // null. if (view == null) { view = mInflater.inflate(mViewId, null); // call own implementation holder = createHolder(view); // TEST // we set the holder as tag view.setTag(holder); } else { // get holder back...much faster than inflate holder = (ViewHolder) view.getTag(); } // we must update the object's reference holder.data = getItem(position); // call the own implementation bindHolder(holder); return view; } I really would appreciate any idea how to solve this! :) If more information is needed please tell me. Thanks in advance!

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• Join and sum not compatible matrices through data.table

  - by leodido

  My goal is to "sum" two not compatible matrices (matrices with different dimensions) using (and preserving) row and column names. I've figured this approach: convert the matrices to data.table objects, join them and then sum columns vectors. An example: > M1 1 3 4 5 7 8 1 0 0 1 0 0 0 3 0 0 0 0 0 0 4 1 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 > M2 1 3 4 5 8 1 0 0 1 0 0 3 0 0 0 0 0 4 1 0 0 0 0 5 0 0 0 0 0 8 0 0 0 0 0 > M1 %ms% M2 1 3 4 5 7 8 1 0 0 2 0 0 0 3 0 0 0 0 0 0 4 2 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 This is my code: M1 <- matrix(c(0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0), byrow = TRUE, ncol = 6) colnames(M1) <- c(1,3,4,5,7,8) M2 <- matrix(c(0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0), byrow = TRUE, ncol = 5) colnames(M2) <- c(1,3,4,5,8) # to data.table objects DT1 <- data.table(M1, keep.rownames = TRUE, key = "rn") DT2 <- data.table(M2, keep.rownames = TRUE, key = "rn") # join and sum of common columns if (nrow(DT1) > nrow(DT2)) { A <- DT2[DT1, roll = TRUE] A[, list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1), by = rn] } That outputs: rn X1 X3 X4 X5 X7 X8 1: 1 0 0 2 0 0 0 2: 3 0 0 0 0 0 0 3: 4 2 0 0 0 0 0 4: 5 0 0 0 0 0 0 5: 7 0 0 0 0 1 0 6: 8 0 0 0 0 0 0 Then I can convert back this data.table to a matrix and fix row and column names. The questions are: how to generalize this procedure? I need a way to automatically create list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1) because i want to apply this function to matrices which dimensions (and row/columns names) are not known in advance. In summary I need a merge procedure that behaves as described. there are other strategies/implementations that achieve the same goal that are, at the same time, faster and generalized? (hoping that some data.table monster help me) to what kind of join (inner, outer, etc. etc.) is assimilable this procedure? Thanks in advance. p.s.: I'm using data.table version 1.8.2 EDIT - SOLUTIONS @Aaron solution. No external libraries, only base R. It works also on list of matrices. add_matrices_1 <- function(...) { a <- list(...) cols <- sort(unique(unlist(lapply(a, colnames)))) rows <- sort(unique(unlist(lapply(a, rownames)))) out <- array(0, dim = c(length(rows), length(cols)), dimnames = list(rows,cols)) for (m in a) out[rownames(m), colnames(m)] <- out[rownames(m), colnames(m)] + m out } @MadScone solution. Used reshape2 package. It works only on two matrices per call. add_matrices_2 <- function(m1, m2) { m <- acast(rbind(melt(M1), melt(M2)), Var1~Var2, fun.aggregate = sum) mn <- unique(colnames(m1), colnames(m2)) rownames(m) <- mn colnames(m) <- mn m } BENCHMARK (100 runs with microbenchmark package) Unit: microseconds expr min lq median uq max 1 add_matrices_1 196.009 257.5865 282.027 291.2735 549.397 2 add_matrices_2 13737.851 14697.9790 14864.778 16285.7650 25567.448 No need to comment the benchmark: @Aaron solution wins. I'll continue to investigate a similar solution for data.table objects. I'll add other solutions eventually reported or discovered.

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• Parallel processing via multithreading in Java

  - by Robz

  There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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• how can udp data can passed through RS232 in ansi c?

  - by moon

  i want to transmit and receive data on RS232 using udp and i want to know about techniques which allow me to transmit and receive data on a faster rate and also no lose of data is there? thanx in advance. i have tried but need improvements if possible #include <stdio.h> #include <dos.h> #include<string.h> #include<conio.h> #include<iostream.h> #include<stdlib.h> #define PORT1 0x3f8 void main() { int c,ch,choice,i,a=0; char filename[30],filename2[30],buf; FILE *in,*out; clrscr(); while(1){ outportb(PORT1+0,0x03); outportb(PORT1+1,0); outportb(PORT1+3,0x03); outportb(PORT1+2,0xc7); outportb(PORT1+4,0x0b); cout<<"\n==============================================================="; cout<<"\n\t*****Serial Communication By BADR-U-ZAMAN******\nCommunication between two computers By serial port"; cout<<"\nPlease select\n[1]\tFor sending file \n[2]\tFor receiving file \n[3]\tTo exit\n"; cout<<"=================================================================\n"; cin>>choice; if(choice==1) { strcpy(filename,"C:\\TC\\BIN\\badr.cpp"); cout<<filename; for(i=0;i<=strlen(filename);i++) outportb(PORT1,filename[i]); in=fopen(filename,"r"); if (in==NULL) { cout<<"cannot open a file"; a=1; } if(a!=1) cout<<"\n\nFile sending.....\n\n"; while(!feof(in)) { buf=fgetc(in); cout<<buf; outportb(PORT1,buf); delay(5); } } else { if(choice==3) exit(0); i=0; buf='a'; while(buf!=NULL) { c=inportb(PORT1+5); if(c&1) { buf=inportb(PORT1); filename2[i]=buf; i++; } } out=fopen(filename2,"t"); cout<<"\n Filename received:"<<filename[2]; cout<<"\nReading from the port..."; cout<<"writing to file"<<filename2; do { c=inportb(PORT1+5); if(c&1) { buf=inportb(PORT1); cout<<buf; fputc(buf,out); delay(5); } if(kbhit()) { ch=getch(); } }while(ch!=27); } getch(); } }

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• PostgreSQL triggers and passing parameters

  - by iandouglas

  This is a multi-part question. I have a table similar to this: CREATE TABLE sales_data ( Company character(50), Contract character(50), top_revenue_sum integer, top_revenue_sales integer, last_sale timestamp) ; I'd like to create a trigger for new inserts into this table, something like this: CREATE OR REPLACE FUNCTION add_contract() RETURNS VOID DECLARE myCompany character(50), myContract character(50), BEGIN myCompany = TG_ARGV[0]; myContract = TG_ARGV[1]; IF (TG_OP = 'INSERT') THEN EXECUTE 'CREATE TABLE salesdata_' || $myCompany || '_' || $myContract || ' ( sale_amount integer, updated TIMESTAMP not null, some_data varchar(32), country varchar(2) ) ;' EXECUTE 'CREATE TRIGGER update_sales_data BEFORE INSERT OR DELETE ON salesdata_' || $myCompany || '_' || $myContract || ' FOR EACH ROW EXECUTE update_sales_data( ' || $myCompany || ',' || $myContract || ', revenue);' ; END IF; END; $add_contract$ LANGUAGE plpgsql; CREATE TRIGGER add_contract AFTER INSERT ON sales_data FOR EACH ROW EXECUTE add_contract() ; Basically, every time I insert a new row into sales_data, I want to generate a new table where the name of the table will be defined as something like "salesdata_Company_Contract" So my first question is how can I pass the Company and Contract data to the trigger so it can be passed to the add_contract() stored procedure? From my stored procedure, you'll see that I also want to update the original sales_data table whenever new data is inserted into the salesdata_Company_Contract table. This trigger will do something like this: CREATE OR REPLACE FUNCTION update_sales_data() RETURNS trigger as $update_sales_data$ DECLARE myCompany character(50) NOT NULL, myContract character(50) NOT NULL, myRevenue integer NOT NULL BEGIN myCompany = TG_ARGV[0] ; myContract = TG_ARGV[1] ; myRevenue = TG_ARGV[2] ; IF (TG_OP = 'INSERT') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales + 1, top_revenue_sum = top_revenue_sum + $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; ELSIF (TG_OP = 'DELETE') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales - 1, top_revenue_sum = top_revenue_sum - $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; END IF; END; $update_sales_data$ LANGUAGE plpgsql; This will, of course, require that I pass several parameters around within these stored procedures and triggers, and I'm not sure (a) if this is even possible, or (b) practical, or (c) best practice and we should just put this logic into our other software instead of asking the database to do this work for us. To keep our table sizes down, as we'll have hundreds of thousands of transactions per day, we've decided to partition our data using the Company and Contract strings as part of the table names themselves so they're all very small in size; file IO for us is faster and we felt we'd get better performance. Thanks for any thoughts or direction. My thinking, now that I've written all of this out, is that maybe we need to write stored procedures where we pass our insert data as parameters, and call that from our other software, and have the stored procedure do the insert into "sales_data" then create the other table. Then, have a second stored procedure to insert new data into the salesdata_Company_Contract tables, where the table name is passed to the stored proc as a parameter, and again have that stored proc do the insert, then update the main sales_data table afterward. What approach would you take?

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• Various problems with software raid1 array built with Samsung 840 Pro SSDs

  - by Andy B

  I am bringing to ServerFault a problem that is tormenting me for 6+ months. I have a CentOS 6 (64bit) server with an md software raid-1 array with 2 x Samsung 840 Pro SSDs (512GB). Problems: Serious write speed problems: root [~]# time dd if=arch.tar.gz of=test4 bs=2M oflag=sync 146+1 records in 146+1 records out 307191761 bytes (307 MB) copied, 23.6788 s, 13.0 MB/s real 0m23.680s user 0m0.000s sys 0m0.932s When doing the above (or any other larger copy) the load spikes to unbelievable values (even over 100) going up from ~ 1. When doing the above I've also noticed very weird iostat results: Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 1589.50 0.00 54.00 0.00 13148.00 243.48 0.60 11.17 0.46 2.50 sdb 0.00 1627.50 0.00 16.50 0.00 9524.00 577.21 144.25 1439.33 60.61 100.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 0.00 1602.00 0.00 12816.00 8.00 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 And it keeps it this way until it actually writes the file to the device (out from swap/cache/memory). The problem is that the second SSD in the array has svctm and await roughly 100 times larger than the second. For some reason the wear is different between the 2 members of the array root [~]# smartctl --attributes /dev/sda | grep -i wear 177 Wear_Leveling_Count 0x0013 094% 094 000 Pre-fail Always - 180 root [~]# smartctl --attributes /dev/sdb | grep -i wear 177 Wear_Leveling_Count 0x0013 070% 070 000 Pre-fail Always - 1005 The first SSD has a wear of 6% while the second SSD has a wear of 30%!! It's like the second SSD in the array works at least 5 times as hard as the first one as proven by the first iteration of iostat (the averages since reboot): Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 10.44 51.06 790.39 125.41 8803.98 1633.11 11.40 0.33 0.37 0.06 5.64 sdb 9.53 58.35 322.37 118.11 4835.59 1633.11 14.69 0.33 0.76 0.29 12.97 md1 0.00 0.00 1.88 1.33 15.07 10.68 8.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 1109.02 173.12 10881.59 1620.39 9.75 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.41 0.01 3.10 0.02 7.42 0.00 0.00 0.00 0.00 What I've tried: I've updated the firmware to DXM05B0Q (following reports of dramatic improvements for 840Ps after this update). I have looked for "hard resetting link" in dmesg to check for cable/backplane issues but nothing. I have checked the alignment and I believe they are aligned correctly (1MB boundary, listing below) I have checked /proc/mdstat and the array is Optimal (second listing below). root [~]# fdisk -ul /dev/sda Disk /dev/sda: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00026d59 Device Boot Start End Blocks Id System /dev/sda1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sda2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sda3 4605952 814106623 404750336 fd Linux raid autodetect root [~]# fdisk -ul /dev/sdb Disk /dev/sdb: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0003dede Device Boot Start End Blocks Id System /dev/sdb1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sdb3 4605952 814106623 404750336 fd Linux raid autodetect /proc/mdstat root # cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb2[1] sda2[0] 204736 blocks super 1.0 [2/2] [UU] md2 : active raid1 sdb3[1] sda3[0] 404750144 blocks super 1.0 [2/2] [UU] md1 : active raid1 sdb1[1] sda1[0] 2096064 blocks super 1.1 [2/2] [UU] unused devices: Running a read test with hdparm root [~]# hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 664 MB in 3.00 seconds = 221.33 MB/sec root [~]# hdparm -t /dev/sdb /dev/sdb: Timing buffered disk reads: 288 MB in 3.01 seconds = 95.77 MB/sec But look what happens if I add --direct root [~]# hdparm --direct -t /dev/sda /dev/sda: Timing O_DIRECT disk reads: 788 MB in 3.01 seconds = 262.08 MB/sec root [~]# hdparm --direct -t /dev/sdb /dev/sdb: Timing O_DIRECT disk reads: 534 MB in 3.02 seconds = 176.90 MB/sec Both tests increase but /dev/sdb doubles while /dev/sda increases maybe 20%. I just don't know what to make of this. As suggested by Mr. Wagner I've done another read test with dd this time and it confirms the hdparm test: root [/home2]# dd if=/dev/sda of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 38.0855 s, 282 MB/s root [/home2]# dd if=/dev/sdb of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 115.24 s, 93.2 MB/s So sda is 3 times faster than sdb. Or maybe sdb is doing also something else besides what sda does. Is there some way to find out if sdb is doing more than what sda does? UPDATE Again, as suggested by Mr. Wagner, I have swapped the 2 SSDs. And as he thought it would happen, the problem moved from sdb to sda. So I guess I'll RMA one of the SSDs. I wonder if the cage might be problematic. What is wrong with this array? Please help!

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• Performance issues with jms and spring integration. What is wrong with the following configuration?

  - by user358448

  I have a jms producer, which generates many messages per second, which are sent to amq persistent queue and are consumed by single consumer, which needs to process them sequentially. But it seems that the producer is much faster than the consumer and i am having performance and memory problems. Messages are fetched very very slowly and the consuming seems to happen on intervals (the consumer "asks" for messages in polling fashion, which is strange?!) Basically everything happens with spring integration. Here is the configuration at the producer side. First stake messages come in stakesInMemoryChannel, from there, they are filtered throw the filteredStakesChannel and from there they are going into the jms queue (using executor so the sending will happen in separate thread) <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <int:channel id="stakesInMemoryChannel" /> <int:channel id="filteredStakesChannel" > <int:dispatcher task-executor="taskExecutor"/> </int:channel> <bean id="stakeFilterService" class="cayetano.games.stake.StakeFilterService"/> <int:filter input-channel="stakesInMemoryChannel" output-channel="filteredStakesChannel" throw-exception-on-rejection="false" expression="true"/> <jms:outbound-channel-adapter channel="filteredStakesChannel" destination="stakesQueue" delivery-persistent="true" explicit-qos-enabled="true" /> <task:executor id="taskExecutor" pool-size="100" /> The other application is consuming the messages like this... The messages come in stakesInputChannel from the jms stakesQueue, after that they are routed to 2 separate channels, one persists the message and the other do some other stuff, lets call it "processing". <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <jms:message-driven-channel-adapter channel="stakesInputChannel" destination="stakesQueue" acknowledge="auto" concurrent-consumers="1" max-concurrent-consumers="1" /> <int:publish-subscribe-channel id="stakesInputChannel" /> <int:channel id="persistStakesChannel" /> <int:channel id="processStakesChannel" /> <int:recipient-list-router id="customRouter" input-channel="stakesInputChannel" timeout="3000" ignore-send-failures="true" apply-sequence="true" > <int:recipient channel="persistStakesChannel"/> <int:recipient channel="processStakesChannel"/> </int:recipient-list-router> <bean id="prefetchPolicy" class="org.apache.activemq.ActiveMQPrefetchPolicy"> <property name="queuePrefetch" value="${jms.broker.prefetch.policy}" /> </bean> <bean id="connectionFactory" class="org.springframework.jms.connection.CachingConnectionFactory"> <property name="targetConnectionFactory"> <bean class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="${jms.broker.url}" /> <property name="prefetchPolicy" ref="prefetchPolicy" /> <property name="optimizeAcknowledge" value="true" /> <property name="useAsyncSend" value="true" /> </bean> </property> <property name="sessionCacheSize" value="10"/> <property name="cacheProducers" value="false"/> </bean>

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• Why don't I just build the whole web app in Javascript and Javascript HTML Templates?

  - by viatropos

  I'm getting to the point on an app where I need to start caching things, and it got me thinking... In some parts of the app, I render table rows (jqGrid, slickgrid, etc.) or fancy div rows (like in the New Twitter) by grabbing pure JSON and running it through something like Mustache, jquery.tmpl, etc. In other parts of the app, I just render the info in pure HTML (server-side HAML templates), and if there's searching/paginating, I just go to a new URL and load a new HTML page. Now the problem is in caching and maintainability. On one hand I'm thinking, if everything was built using Javascript HTML Templates, then my app would serve just an HTML layout/shell, and a bunch of JSON. If you look at the Facebook and Twitter HTML source, that's basically what they're doing (95% json/javascript, 5% html). This would make it so my app only needed to cache JSON (pages, actions, and/or records). Which means you'd hit the cache no matter if you were some remote api developer accessing a JSON api, or the strait web app. That is, I don't need 2 caches, one for the JSON, one for the HTML. That seems like it'd cut my cache store down in half, and streamline things a little bit. On the other hand, I'm thinking, from what I've seen/experienced, generating static HTML server-side, and caching that, seems to be much better performance wise cross-browser; you get the graphics instantly and don't have to wait that split-second for javascript to render it. StackOverflow seems to do everything in plain HTML, and you can tell... everything appears at once. Notice how though on twitter.com, the page is blank for .5-1 seconds, and the page chunks in: the javascript has to render the json. The downside with this is that, for anything dynamic (like endless scrolling, or grids), I'd have to create javascript templates anyway... so now I have server-side HAML templates, client-side javascript templates, and a lot more to cache. My question is, is there any consensus on how to approach this? What are the benefits and drawbacks from your experience of mixing the two versus going 100% with one over the other? Update: Some reasons that factor into why I haven't yet made the decision to go with 100% javascript templating are: Performance. Haven't formally tested, but from what I've seen, raw html renders faster and more fluidly than javascript-generated html cross-browser. Plus, I'm not sure how mobile devices handle dynamic html performance-wise. Testing. I have a lot of integration tests that work well with static HTML, so switching to javascript-only would require 1) more focused pure-javascript testing (jasmine), and 2) integrating javascript into capybara integration tests. This is just a matter of time and work, but it's probably significant. Maintenance. Getting rid of HAML. I love HAML, it's so easy to write, it prints pretty HTML... It makes code clean, it makes maintenance easy. Going with javascript, there's nothing as concise. SEO. I know google handles the ajax /#!/path, but haven't grasped how this will affect other search engines and how older browsers handle it. Seems like it'd require a significant setup.

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• Nginx + PHP-FPM on Centos 6.5 gives me 502 Bad Gateway (fpm error: unable to read what child say: Bad file descriptor)

  - by Latheesan Kanes

  I am setting up a standard LEMP stack. My current setup is giving me the following error: 502 Bad Gateway This is what is currently installed on my server: Here's the configurations I've created/updated so far, can some one take a look at the following and see where the error might be? I've already checked my logs, there's nothing in there (http://i.imgur.com/iRq3ksb.png). And I saw the following in /var/log/php-fpm/error.log file. sidenote: both the nginx and php-fpm has been configured to run under a local account called www-data and the following folders exits on the server nginx.conf global nginx configuration user www-data; worker_processes 6; worker_rlimit_nofile 100000; error_log /var/log/nginx/error.log crit; pid /var/run/nginx.pid; events { worker_connections 2048; use epoll; multi_accept on; } http { include /etc/nginx/mime.types; default_type application/octet-stream; # cache informations about FDs, frequently accessed files can boost performance open_file_cache max=200000 inactive=20s; open_file_cache_valid 30s; open_file_cache_min_uses 2; open_file_cache_errors on; # to boost IO on HDD we can disable access logs access_log off; # copies data between one FD and other from within the kernel # faster then read() + write() sendfile on; # send headers in one peace, its better then sending them one by one tcp_nopush on; # don't buffer data sent, good for small data bursts in real time tcp_nodelay on; # server will close connection after this time keepalive_timeout 60; # number of requests client can make over keep-alive -- for testing keepalive_requests 100000; # allow the server to close connection on non responding client, this will free up memory reset_timedout_connection on; # request timed out -- default 60 client_body_timeout 60; # if client stop responding, free up memory -- default 60 send_timeout 60; # reduce the data that needs to be sent over network gzip on; gzip_min_length 10240; gzip_proxied expired no-cache no-store private auth; gzip_types text/plain text/css text/xml text/javascript application/x-javascript application/xml; gzip_disable "MSIE [1-6]\."; # Load vHosts include /etc/nginx/conf.d/*.conf; } conf.d/www.domain.com.conf my vhost entry ## Nginx php-fpm Upstream upstream wwwdomaincom { server unix:/var/run/php-fcgi-www-data.sock; } ## Global Config client_max_body_size 10M; server_names_hash_bucket_size 64; ## Web Server Config server { ## Server Info listen 80; server_name domain.com *.domain.com; root /home/www-data/public_html; index index.html index.php; ## Error log error_log /home/www-data/logs/nginx-errors.log; ## DocumentRoot setup location / { try_files $uri $uri/ @handler; expires 30d; } ## These locations would be hidden by .htaccess normally #location /app/ { deny all; } ## Disable .htaccess and other hidden files location /. { return 404; } ## Magento uses a common front handler location @handler { rewrite / /index.php; } ## Forward paths like /js/index.php/x.js to relevant handler location ~ .php/ { rewrite ^(.*.php)/ $1 last; } ## Execute PHP scripts location ~ \.php$ { try_files $uri =404; expires off; fastcgi_read_timeout 900; fastcgi_pass wwwdomaincom; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } ## GZip Compression gzip on; gzip_comp_level 8; gzip_min_length 1000; gzip_proxied any; gzip_types text/plain application/xml text/css text/js application/x-javascript; } /etc/php-fpm.d/www-data.conf my php-fpm pool config ## Nginx php-fpm Upstream upstream wwwdomaincom { server unix:/var/run/php-fcgi-www-data.sock; } ## Global Config client_max_body_size 10M; server_names_hash_bucket_size 64; ## Web Server Config server { ## Server Info listen 80; server_name domain.com *.domain.com; root /home/www-data/public_html; index index.html index.php; ## Error log error_log /home/www-data/logs/nginx-errors.log; ## DocumentRoot setup location / { try_files $uri $uri/ @handler; expires 30d; } ## These locations would be hidden by .htaccess normally #location /app/ { deny all; } ## Disable .htaccess and other hidden files location /. { return 404; } ## Magento uses a common front handler location @handler { rewrite / /index.php; } ## Forward paths like /js/index.php/x.js to relevant handler location ~ .php/ { rewrite ^(.*.php)/ $1 last; } ## Execute PHP scripts location ~ \.php$ { try_files $uri =404; expires off; fastcgi_read_timeout 900; fastcgi_pass wwwdomaincom; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } ## GZip Compression gzip on; gzip_comp_level 8; gzip_min_length 1000; gzip_proxied any; gzip_types text/plain application/xml text/css text/js application/x-javascript; } I've got a file in /home/www-data/public_html/index.php with the code <?php phpinfo(); ?> (file uploaded as user www-data).

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• extensible database design: automatic ALTER TABLE or serialize() field BLOB ?

  - by mario

  I want an adaptable database scheme. But still use a simple table data gateway in my application, where I just pass an $data[] array for storing. The basic columns are settled in the initial table scheme. There will however arise a couple of meta fields later (ca 10-20). I want some flexibility there and not adapt the database manually each time, or -worse- change the application logic just because of new fields. So now there are two options which seem workable yet not overkill. But I'm not sure about the scalability or database drawbacks. (1) Automatic ALTER TABLE. Whenever the $data array is to be saved, the keys are compared against the current database columns. New columns get defined before the $data is INSERTed into the table. Actually seems simple enough in test code: function save($data, $table="forum") { // columns if ($new_fields = array_diff(array_keys($data), known_fields($table))) { extend_schema($table, $new_fields, $data); } // save $columns = implode("`, `", array_keys($data)); $qm = str_repeat(",?", count(array_keys($data)) - 1); echo ("INSERT INTO `$table` (`$columns`) VALUES (?$qm);"); function known_fields($table) { return unserialize(@file_get_contents("db:$table")) ?: array("id"); function extend_schema($table, $new_fields, $data) { foreach ($new_fields as $field) { echo("ALTER TABLE `$table` ADD COLUMN `$field` VARCHAR;"); Since it is mostly meta information fields, adding them just as VARCHAR seems sufficient. Nobody will query by them anyway. So the database is really just used as storage here. However, while I might want to add a lot of new $data fields on the go, they will not always be populated. (2) serialize() fields into BLOB. Any new/extraneous meta fields could be opaque to the database. Simply sorting out the virtual fields from the real database columns is simple. And the meta fields can just be serialize()d into a blob/text field then: function ext_save($data, $table="forum") { $db_fields = array("id", "content", "flags", "ext"); // disjoin foreach (array_diff(array_keys($data),$db_fields) as $key) { $data["ext"][$key] = $data[$key]; unset($data[$key]); } $data["ext"] = serialize($data["ext"]); Unserializing and unpacking this 'ext' column on read queries is a minor overhead. The advantage is that there won't be any sparsely filled columns in the database, so I guess it's compacter and faster than the AUTO ALTER TABLE approach. Of course, this method prevents ever using one of the new fields in a WHERE or GROUP BY clause. But I think none of the possible meta fields (user_agent, author_ip, author_img, votes, hits, last_modified, ..) would/should ever be used there anyway. So I currently prefer the 'ext' blob approach, even if it's a one-way ticket. How are such columns called usually? (looking for examples/doc) Would you use XML serialization for (very theoretical) in-database queries? The adapting table scheme seems a "cleaner" interface, even if most columns might remain empty then. How does that impact speed? How many such sparse VARCHAR fields can MySQL/innodb stomach? But most importantly: Is there any standard implementation for this? A pseudo ORM with automatic ALTER TABLE tricks? Storing a simple column list seems workable, but something like pdo::getColumnMeta would be more robust.

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• I'm looking for a reliable way to verify T-SQL stored procedures. Anybody got one?

  - by Cory Larson

  Hi all-- We're upgrading from SQL Server 2005 to 2008. Almost every database in the 2005 instance is set to 2000 compatibility mode, but we're jumping to 2008. Our testing is complete, but what we've learned is that we need to get faster at it. I've discovered some stored procedures that either SELECT data from missing tables or try to ORDER BY columns that don't exist. Wrapping the SQL to create the procedures in SET PARSEONLY ON and trapping errors in a try/catch only catches the invalid columns in the ORDER BYs. It does not find the error with the procedure selecting data from the missing table. SSMS 2008's intellisense, however, DOES find the issue, but I can still go ahead and successfully run the ALTER script for the procedure without it complaining. So, why can I even get away with creating a procedure that fails when it runs? Are there any tools out there that can do better than what I've tried? The first tool I found wasn't very useful: DbValidator from CodeProject, but it finds fewer problems than this script I found on SqlServerCentral, which found the invalid column references. ------------------------------------------------------------------------- -- Check Syntax of Database Objects -- Copyrighted work. Free to use as a tool to check your own code or in -- any software not sold. All other uses require written permission. ------------------------------------------------------------------------- -- Turn on ParseOnly so that we don't actually execute anything. SET PARSEONLY ON GO -- Create a table to iterate through declare @ObjectList table (ID_NUM int NOT NULL IDENTITY (1, 1), OBJ_NAME varchar(255), OBJ_TYPE char(2)) -- Get a list of most of the scriptable objects in the DB. insert into @ObjectList (OBJ_NAME, OBJ_TYPE) SELECT name, type FROM sysobjects WHERE type in ('P', 'FN', 'IF', 'TF', 'TR', 'V') order by type, name -- Var to hold the SQL that we will be syntax checking declare @SQLToCheckSyntaxFor varchar(max) -- Var to hold the name of the object we are currently checking declare @ObjectName varchar(255) -- Var to hold the type of the object we are currently checking declare @ObjectType char(2) -- Var to indicate our current location in iterating through the list of objects declare @IDNum int -- Var to indicate the max number of objects we need to iterate through declare @MaxIDNum int -- Set the inital value and max value select @IDNum = Min(ID_NUM), @MaxIDNum = Max(ID_NUM) from @ObjectList -- Begin iteration while @IDNum <= @MaxIDNum begin -- Load per iteration values here select @ObjectName = OBJ_NAME, @ObjectType = OBJ_TYPE from @ObjectList where ID_NUM = @IDNum -- Get the text of the db Object (ie create script for the sproc) SELECT @SQLToCheckSyntaxFor = OBJECT_DEFINITION(OBJECT_ID(@ObjectName, @ObjectType)) begin try -- Run the create script (remember that PARSEONLY has been turned on) EXECUTE(@SQLToCheckSyntaxFor) end try begin catch -- See if the object name is the same in the script and the catalog (kind of a special error) if (ERROR_PROCEDURE() <> @ObjectName) begin print 'Error in ' + @ObjectName print ' The Name in the script is ' + ERROR_PROCEDURE()+ '. (They don''t match)' end -- If the error is just that this already exists then we don't want to report that. else if (ERROR_MESSAGE() <> 'There is already an object named ''' + ERROR_PROCEDURE() + ''' in the database.') begin -- Report the error that we got. print 'Error in ' + ERROR_PROCEDURE() print ' ERROR TEXT: ' + ERROR_MESSAGE() end end catch -- Setup to iterate to the next item in the table select @IDNum = case when Min(ID_NUM) is NULL then @IDNum + 1 else Min(ID_NUM) end from @ObjectList where ID_NUM > @IDNum end -- Turn the ParseOnly back off. SET PARSEONLY OFF GO Any suggestions?

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• convert pixels into image

  - by Zeta Op

  what i am trying to do is to convert a pixel from a video cam, into an image to expalin it better imagine a 3d model so.. the pixels would be each polying, and i want to do is to conver each polyigon into an image. what i have so far is this ** import processing.video.*; PImage hoja; Capture cam; boolean uno, dos, tres, cuatro; import ddf.minim.*; Minim minim; AudioPlayer audio; float set; void setup() { //audio minim = new Minim(this); // audio = minim.loadFile("audio"); // audio.loop(); // uno=false; dos=false; tres=false; cuatro=true; size(640, 480); hoja=loadImage("hoja.gif"); cam = new Capture(this, width, height); cam.start(); } void draw() { if (cam.available() == true) { cam.read(); if (uno==true) { filtroUno(); image(cam, 0, 0, 640, 480); } if (dos==true) { filtroDos(); } if(tres==true){ filtroTres(); } if(cuatro==true){ filtroCuatro(); image(cam, set, 0,640,480); } } // The following does the same, and is faster when just drawing the image // without any additional resizing, transformations, or tint. //set(0, 0, cam); } void filtroUno() { cam.loadPixels(); hoja.loadPixels(); for (int i=0;i<cam.pixels.length;i++) { if (brightness(cam.pixels[i])>110) { cam.pixels[i]=color(0, 255, 255); } else { cam.pixels[i]=color(255, 0, 0); } } for (int i=0;i<cam.width;i+=10) { for (int j=0;j<cam.height;j+=10) { int loc=i+(j*cam.width); if (cam.pixels[loc]==color(255, 0, 0)) { for (int x=i;x<i+10;x++) { for (int y=j;y<j+10;y++) { // println("bla"); int locDos=i+(j*cam.width); cam.pixels[locDos]=hoja.get(x, y); } } } } } cam.updatePixels(); } ** the broblem is that each pixel is creating me a matrix, so.. is not recreating what id that to do. i had the method filtroUno but it wasn't showing ok.. and was the result void filtroUno() { cam.loadPixels(); hoja.loadPixels(); for (int i=0;i<cam.pixels.length;i++) { if (brightness(cam.pixels[i])>110) { cam.pixels[i]=color(0, 255, 255); } else { cam.pixels[i]=color(255, 0, 0); } } for (int i=0;i<cam.width;i+=10) { for (int j=0;j<cam.height;j+=10) { int loc=i+j*hoja.width*10; if (cam.pixels[loc]==color(255, 0, 0)) { for (int x=i;x<i+10;x++) { for (int y=j;y<j+10;y++) { // println("bla"); int locDos=x+y*hoja.height*10; cam.pixels[locDos]=hoja.get(x, y); } } } } } cam.updatePixels(); } i hope you can help me thanks note: each red pixel should be the gif image the imge size is 10x10

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• Do you know of a C macro to compute Unix time and date?

  - by Alexis Wilke

  I'm wondering if someone knows/has a C macro to compute a static Unix time from a hard coded date and time as in: time_t t = UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13); I'm looking into that because I want to have a numeric static timestamp. This will be done hundred of times throughout the software, each time with a different date, and I want to make sure it is fast because it will run hundreds of times every second. Converting dates that many times would definitively slow down things (i.e. calling mktime() is slower than having a static number compiled in place, right?) [made an update to try to render this paragraph clearer, Nov 23, 2012] Update I want to clarify the question with more information about the process being used. As my server receives requests, for each request, it starts a new process. That process is constantly updated with new plugins and quite often such updates require a database update. Those must be run only once. To know whether an update is necessary, I want to use a Unix date (which is better than using a counter because a counter is much more likely to break once in a while.) The plugins will thus receive an update signal and have their on_update() function called. There I want to do something like this: void some_plugin::on_update(time_t last_update) { if(last_update < UNIX_TIMESTAMP(2010, 3, 22, 20, 9, 26)) { ...run update... } if(last_update < UNIX_TIMESTAMP(2012, 5, 10, 9, 26, 13)) { ...run update... } // as many test as required... } As you can see, if I have to compute the unix timestamp each time, this could represent thousands of calls per process and if you receive 100 hits a second x 1000 calls, you wasted 100,000 calls when you could have had the compiler compute those numbers once at compile time. Putting the value in a static variable is of no interest because this code will run once per process run. Note that the last_update variable changes depending on the website being hit (it comes from the database.) Code Okay, I got the code now: // helper (Days in February) #define _SNAP_UNIX_TIMESTAMP_FDAY(year) \ (((year) % 400) == 0 ? 29LL : \ (((year) % 100) == 0 ? 28LL : \ (((year) % 4) == 0 ? 29LL : \ 28LL))) // helper (Days in the year) #define _SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) \ ( \ /* January */ static_cast<qint64>(day) \ /* February */ + ((month) >= 2 ? 31LL : 0LL) \ /* March */ + ((month) >= 3 ? _SNAP_UNIX_TIMESTAMP_FDAY(year) : 0LL) \ /* April */ + ((month) >= 4 ? 31LL : 0LL) \ /* May */ + ((month) >= 5 ? 30LL : 0LL) \ /* June */ + ((month) >= 6 ? 31LL : 0LL) \ /* July */ + ((month) >= 7 ? 30LL : 0LL) \ /* August */ + ((month) >= 8 ? 31LL : 0LL) \ /* September */+ ((month) >= 9 ? 31LL : 0LL) \ /* October */ + ((month) >= 10 ? 30LL : 0LL) \ /* November */ + ((month) >= 11 ? 31LL : 0LL) \ /* December */ + ((month) >= 12 ? 30LL : 0LL) \ ) #define SNAP_UNIX_TIMESTAMP(year, month, day, hour, minute, second) \ ( /* time */ static_cast<qint64>(second) \ + static_cast<qint64>(minute) * 60LL \ + static_cast<qint64>(hour) * 3600LL \ + /* year day (month + day) */ (_SNAP_UNIX_TIMESTAMP_YDAY(year, month, day) - 1) * 86400LL \ + /* year */ (static_cast<qint64>(year) - 1970LL) * 31536000LL \ + ((static_cast<qint64>(year) - 1969LL) / 4LL) * 86400LL \ - ((static_cast<qint64>(year) - 1901LL) / 100LL) * 86400LL \ + ((static_cast<qint64>(year) - 1601LL) / 400LL) * 86400LL ) WARNING: Do not use these macros to dynamically compute a date. It is SLOWER than mktime(). This being said, if you have a hard coded date, then the compiler will compute the time_t value at compile time. Slower to compile, but faster to execute over and over again.

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• Fastest way to pad a number in Java to a certain number of digits

  - by Martin

  Am trying to create a well-optimised bit of code to create number of X-digits in length (where X is read from a runtime properties file), based on a DB-generated sequence number (Y), which is then used a folder-name when saving a file. I've come up with three ideas so far, the fastest of which is the last one, but I'd appreciate any advice people may have on this... 1) Instantiate a StringBuilder with initial capacity X. Append Y. While length < X, insert a zero at pos zero. 2) Instantiate a StringBuilder with initial capacity X. While length < X, append a zero. Create a DecimalFormat based on StringBuilder value, and then format the number when it's needed. 3) Create a new int of Math.pow( 10, X ) and add Y. Use String.valueOf() on the new number and then substring(1) it. The second one can obviously be split into outside-loop and inside-loop sections. So, any tips? Using a for-loop of 10,000 iterations, I'm getting similar timings from the first two, and the third method is approximately ten-times faster. Does this seem correct? Full test-method code below... // Setup test variables int numDigits = 9; int testNumber = 724; int numIterations = 10000; String folderHolder = null; DecimalFormat outputFormat = new DecimalFormat( "#,##0" ); // StringBuilder test long before = System.nanoTime(); for ( int i = 0; i < numIterations; i++ ) { StringBuilder sb = new StringBuilder( numDigits ); sb.append( testNumber ); while ( sb.length() < numDigits ) { sb.insert( 0, 0 ); } folderHolder = sb.toString(); } long after = System.nanoTime(); System.out.println( "01: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" ); // DecimalFormat test before = System.nanoTime(); StringBuilder sb = new StringBuilder( numDigits ); while ( sb.length() < numDigits ) { sb.append( 0 ); } DecimalFormat formatter = new DecimalFormat( sb.toString() ); for ( int i = 0; i < numIterations; i++ ) { folderHolder = formatter.format( testNumber ); } after = System.nanoTime(); System.out.println( "02: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" ); // Substring test before = System.nanoTime(); int baseNum = (int)Math.pow( 10, numDigits ); for ( int i = 0; i < numIterations; i++ ) { int newNum = baseNum + testNumber; folderHolder = String.valueOf( newNum ).substring( 1 ); } after = System.nanoTime(); System.out.println( "03: " + outputFormat.format( after - before ) + " nanoseconds" ); System.out.println( "Sanity check: Folder = \"" + folderHolder + "\"" );

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• Create File Speedily From Individual Column

  - by neversaint

  I have a data that looks like this: -1 1:-0.394668 2:-0.794872 3:-1 4:-0.871341 5:0.9365 6:0.75597 1 1:-0.463641 2:-0.897436 3:-1 4:-0.871341 5:0.44378 6:0.121824 1 1:-0.469432 2:-0.897436 3:-1 4:-0.871341 5:0.32668 6:0.302529 -1 1:-0.241547 2:-0.538462 3:-1 4:-0.871341 5:0.9994 6:0.987166 1 1:-0.757233 2:-0.948718 3:-1 4:-0.871341 5:-0.33904 6:0.915401 1 1:-0.167147 2:-0.589744 3:-1 4:-0.871341 5:0.95078 6:0.991566 The first column is class, and next 6 columns are features. I want to create 6 files for individual features. For example feat1_file.txt will contain -1 1:-0.394668 1 1:-0.463641 ... 1 1:-0.757233 1 1:-0.167147 feat2_file.txt will contain -1 2:-0.794872 ... 1 2:-0.589744 and so on. I have a Perl code that does this but it is horribly slow. Is there a way to do it faster? Typically the input files will contain 100K lines. use strict; use Data::Dumper; use Carp; my $input = $ARGV[0] || "myinput.txt"; my $INFILE_file_name = $input; # input file name open ( INFILE, '<', $INFILE_file_name ) or croak "$0 : failed to open input file $INFILE_file_name : $!\n"; my $out1 = $input."_feat_1.txt"; my $out2 = $input."_feat_2.txt"; my $out3 = $input."_feat_3.txt"; my $out4 = $input."_feat_4.txt"; my $out5 = $input."_feat_5.txt"; my $out6 = $input."_feat_6.txt"; unlink($out1); unlink($out2); unlink($out3); unlink($out4); unlink($out5); unlink($out6); print "$out1\n"; while ( <INFILE> ) { chomp; my @els = split(/\s+/,$_); my $lbl = $els[0]; my $OUTFILE1_file_name = $out1; # output file name open ( OUTFILE1, '>>', $OUTFILE1_file_name ) or croak "$0 : failed to open output file $OUTFILE1_file_name : $!\n"; print OUTFILE1 "$lbl $els[1]\n"; close ( OUTFILE1 ); # close output file my $OUTFILE2_file_name = $out2; # output file name open ( OUTFILE2, '>>', $OUTFILE2_file_name ) or croak "$0 : failed to open output file $OUTFILE2_file_name : $!\n"; print OUTFILE2 "$lbl $els[2]\n"; close ( OUTFILE2 ); # close output file # Etc.. until OUTFILE 6 } close (INFILE);

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• CSS optimization - extra classes in dom or preprocessor-repetitive styling in css file?

  - by anna.mi

  I'm starting on a fairly large project and I'm considering the option of using LESS for pre-processing my css. the useful thing about LESS is that you can define a mixin that contains for example: .border-radius(@radius) { -webkit-border-radius: @radius; -moz-border-radius: @radius; -o-border-radius: @radius; -ms-border-radius: @radius; border-radius: @radius; } and then use it in a class declaration as .rounded-div { .border-radius(10px); } to get the outputted css as: .rounded-div { -webkit-border-radius: 10px; -moz-border-radius: 10px; -o-border-radius: 10px; -ms-border-radius: 10px; border-radius: 10px; } this is extremely useful in the case of browser prefixes. However this same concept could be used to encapsulate commonly-used css, for example: .column-container { overflow: hidden; display: block; width: 100%; } .column(@width) { float: left; width: @width; } and then use this mixin whenever i need columns in my design: .my-column-outer { .column-container(); background: red; } .my-column-inner { .column(50%); font-color: yellow; } (of course, using the preprocessor we could easily expand this to be much more useful, eg. pass the number of columns and the container width as variables and have LESS determine the width of each column depending on the number of columns and container width!) the problem with this is that when compliled, my final css file would have 100 such declarations, copy&pasted, making the file huge and bloated and repetitive. The alternative to this would be to use a grid system which has predefined classes for each column-layout option, eg .c-50 ( with a "float: left; width:50%;" definition ), .c-33, .c-25 to accomodate for a 2-column, 3-column and 4-column layout and then use these classes to my dom. i really mislike the idea of the extra classes, from experience it results to bloated dom (creating extra divs just to attach the grid classes to). Also the most basic tutorial for html/css would tell you that the dom should be separated from the styling - grid classes are styling related! to me, its the same as attaching a "border-radius-10" class to the .rounded-div example above! on the other hand, the large css file that would result from the repetitive code is also a disadvantage so i guess my question is, which one would you recommend? and which do you use? and, which solution is best for optimization? apart from the larger file size, has there even been any research on whether browser renders multiple classes faster than a large css file, or the other way round? tnx! i'd love to hear your opinion!

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• Data Warehouse ETL slow - change primary key in dimension?

  - by Jubbles

  I have a working MySQL data warehouse that is organized as a star schema and I am using Talend Open Studio for Data Integration 5.1 to create the ETL process. I would like this process to run once per day. I have estimated that one of the dimension tables (dimUser) will have approximately 2 million records and 23 columns. I created a small test ETL process in Talend that worked, but given the amount of data that may need to be updated daily, the current performance will not cut it. It takes the ETL process four minutes to UPDATE or INSERT 100 records to dimUser. If I assumed a linear relationship between the count of records and the amount of time to UPDATE or INSERT, then there is no way the ETL can finish in 3-4 hours (my hope), let alone one day. Since I'm unfamiliar with Java, I wrote the ETL as a Python script and ran into the same problem. Although, I did discover that if I did only INSERT, the process went much faster. I am pretty sure that the bottleneck is caused by the UPDATE statements. The primary key in dimUser is an auto-increment integer. My friend suggested that I scrap this primary key and replace it with a multi-field primary key (in my case, 2-3 fields). Before I rip the test data out of my warehouse and change the schema, can anyone provide suggestions or guidelines related to the design of the data warehouse the ETL process how realistic it is to have an ETL process INSERT or UPDATE a few million records each day will my friend's suggestion significantly help If you need any further information, just let me know and I'll post it. UPDATE - additional information: mysql> describe dimUser; Field Type Null Key Default Extra user_key int(10) unsigned NO PRI NULL auto_increment id_A int(10) unsigned NO NULL id_B int(10) unsigned NO NULL field_4 tinyint(4) unsigned NO 0 field_5 varchar(50) YES NULL city varchar(50) YES NULL state varchar(2) YES NULL country varchar(50) YES NULL zip_code varchar(10) NO 99999 field_10 tinyint(1) NO 0 field_11 tinyint(1) NO 0 field_12 tinyint(1) NO 0 field_13 tinyint(1) NO 1 field_14 tinyint(1) NO 0 field_15 tinyint(1) NO 0 field_16 tinyint(1) NO 0 field_17 tinyint(1) NO 1 field_18 tinyint(1) NO 0 field_19 tinyint(1) NO 0 field_20 tinyint(1) NO 0 create_date datetime NO 2012-01-01 00:00:00 last_update datetime NO 2012-01-01 00:00:00 run_id int(10) unsigned NO 999 I used a surrogate key because I had read that it was good practice. Since, from a business perspective, I want to keep aware of potential fraudulent activity (say for 200 days a user is associated with state X and then the next day they are associated with state Y - they could have moved or their account could have been compromised), so that is why geographic data is kept. The field id_B may have a few distinct values of id_A associated with it, but I am interested in knowing distinct (id_A, id_B) tuples. In the context of this information, my friend suggested that something like (id_A, id_B, zip_code) be the primary key. For the large majority of daily ETL processes (80%), I only expect the following fields to be updated for existing records: field_10 - field_14, last_update, and run_id (this field is a foreign key to my etlLog table and is used for ETL auditing purposes).

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• SQL: Using a CASE Statement to update a 1000 rows at once, how??

  - by SoLoGHoST

  Ok, I would like to use a CASE STATEMENT for this, but I am lost with this. Basically, I need to update a ton of rows, but just on the "position" column. I need to update all "position" values from 0 - count(position) for each id_layout_position column per id_layout column. Here's what I got for a regular update, but I don't wanna throw this into a foreach loop, as it would take forever to do it. I'm using SMF (Simple Machines Forums), so it might look a little different, but the idea is the same, and CASE statements are supported... $smcFunc['db_query']('', ' UPDATE {db_prefix}dp_positions SET position = {int:position} WHERE id_layout_position = {int:id_layout_position} AND id_layout = {int:id_layout}', array( 'position' => $position++, 'id_layout_position' => (int) $id_layout_position, 'id_layout' => (int) $id_layout, ) ); Anyways, I need to apply some sort of CASE on this so that I can auto-increment by 1 all values that it finds and update to the next possible value. I know I'm doing this wrong, even in this QUERY. But I'm totally lost when it comes to CASES. Here's an example of a CASE being used within SMF, so you can see this and hopefully relate: $conditions = ''; foreach ($postgroups as $id => $min_posts) { $conditions .= ' WHEN posts >= ' . $min_posts . (!empty($lastMin) ? ' AND posts <= ' . $lastMin : '') . ' THEN ' . $id; $lastMin = $min_posts; } // A big fat CASE WHEN... END is faster than a zillion UPDATE's ;). $smcFunc['db_query']('', ' UPDATE {db_prefix}members SET id_post_group = CASE ' . $conditions . ' ELSE 0 END' . ($parameter1 != null ? ' WHERE ' . (is_array($parameter1) ? 'id_member IN ({array_int:members})' : 'id_member = {int:members}') : ''), array( 'members' => $parameter1, ) ); Before I do the update, I actually have a SELECT which throws everything I need into arrays like so: $disabled_sections = array(); $positions = array(); while ($row = $smcFunc['db_fetch_assoc']($request)) { if (!isset($disabled_sections[$row['id_group']][$row['id_layout']])) $disabled_sections[$row['id_group']][$row['id_layout']] = array( 'info' => $module_info[$name], 'id_layout_position' => $row['id_layout_position'] ); // Increment the positions... if (!is_null($row['position'])) { if (!isset($positions[$row['id_layout']][$row['id_layout_position']])) $positions[$row['id_layout']][$row['id_layout_position']] = 1; else $positions[$row['id_layout']][$row['id_layout_position']]++; } else $positions[$row['id_layout']][$row['id_layout_position']] = 0; } Thanks, I know if anyone can help me here it's definitely you guys and gals... Anyways, here is my question: How do I use a CASE statement in the first code example, so that I can update all of the rows in the position column from 0 - total # of rows found, that have that id_layout value and that id_layout_position value, and continue this for all different id_layout values in that table? Can I use the arrays above somehow? I'm sure I'll have to use the id_layout and id_layout_position values for this right? But how can I do this?

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• Optimizing JS Array Search

  - by The.Anti.9

  I am working on a Browser-based media player which is written almost entirely in HTML 5 and JavaScript. The backend is written in PHP but it has one function which is to fill the playlist on the initial load. And the rest is all JS. There is a search bar that refines the playlist. I want it to refine as the person is typing, like most media players do. The only problem with this is that it is very slow and laggy as there are about 1000 songs in the whole program and there is likely to be more as time goes on. The original playlist load is an ajax call to a PHP page that returns the results as JSON. Each item has 4 attirbutes: artist album file url I then loop through each object and add it to an array called playlist. At the end of the looping a copy of playlist is created, backup. This is so that I can refine the playlist variable when people refine their search, but still repopulated it from backup without making another server request. The method refine() is called when the user types a key into the searchbox. It flushes playlist and searches through each property (not including url) of each object in the backup array for a match in the string. If there is a match in any of the properties, it appends the information to a table that displays the playlist, and adds it to the object to playlist for access by the actual player. Code for the refine() method: function refine() { $('#loadinggif').show(); $('#library').html("<table id='libtable'><tr><th>Artist</th><th>Album</th><th>File</th><th>&nbsp;</th></tr></table>"); playlist = []; for (var j = 0; j < backup.length; j++) { var sfile = new String(backup[j].file); var salbum = new String(backup[j].album); var sartist = new String(backup[j].artist); if (sfile.toLowerCase().search($('#search').val().toLowerCase()) !== -1 || salbum.toLowerCase().search($('#search').val().toLowerCase()) !== -1 || sartist.toLowerCase().search($('#search').val().toLowerCase()) !== -1) { playlist.push(backup[j]); num = playlist.length-1; $("<tr></tr>").html("<td>" + num + "</td><td>" + sartist + "</td><td>" + salbum + "</td><td>" + sfile + "</td><td><a href='#' onclick='setplay(" + num +");'>Play</a></td>").appendTo('#libtable'); } } $('#loadinggif').hide(); } As I said before, for the first couple of letters typed, this is very slow and laggy. I am looking for ways to refine this to make it much faster and more smooth.

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• Bootstrap toggleable tag

  - by user1869816

  I am a newbies to bootstrap. I have tried to play with the code to make a page with toggleable tag. However, I have checked my code for many times but I still can't find the problem in my code. Would anyone help me, please? <div class="row"> <div class="tabbable"> <ul class="nav nav-tabs" id="tabs" data-tabs="tabs"> <li class="active"><a href="#having_a" data-toggle="tab">Having a</a></li> <li><a href="#having_b" data-toggle="tab">Having b</a></li> <li><a href="#having_c" data-toggle="tab">Having c</a></li> </ul> <!-- content of the tab --> <div class="tab-content" id="tab-content"> <div class="tab-pane active" id="having_a"> <p>a</p> </div> <div class="tab-pane" id="having_b"> <p>b</p> </div> <div class="tab-pane" id="having_c"> <p>c</p> </div> </div> </div> <script type="text/javascript"> jQuery(document).ready(function ($) {$('#tabs').tab(); }); </script> </div> <hr> <footer> <p>&copy;2012</p> </footer> </div> <!-- /container --> <!-- Le javascript ================================================== --> <!-- Placed at the end of the document so the pages load faster --> <script src="js/jquery.js"></script> <script src="js/bootstrap-transition.js"></script> <script src="js/bootstrap-alert.js"></script> <script src="js/bootstrap-modal.js"></script> <script src="js/bootstrap-dropdown.js"></script> <script src="js/bootstrap-scrollspy.js"></script> <script src="js/bootstrap-tab.js"></script> <script src="js/bootstrap-tooltip.js"></script> <script src="js/bootstrap-popover.js"></script> <script src="js/bootstrap-button.js"></script> <script src="js/bootstrap-collapse.js"></script> <script src="js/bootstrap-carousel.js"></script>

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