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  • writing to a dataframe from a for-loop in R

    - by CCID
    I'm trying to write from a loop to a data frame in R, for example a loop like this for (i in 1:20) { print(c(i+i,i*i,i/1))} and to write each line of 3 values to a data frame with three columns, so that each iteration takes on a new row. I've tried using matrix, with ncol=3 and filled by rows, but only get the last item from the loop. Thanks.

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  • For loop with a non-integer increment in VB.NET

    - by Dan Tao
    Can a VB.NET For loop be constructed that mimics this C# code? TimeSpan oneDay = TimeSpan.FromDays(1.0); for (DateTime d = startDate; d < endDate; d += oneDay) { // some code } Obviously you could do it without a For loop (i.e., with a While); I'm just curious if there's a certain syntax to construct a VB.NET For loop with a non-integer increment that I'm not aware of.

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  • PHP While loop seperating unique categories from multiple 'Joined' tables

    - by Hob
    I'm pretty new to Joins so hope this all makes sense. I'm joining 4 tables and want to create a while loop that spits out results nested under different categories. My Tables categories id | category_name pages id | page_name | category *page_content* id | page_id | image_id images id | thumb_path My current SQL join <?php $all_photos = mysql_query(" SELECT * FROM categories JOIN pages ON pages.category = categories.id JOIN image_pages ON image_pages.page_id = pages.id JOIN images ON images.id = image_pages.image_id ");?> The result I want from a while loop I would like to get something like this.... Category 1 page 1 Image 1, image 2, image 3 page 2 Image 2, image 4 Category 2 page 3 image 1 page 4 image 1, image 2, image 3 I hope that makes sense. Each image can fall under multiple pages and each page can fall under multiple categories. at the moment I have 2 solutions, one which lists each category several times according to the the amount of pages inside them: eg. category 1, page 1, image 1 - category 1, page 1, image 2 etc One that uses a while loop inside another while loop inside another while loop, resulting in 3 sql queries. <?php while($all_page = mysql_fetch_array($all_pages)) { ?> <p><?=$all_page['page_name']?></p> <?php $all_images = mysql_query("SELECT * FROM images JOIN image_pages ON image_pages.page_id = " . $all_page['id'] . " AND image_pages.image_id = images.id"); ?> <div class="admin-images-block clearfix"> <?php while($all_image = mysql_fetch_array($all_images)) { ?> <img src="<?=$all_image['thumb_path']?>" alt="<?=$all_image['title']?>"/> <?php } ?> </div> <?php } } ?

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  • Java - 'continue' loop iteration after certain timeout period

    - by Matt
    Is there a way to exit ('continue;') a loop iteration after a certain timeout period? I have a loop that will run gathering data from the web and then use this data to make a calculation. The data become obsolete after about 1 to 2 seconds so if the loop iteration takes longer than 1 second then i want it to 'continue' to the next iteration. Sometimes gathering the data can take time but sometimes the calculation can take longer than 1 second so a HTTP timeout won't work for what i need. Also, while doing the calculation the thread i am using is blocked so i cannot check System.currentTimeMillis(); Is there a way to use another Thread to check the time and force the original for loop to continue.

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  • Why does this game loop stop my process from responding?

    - by Ben
    I implemented a fixed time step loop for my C# game. All it does at the moment is make a square bounce around the screen. The problem I'm having is that when I execute the program, I can't close it from the window's close button and the cursor is stuck on the "busy" icon. I have to go into Visual Studio and stop the program manually. Here's the loop at the moment: public void run() { int updates = 0; int frames = 0; double msPerTick = 1000.0 / 60.0; double threshhold = 0; long lastTime = getCurrentTime(); long lastTimer = getCurrentTime(); while (true) { long currTime = getCurrentTime(); threshhold += (currTime - lastTime) / msPerTick; lastTime = currTime; while (threshhold >= 1) { update(); updates++; threshhold -= 1; } this.Refresh(); frames++; if ((getCurrentTime() - lastTimer) >= 1000) { this.Text = updates + " updates and " + frames + " frames per second"; updates = 0; frames = 0; lastTimer += 1000; } } } Why is this happening?

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  • [UNIX] Sort lines of massive file by number of words on line (ideally in parallel)

    - by conradlee
    I am working on a community detection algorithm for analyzing social network data from Facebook. The first task, detecting all cliques in the graph, can be done efficiently in parallel, and leaves me with an output like this: 17118 17136 17392 17064 17093 17376 17118 17136 17356 17318 12345 17118 17136 17356 17283 17007 17059 17116 Each of these lines represents a unique clique (a collection of node ids), and I want to sort these lines in descending order by the number of ids per line. In the case of the example above, here's what the output should look like: 17118 17136 17356 17318 12345 17118 17136 17356 17283 17118 17136 17392 17064 17093 17376 17007 17059 17116 (Ties---i.e., lines with the same number of ids---can be sorted arbitrarily.) What is the most efficient way of sorting these lines. Keep the following points in mind: The file I want to sort could be larger than the physical memory of the machine Most of the machines that I'm running this on have several processors, so a parallel solution would be ideal An ideal solution would just be a shell script (probably using sort), but I'm open to simple solutions in python or perl (or any language, as long as it makes the task simple) This task is in some sense very easy---I'm not just looking for any old solution, but rather for a simple and above all efficient solution

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  • Perl Parallel::ForkManager wait_all_children() takes excessively long time

    - by zhang18
    I have a script that uses Parallel::ForkManager. However, the wait_all_children() process takes incredibly long time even after all child-processes are completed. The way I know is by printing out some timestamps (see below). Does anyone have any idea what might be causing this (I have 16 CPU cores on my machine)? my $pm = Parallel::ForkManager->new(16) for my $i (1..16) { $pm->start($i) and next; ... do something within the child-process ... print (scalar localtime), " Process $i completed.\n"; $pm->finish(); } print (scalar localtime), " Waiting for some child process to finish.\n"; $pm->wait_all_children(); print (scalar localtime), " All processes finished.\n"; Clearly, I'll get the Waiting for some child process to finish message first, with a timestamp of, say, 7:08:35. Then I'll get a list of Process i completed messages, with the last one at 7:10:30. However, I do not receive the message All Processes finished until 7:16:33(!). Why is that 6-minute delay between 7:10:30 and 7:16:33? Thx!

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  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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  • Parallel.For Batching

    - by chibacity
    Is there built-in support in the TPL for batching operations? I was recently playing with a routine to carry out character replacement on a character array which required a lookup table i.e. transliteration: for (int i = 0; i < chars.Length; i++) { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } } I could see that this could be trivially parallelized, so jumped in with a first stab which I knew would perform worse as the tasks were too fine-grained: Parallel.For(0, chars.Length, i => { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } }); I then reworked the algorithm to use batching so that the work could be chunked onto different threads in less fine-grained batches. This made use of threads as expected and I got some near linear speed up. I'm sure that there must be built-in support for batching in the TPL. What is the syntax, and how do I use it? const int CharBatch = 100; int charLen = chars.Length; Parallel.For(0, ((charLen / CharBatch) + 1), i => { int batchUpper = ((i + 1) * CharBatch); for (int j = i * CharBatch; j < batchUpper && j < charLen; j++) { char replaceChar; if (lookup.TryGetValue(chars[j], out replaceChar)) { chars[j] = replaceChar; } } });

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  • Build OpenGL model in parallel?

    - by Brendan Long
    I have a program which draws some terrain and simulates water flowing over it (in a cheap and easy way). Updating the water was easy to parallelize using OpenMP, so I can do ~50 updates per second. The problem is that even with a small amounts of water, my draws per second are very very low (starts at 5 and drops to around 2 once there's a significant amount of water). It's not a problem with the video card because the terrain is more complicated and gets drawn so quickly that boost::timer tells me that I get infinity draws per second if I turn the water off. It may be related to memory bandwidth though (since I assume the model stays on the card and doesn't have to be transfered every time). What I'm concerned about is that on every draw, I'm calling glVertex3f() about a million times (max size is 450*600, 4 vertices each), and it's done entirely sequentially because Glut won't let me call anything in parallel. So.. is if there's some way of building the list in parallel and then passing it to OpenGL all at once? Or some other way of making it draw this faster? Am I using the wrong method (besides the obvious "use less vertices")?

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  • Dividing sections inside an omp parallel for : OpenMP

    - by Sayan Ghosh
    Hi, I have a situation like: #pragma omp parallel for private(i, j, k, val, p, l) for (i = 0; i < num1; i++) { for (j = 0; j < num2; j++) { for (k = 0; k < num3; k++) { val = m[i + j*somenum + k*2] if (val != 0) for (l = start; l <= end; l++) { someFunctionThatWritesIntoGlobalArray((i + l), j, k, (someFunctionThatGetsValueFromAnotherArray((i + l), j, k) * val)); } } } for (p = 0; p < num4; p++) { m[p] = 0; } } Thanks for reading, phew! Well I am noticing a very minor difference in the results (0.999967[omp] against 1[serial]), when I use the above (which is 3 times faster) against the serial implementation. Now I know I am doing a mistake here...especially the connection between loops is evident. Is it possible to parallelize this using omp sections? I tried some options like making shared(p) {doing this, I got correct values, as in the serial form}, but there was no speedup then. Any general advice on handling openmp pragmas over a slew of for loops would also be great for me!

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  • Parallel Processing Simulation in Javascript

    - by le_havre
    Hello, I'm new to JavaScript so forgive me for being a n00b. When there's intensive calculation required, it more than likely involves loops that are recursive or otherwise. Sometimes this may mean having am recursive loop that runs four functions and maybe each of those functions walks the entire DOM tree, read positions and do some math for collision detection or whatever. While the first function is walking the DOM tree, the next one will have to wait its for the first one to finish, and so forth. Instead of doing this, why not launch those loops-within-loops separately, outside the programs, and act on their calculations in another loop that runs slower because it isn't doing those calculations itself? Retarded or clever? Thanks in advance!

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  • opening adobe reader results in infinite explorer.exe process creation loop

    - by irrational John
    First, apologies if the answer to this is only a Google away. I tried, honest I did. But I wasn't able to find anything about this problem posted elsewhere. I'm using Adobe Reader v9.3.2 in Windows 7 Home Premium 64-bit. If you want more system details, then just request them. What happens is that when I attempt to open a PDF by clicking "Open" on it then (1) adobe reader never opens and (2) the explorer.exe program is (apparently) recursively opened. I base this on opening the Task Manager and seeing a long list of explorer.exe processes under the "Processes" tab. Usually there is only one. When I recreate this problem, the list of explorer.exe processes are at least a page or two long. (Too many to bother counting). I "correct" this problem by logging off and then logging back on. This kills all the explorer.exe tasks. Unfortunately I don't know another way to terminate them all. Now here's the curious part. This only happens when I attempt to "Open" a PDF file. If instead I use the context menu (right mouse click on the PDF) and select "Open with" and "Adobe Reader 9.3" then Adobe Reader opens the file with no problem. It seems that there is something wrong with the setting for the default open action for PDF files. However, I have been unable to fix this by changing the Windows setting. Here is what I have tried. When I open Control Panel > All Control Panel Items > Default Programs > Set Associations I do not find an entry for file type .pdf. There are only entries for .pdfxml and .pdx. When use "Open with" on a PDF file and select "Choose default program", the check box for "Always use the selected program to open this kind of file" is disabled (greyed out). I have uninstalled and reinstalled Adobe Reader but the problem persists. While obviously no lives are at stake here, this problem is annoying the frickin' heck out of me. If I forget and recreate this bug then I have to stop everything I'm doing to stop it. Any suggestions on how I might go about fixing this?

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  • For Loop counting from 1 to n in a windows bat script

    - by raoulsson
    I need to run a windows command n times within a bat script file. I know how to do this in various programming languages but cannot manage to get it right on the windows command line :-( I would expect something like either for(int i = 0; i < 100; i++) { // do something } or even this (though not entirely seriously) 1.upto(100, { // do something }) Thanks! EDIT I can write a program in java, perl, c or whatever that will generate a bat script that looks like this for %%N in (1 2 3 4 5 6 7 8 9 10 11 12) do echo %%N and so on. Or even "better": echo 1 echo 2 echo 3 echo 4 echo 5 echo 6 echo 7 echo 8 echo 9 echo 10 echo 11 echo 12 and then execute it... But the thing is that I need a concise way to specify a range of numbers to iterate through within the script. Thanks!

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  • Parallel processing in R 2.11 Windows 64-bit using SNOW not quite working

    - by Abhijit
    I'm running R 2.11 64-bit on a WinXP64 machine with 8 processors. With R 2.10.1 the following code spawned 6 R processes for parallel processing: require(foreach) require(doSNOW) cl = makeCluster(6, type='SOCK') registerDoSNOW(cl) bl2 = foreach(i=icount(length(unqmrno))) %dopar% { (Some code here) } stopCluster(cl) When I run the same code in R 2.11 Win64, the 6 R processes are not spawning, and the code hangs. I'm wondering if this is a problem with the port of SNOW to 2.11-64bit, or if any additional code is required on my part. Thanks

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  • Parallel computing for integrals

    - by Iman
    I want to reduce the calculation time for a time-consuming integral by splitting the integration range. I'm using C++, Windows, and a quad-core Intel i7 CPU. How can I split it into 4 parallel computations?

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  • running a parallel port controlling program through php.

    - by prateek
    I have a program that is interacting with hardware via parallel port programming. i had compiled it and using its object file to interact with the hardware (a simple led). when i execute it directly on the shell it serves the purpose of glowing the LED but when i execute it using shell_exec() in php the command is executed but unable to interact with the hardware. i am totally confused.. .

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  • Parallel programming in C#

    - by Alxandr
    I'm interested in learning about parallel programming in C#.NET (not like everything there is to know, but the basics and maybe some good-practices), therefore I've decided to reprogram an old program of mine which is called ImageSyncer. ImageSyncer is a really simple program, all it does is to scan trough a folder and find all files ending with .jpg, then it calculates the new position of the files based on the date they were taken (parsing of xif-data, or whatever it's called). After a location has been generated the program checks for any existing files at that location, and if one exist it looks at the last write-time of both the file to copy, and the file "in its way". If those are equal the file is skipped. If not a md5 checksum of both files is created and matched. If there is no match the file to be copied is given a new location to be copied to (for instance, if it was to be copied to "C:\test.jpg" it's copied to "C:\test(1).jpg" instead). The result of this operation is populated into a queue of a struct-type that contains two strings, the original file and the position to copy it to. Then that queue is iterated over untill it is empty and the files are copied. In other words there are 4 operations: 1. Scan directory for jpegs 2. Parse files for xif and generate copy-location 3. Check for file existence and if needed generate new path 4. Copy files And so I want to rewrite this program to make it paralell and be able to perform several of the operations at the same time, and I was wondering what the best way to achieve that would be. I've came up with two different models I can think of, but neither one of them might be any good at all. The first one is to parallelize the 4 steps of the old program, so that when step one is to be executed it's done on several threads, and when the entire of step 1 is finished step 2 is began. The other one (which I find more interesting because I have no idea of how to do that) is to create a sort of worker and consumer model, so when a thread is finished with step 1 another one takes over and performs step 2 at that object (or something like that). But as said, I don't know if any of these are any good solutions. Also, I don't know much about parallel programming at all. I know how to make a thread, and how to make it perform a function taking in an object as its only parameter, and I've also used the BackgroundWorker-class on one occasion, but I'm not that familiar with any of them. Any input would be appreciated.

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  • JRuby-friendly method for parallel-testing Rails app

    - by Toby Hede
    I am looking for a system to parallelise a large suite of tests in a Ruby on Rails app (using rspec, cucumber) that works using JRuby. Cucumber is actually not too bad, but the full rSpec suite currently takes nearly 20 minutes to run. The systems I can find (hydra, parallel-test) look like they use forking, which isn't the ideal solution for the JRuby environment.

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