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• Which is the best jQuery-powered site?

  - by Reigel

  This "Top 10 JavaScript (jQuery) Powered Sites", posted about 2 years ago, was the one that invites me(after seeing the list) to use jQuery. All the sites in that list made me realize how cool it is to build sites powered by jQuery. And now more and more sites are being powered by jQuery. More and more developers are learning jQuery. Two years have past now but I still do a search to google for best sites and still got me to that link and which the link is not updated from the first time I have looked at it. Here at stackoverflow, there are lots of jQuery user. I was thinking if we can here show some of the sites that you know that is powered by jQuery which you think is best. If you can, please make it one site one answer, so that we can make a vote if it's really best jQuery powered site. We will take a look if it is really well implemented ( the way the codes are written, fast speed site, etc...) and deserves to be the best. Lot's of viewers will benefit from it. Like, we can view and have an idea of how we will make our next project cooler, faster, and powerful.

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• Where is my python script spending time? Is there "missing time" in my cprofile / pstats trace?

  - by fmark

  I am attempting to profile a long running python script. The script does some spatial analysis on raster GIS data set using the gdal module. The script currently uses three files, the main script which loops over the raster pixels called find_pixel_pairs.py, a simple cache in lrucache.py and some misc classes in utils.py. I have profiled the code on a moderate sized dataset. pstats returns: p.sort_stats('cumulative').print_stats(20) Thu May 6 19:16:50 2010 phes.profile 355483738 function calls in 11644.421 CPU seconds Ordered by: cumulative time List reduced from 86 to 20 due to restriction <20> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.008 0.008 11644.421 11644.421 <string>:1(<module>) 1 11064.926 11064.926 11644.413 11644.413 find_pixel_pairs.py:49(phes) 340135349 544.143 0.000 572.481 0.000 utils.py:173(extent_iterator) 8831020 18.492 0.000 18.492 0.000 {range} 231922 3.414 0.000 8.128 0.000 utils.py:152(get_block_in_bands) 142739 1.303 0.000 4.173 0.000 utils.py:97(search_extent_rect) 745181 1.936 0.000 2.500 0.000 find_pixel_pairs.py:40(is_no_data) 285478 1.801 0.000 2.271 0.000 utils.py:98(intify) 231922 1.198 0.000 2.013 0.000 utils.py:116(block_to_pixel_extent) 695766 1.990 0.000 1.990 0.000 lrucache.py:42(get) 1213166 1.265 0.000 1.265 0.000 {min} 1031737 1.034 0.000 1.034 0.000 {isinstance} 142740 0.563 0.000 0.909 0.000 utils.py:122(find_block_extent) 463844 0.611 0.000 0.611 0.000 utils.py:112(block_to_pixel_coord) 745274 0.565 0.000 0.565 0.000 {method 'append' of 'list' objects} 285478 0.346 0.000 0.346 0.000 {max} 285480 0.346 0.000 0.346 0.000 utils.py:109(pixel_coord_to_block_coord) 324 0.002 0.000 0.188 0.001 utils.py:27(__init__) 324 0.016 0.000 0.186 0.001 gdal.py:848(ReadAsArray) 1 0.000 0.000 0.160 0.160 utils.py:50(__init__) The top two calls contain the main loop - the entire analyis. The remaining calls sum to less than 625 of the 11644 seconds. Where are the remaining 11,000 seconds spent? Is it all within the main loop of find_pixel_pairs.py? If so, can I find out which lines of code are taking most of the time?

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• is mysql index useful on column 'state' when only doing bit-operations on the column?

  - by Geert-Jan

  I have a lot of domain entities (stored in mysql) which undergo lots of different operations. Each operation is executed from a different program. I need to keep (flow)-state for these entities which I implemented in as a long field 'flowstate' used as a bitset. to query mysql for entities which have undergone a certain operation I do something like: select * from entities where state >> 7 & 1 = 1 Indicating bit 7 (cooresponding to operation 7) has run. (<-- simplified) Anyway, I really didn't pay attention to the performance implications of this setup in the beginning, and I think I'm in a bit of trouble since queries as the above run pretty slow. What I'd like to know: Does an mysql index on 'flowstate' help at all? After all it's not a single value Mysql can quickly find using a binary sort or whatever. If it doesn't, are there any other things I could do to speed things up? . Are there special 'mask-indices' for fields with use-cases as the above? TIA, Geert-jan

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• Haskell math performance

  - by Travis Brown

  I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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• Images in database vs file system

  - by Jesse

  We have a project coming up where we will be building a whole backend CMS system that will power our entire extranet and intranet with one package. The question I have been trying to find an answer to is which is better: storing images in the database (SQL Server 2005) so we may have integrity, single replication plan, etc OR storing on the file system? One issue we have is that we have multiple servers load balanced that require to have the same data at all times. As of now we have SQL replication taking care of that but file replication seems to be a little tougher. Another concern we have is that we would like to have multiple resolutions of the same image, we are not sure if creating and storing each version on the file system would be best or maybe dynamically pulling and creating the resolution image we would like upon request. Our concerns are the with the following: Data integrity Data replication Multiple resolutions Speed of database vs file system Overhead load of database vs file system Data management and backup Does anyone have a similar situation or have any input on what would be recommended? Thanks in advance for the help!

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• Self-describing file format for gigapixel images?

  - by Adam Goode

  In medical imaging, there appears to be two ways of storing huge gigapixel images: Use lots of JPEG images (either packed into files or individually) and cook up some bizarre index format to describe what goes where. Tack on some metadata in some other format. Use TIFF's tile and multi-image support to cleanly store the images as a single file, and provide downsampled versions for zooming speed. Then abuse various TIFF tags to store metadata in non-standard ways. Also, store tiles with overlapping boundaries that must be individually translated later. In both cases, the reader must understand the format well enough to understand how to draw things and read the metadata. Is there a better way to store these images? Is TIFF (or BigTIFF) still the right format for this? Does XMP solve the problem of metadata? The main issues are: Storing images in a way that allows for rapid random access (tiling) Storing downsampled images for rapid zooming (pyramid) Handling cases where tiles are overlapping or sparse (scanners often work by moving a camera over a slide in 2D and capturing only where there is something to image) Storing important metadata, including associated images like a slide's label and thumbnail Support for lossy storage What kind of (hopefully non-proprietary) formats do people use to store large aerial photographs or maps? These images have similar properties.

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• How do I stop the m2eclipse plugin interfering with command line mvn builds?

  - by locka

  I use the m2eclipse plugin in Eclipse so that I can import a Maven project. The plugin reads the pom.xml and sorts out the dependencies in the projects in an Eclipse friendly way so I'm not looking at a sea of broken references and errors. I use Eclipse for code development however I usually build the projects from the command line, e.g. "mvn clean install". Unfortunately when I do this, m2eclipse detects disk activity and attempts to rebuild the workspace. This interferes with the command line build and sometimes results in a race condition. For example the command line might be in its clean phase but fails because it tries to delete a file or directory which is locked during the workspace rebuild. Aside from that workspace rebuilding is incredibly slow, and between failed builds and wasted CPU my build process is 2-3x longer than it should be. It isn't an option to not use Eclipse (e.g. to use Netbeans), or to disable m2eclipse. It is a useful plugin except for this behaviour. So my question is, how do I stop m2eclipse from rebuilding the workspace all the time? Can I invoke a manual refresh and otherwise disable this behaviour?

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• PHP / C++ space calculations for parcel packing

  - by Andrew Willis

  I am working on a shopping cart project which requires a 'postage calculator' based on items that the person has in their cart. Obviously I will be storing the item's dimensions incl. weight and padding in a database and will also store the parcel (box) size and weight that the items will go in to, incl. box padding. Figuring the weight of the parcels will be easy but I was wondering how to go about figuring how to pack the box via PHP, that is, I would like the code to 'play tetris' with the items to make sure they get the best possible fit, giving accurate postage costs. Does anybody have any ideas on how best to achieve this or does anybody know of a PHP Class or function that can do this? EDIT: When I said 'best possible fit' maybe I was being optimistic! Having the script try every possible combination of package distribution within the parcel would be over the top, however I could improve the speed by writing the algoritm in C++ and running the program in PHP when the user 'checks out', the return value being an array with the parcel size and weight (which are all that are needed to calculate postage costs)

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• Dependency between operations in scala actors

  - by paradigmatic

  I am trying to parallelise a code using scala actors. That is my first real code with actors, but I have some experience with Java Mulithreading and MPI in C. However I am completely lost. The workflow I want to realise is a circular pipeline and can be described as the following: Each worker actor has a reference to another one, thus forming a circle There is a coordinator actor which can trigger a computation by sending a StartWork() message When a worker receives a StartWork() message, it process some stuff locally and sends DoWork(...) message to its neighbour in the circle. The neighbours do some other stuff and sends in turn a DoWork(...) message to its own neighbour. This continues until the initial worker receives a DoWork() message. The coordinator can send a GetResult() message to the initial worker and wait for a reply. The point is that the coordinator should only receive a result when data is ready. How can a worker wait that the job returned to it before answering the GetResult() message ? To speed up computation, any worker can receive a StartWork() at any time. Here is my first try pseudo-implementation of the worker: class Worker( neighbor: Worker, numWorkers: Int ) { var ready = Foo() def act() { case StartWork() => { val someData = doStuff() neighbor ! DoWork( someData, numWorkers-1 ) } case DoWork( resultData, remaining ) => if( remaining == 0 ) { ready = resultData } else { val someOtherData = doOtherStuff( resultData ) neighbor ! DoWork( someOtherData, remaining-1 ) } case GetResult() => reply( ready ) } } On the coordinator side: worker ! StartWork() val result = worker !? GetResult() // should wait

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• What are some typing patterns using a standard QWERTY keyboard that work well for you as a programme

  - by OrbMan

  After hunting and pecking for about 35 years, I have decided to learn to type. I am learning QWERTY and have learned about 2/3 of the letters so far. While learning, I have noticed how asymmeterical the keyboard is, which really bothers me. (I will probably switch to a symmetrical keyboard eventually, but for now am trying to do everything as standard and "correct" as possible.) Although I am not there yet in my lessons, it seems that many of the keys I am going to use as a C# web developer are supposed to be typed by the pinky of my right hand. Are there any typing patterns you have developed that are more ergonomic (or faster) when typing large volumes of code rife with braces, colons, semi-colons and quotes? Or, should I just accept the fact that every other key is going to be hit with my right pinky? It is not that speed is such a huge concern, as much as that it seems so inefficient to rely on one finger so much... As an example, some of the conventions I use as a hunt and pecker, like typing open and close braces right away with my index and middle finger, and then hitting the left arrow key to fill in the inner content, don't seem to work as well with just a pinky. What are some typing patterns using a standard QWERTY keyboard that work really well for you as a programmer? Update: US layout and I use home row Update 2: Despite my best efforts to the contrary, people are interpreting this questionas "how do I learn to type" or "what keyboard should I use". Take it as a given, that I will learn to type, and that I will be doing so on a standard QWERTY layout keyboard, not DVORAK. I am interested in aquiring a skill that will be useful wherever I go.

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• C# WinForms MultiThreading in Loop

  - by Goober

  Scenario I have a background worker in my application that runs off and does a bunch of processing. I specifically used this implementation so as to keep my User Interface fluid and prevent it from freezing up. I want to keep the background worker, but inside that thread, spawn off ONLY 3 MORE threads - making them share the processing (currently the worker thread just loops through and processes each asset one-by-one. However I would like to speed this up but using only a limited number of threads. Question Given the code below, how can I get the loop to choose a thread that is free, and then essentially wait if there isn't one free before it continues. CODE foreach (KeyValuePair<int, LiveAsset> kvp in laToHaganise) { Haganise h = new Haganise(kvp.Value, busDate, inputMktSet, outputMktSet, prodType, noOfAssets, bulkSaving); h.DoWork(); } Thoughts I'm guessing that I would have to start off by creating 3 new threads, but my concern is that if I'm instantiating a new Haganise object each time - how can I pass the correct "h" object to the correct thread..... Thread firstThread = new Thread(new ThreadStart(h.DoWork)); Thread secondThread =new Thread(new ThreadStart(h.DoWork)); Thread thirdThread = new Thread(new ThreadStart(h.DoWork)); Help greatly appreciated.

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• What is SSIS order of data transformation component method calls

  - by Ron Ruble

  I am working on a custom data transformation component. I'm using NUnit and NMock2 to test as I code. Testing and getting the custom UI and other features right is a huge pain, in part because I can't find any documentation about the order in which SSIS invokes methods on the component at design time as well as runtime. I can correct the issues readily enough, but it's tedious and time consuming to unregister the old version, register the new version, fire up the test ssis package, try to display the UI, get an obscure error message, backtrace it, modify the component and continue. One of the big issues involves the UI component needing access to the componentmetadata and buffermanager properties of the component at design time, and what I need to provide for to support properties that won't be initialized until after the user enters them in the UI. I can work through it; but if someone knows of some docs or tips that would speed me up, I'd greatly appreciate it. The samples I've found havn't been much use; they seem to be directed to showing off cool stuff (Twitter, weather.com) rather than actual work. Thanks in advance.

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• How to Manage CSS Explosion

  - by Jason

  I have been heavily relying on CSS for a website that I am working on (currently, everything is done as property values within each tag on the website and I'm trying to get away from that to make updates significantly easier). The problem I am running into, is I'm starting to get a bit of "CSS explosion" going on. It is becoming difficult for me to decide how to best organize and abstract data within the CSS file. For example: I am using a large number of div tags within the website (previously it was completely tables based). So I'm starting to get a lot of CSS that looks like this... div.title { background-color: Blue; color: White; text-align: center; } div.footer { /* Stuff Here */ } div.body { /* Stuff Here */ } etc. It's not too bad yet, but since I am learning here, I was wondering if recommendations could be made on how best to organize the various parts of a CSS file. What I don't want to get to is where I have a separate CSS attribute for every single thing on my website (which I have seen happen), and I always want the CSS file to be fairly intuitive. (P.S. I do realize this is a very generic, high-level question. My ultimate goal is to make it easy to use the CSS files and demonstrate their power to increase the speed of web development so other individuals that may work on this site in the future will also get into the practice of using them rather than hard-coding values everywhere.)

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• Android ANR keyDispatchingTimedOut Error while continuous tapping on screen.

  - by user519846

  Hi All, I am getting Application Not Responding (ANR) dialog while continuous tapping on the screen. There is no view on the screen where i am tapping. Frequency of this issue is less but still i am not able to remove it completely. Here i am attaching the log what i caught during this error. ERROR/ActivityManager(1322): ANR in com.test.mj.and.ui (com.test.mj.and.ui/.TermsAndCondActivity) ERROR/ActivityManager(1322): Reason: keyDispatchingTimedOut ERROR/ActivityManager(1322): Parent: com.test.mj.and.ui/.SplashActivity ERROR/ActivityManager(1322): Load: 6.59 / 6.37 / 5.21 ERROR/ActivityManager(1322): CPU usage from 11430ms to 2196ms ago: ERROR/ActivityManager(1322): rtal.mj.and.ui: 9% = 7% user + 1% kernel / faults: 649 minor ERROR/ActivityManager(1322): system_server: 4% = 2% user + 2% kernel / faults: 10 minor ERROR/ActivityManager(1322): logcat: 3% = 1% user + 1% kernel / faults: 675 minor 1 major ERROR/ActivityManager(1322): synaptics_wq: 1% = 0% user + 1% kernel ERROR/ActivityManager(1322): ami304d: 1% = 0% user + 0% kernel ERROR/ActivityManager(1322): .process.lghome: 1% = 0% user + 0% kernel / faults: 47 minor ERROR/ActivityManager(1322): sync_supers: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): droid.DunServer: 0% = 0% user + 0% kernel / faults: 6 minor ERROR/ActivityManager(1322): events/0: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): oid.inputmethod: 0% = 0% user + 0% kernel / faults: 2 minor ERROR/ActivityManager(1322): m.android.phone: 0% = 0% user + 0% kernel / faults: 2 minor ERROR/ActivityManager(1322): ndroid.settings: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): sh: 0% = 0% user + 0% kernel / faults: 110 minor ERROR/ActivityManager(1322): -flush-179:0: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): TOTAL: 19% = 13% user + 6% kernel WARN/WindowManager(1322): Continuing to wait for key to be dispatched WARN/WindowManager(1322): No window to dispatch pointer action 1 Can anyone please help me to solve this issue? Thanks in advance.

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• Python Turtle Graphics, how to plot functions over an interval?

  - by TheDragonAce

  I need to plot a function over a specified interval. The function is f1, which is shown below in the code, and the interval is [-7, -3]; [-1, 1]; [3, 7] with a step of .01. When I execute the program, nothing is drawn. Any ideas? import turtle from math import sqrt wn = turtle.Screen() wn.bgcolor("white") wn.title("Plotting") mypen = turtle.Turtle() mypen.shape("classic") mypen.color("black") mypen.speed(10) while True: try: def f1(x): return 2 * sqrt((-abs(abs(x)-1)) * abs(3 - abs(x))/((abs(x)-1)*(3-abs(x)))) * \ (1 + abs(abs(x)-3)/(abs(x)-3))*sqrt(1-(x/7)**2)+(5+0.97*(abs(x-0.5)+abs(x+0.5))-\ 3*(abs(x-0.75)+abs(x+0.75)))*(1+abs(1-abs(x))/(1-abs(x))) mypen.penup() step=.01 startf11=-7 stopf11=-3 startf12=-1 stopf12=1 startf13=3 stopf13=7 def f11 (startf11,stopf11,step): rc=[] y = f1(startf11) while y<=stopf11: rc.append(startf11) #y+=step mypen.setpos(f1(startf11)*25,y*25) mypen.dot() def f12 (startf12,stopf12,step): rc=[] y = f1(startf12) while y<=stopf12: rc.append(startf12) #y+=step mypen.setpos(f1(startf12)*25, y*25) mypen.dot() def f13 (startf13,stopf13,step): rc=[] y = f1(startf13) while y<=stopf13: rc.append(startf13) #y+=step mypen.setpos(f1(startf13)*25, y*25) mypen.dot() f11(startf11,stopf11,step) f12(startf12,stopf12,step) f13(startf13,stopf13,step) except ZeroDivisionError: continue

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• Android - I can't make a widget clickable to launch an intent

  - by Daniele

  Hi all. I am new to Android development. I have developed a very simple widget that was meant to interact with the user via an ImageButton. What I am trying to do now is as follows. When a user taps the button (after adding the widget to their home screen), I want the phone to dial a certain telephone number. A sort of speed dial for your home screen. Unfortunately when I tap the button nothing happens. This is the body of my SpeedDialAppWidgetProvider.onUpdate method: Log.d("", "beginning of onUpdate"); final int N = appWidgetIds.length; for (int i=0; i<N; i++) { int appWidgetId = appWidgetIds[i]; Log.d("", "dealing with appWidgetId: " + appWidgetId); // Create an Intent to launch ExampleActivity Intent dialIntent = new Intent(Intent.ACTION_CALL, Uri.parse("tel:1234567")); PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, dialIntent, 0); Log.d("", "pendingIntent classname " + pendingIntent.getClass().getName()); // Get the layout for the App Widget and attach an on-click listener to the button RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.speed_dial_appwidget); remoteViews.setOnClickPendingIntent(R.id.dial_icon, pendingIntent); Log.d("", "remoteViews classname " + remoteViews.getClass().getName()); // Tell the AppWidgetManager to perform an update on the current App Widget appWidgetManager.updateAppWidget(appWidgetId, remoteViews); Log.d("", "end of onUpdate"); I can see the method is called and the result of the logging makes sense. The speed_dial_appwidget.xml file is like this: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" androidrientation="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content" > <ImageButton id="@+id/dial_icon" android:src="@drawable/speed_dial" android:layout_width="wrap_content" android:layout_height="wrap_content"/> </LinearLayout> Can you please help me with this? Thanks in advance, Dan

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• Run a PHP script every second using CLI

  - by Saif Bechan

  Hello, I have a dedicated server running Cent OS with a Parallel PLESK panel. I need to run a php script every second, that updates my database. These is no alternative way timewise, i have checked every method, it needs to be updated every second. I can find my script using the url: http://www.mysite.com/phpfile.php?key=123, and this has to be executed every second. Does anyone have any knowledge at all on doing this, i can not seem to find the answer. I heard about doing it with CLI and putty, but i have no knowledge of this at all. Or can this be done using the PLESK Panel? And can the file be executed locally every second. Like \phpfile.php If someone helps me on answering these question i would really appreciate it. Regards EDIT It has been a few months since i added this question. I ended up using the following code: #!/user/bin/php $start = microtime(true); set_time_limit(60); for (i = 0; i < 59; ++$i) { doMyThings(); time_sleep_until($start + $i + 1); } Thank you for this code guys! My cronjob is set to every minute. I have been running this for some time now in a test environment, and this works out great. It works really supperfast, and i see no increase in CPU nor Memory usage.

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• Improve Application Performace

  - by Gtest

  Hello, Want To Improvide Performace Of C#.Net Applicaiton.. In My Application I am using Third Party Interop/Dll To Process .doc Files. It's a Simple Operation, Which Pass Input/Output FilePath to Interop dll ...& dll will execute text form input file. To Improve Performace I have Tried, Execute 2 therad to process 32 files.(each Thread process 16 files) Execute application code by creating 2 new AppDomains(each AppDomain Code process 16 files) Execute Code Using TPL(Task Parellel Library) But all options take around same time (32 sec) to process 32 files.Manually process tooks same 32 sec to process 32 files. Just tried one thing ..when i have created sample exe to process 16 files as input & output for refrence PAth given in TextBox. ..I open 2 exe instance to process. 1 exe has differnt 16 input files & output Created with input file path 2 exe has differnt 16 input files & output Created with input file path When i click on start button of both exe ..it use 100% cpu & Utilize both core significantly & Process Completed within 16 sec for 32 files. Can we provide this kind of explicit prallism to Improve my applicaiton Peformace? Thanks.

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• Performance of Java matrix math libraries?

  - by dfrankow

  We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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• How can I make this method more Scalalicious

  - by Neil Chambers

  I have a function that calculates the left and right node values for some collection of treeNodes given a simple node.id, node.parentId association. It's very simple and works well enough...but, well, I am wondering if there is a more idiomatic approach. Specifically is there a way to track the left/right values without using some externally tracked value but still keep the tasty recursion. /* * A tree node */ case class TreeNode(val id:String, val parentId: String){ var left: Int = 0 var right: Int = 0 } /* * a method to compute the left/right node values */ def walktree(node: TreeNode) = { /* * increment state for the inner function */ var c = 0 /* * A method to set the increment state */ def increment = { c+=1; c } // poo /* * the tasty inner method * treeNodes is a List[TreeNode] */ def walk(node: TreeNode): Unit = { node.left = increment /* * recurse on all direct descendants */ treeNodes filter( _.parentId == node.id) foreach (walk(_)) node.right = increment } walk(node) } walktree(someRootNode) Edit - The list of nodes is taken from a database. Pulling the nodes into a proper tree would take too much time. I am pulling a flat list into memory and all I have is an association via node id's as pertains to parents and children. Adding left/right node values allows me to get a snapshop of all children (and childrens children) with a single SQL query. The calculation needs to run very quickly in order to maintain data integrity should parent-child associations change (which they do very frequently). In addition to using the awesome Scala collections I've also boosted speed by using parallel processing for some pre/post filtering on the tree nodes. I wanted to find a more idiomatic way of tracking the left/right node values. After looking at the answers listed I have settled on this synthesised version: def walktree(node: TreeNode) = { def walk(node: TreeNode, counter: Int): Int = { node.left = counter node.right = treeNodes .filter( _.parentId == node.id) .foldLeft(counter+1) { (counter, curnode) => walk(curnode, counter) + 1 } node.right } walk(node,1) }

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• How to access C arrays from assembler for Windows x64?

  - by 0xdword32

  I've written an assembler function to speed up a few things for image processing (images are created with CreateDIBSection). For Win32 the assembler code works without problems, but for Win64 I get a crash as soon as I try to access my array data. I put the relevant info in a struct and my assembler function gets a pointer to this struct. The struct pointer is put into ebx/rbx and with indexing I read the data from the struct. Any idea what I am doing wrong? I use nasm together with Visual Studio 2008 and for Win64 I set "default rel". C++ code: struct myData { tUInt32 ulParam1; void* pData; }; CallMyAssemblerFunction(&myData); Assembler Code: Win32: ... push ebp; mov ebp,esp mov ebx, [ebp + 8]; pointer to our struct mov eax, [ebx]; ulParam1 mov esi, [ebx + 4]; pData, 4 byte pointer movd xmm0, [esi]; ... Win64: ... mov rbx, rcx; pointer to our struct mov eax, [rbx]; ulParam1 mov rsi, [rbx + 4]; pData, 8 byte pointer movd xmm0, [rsi]; CRASH! ...

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• Problem when getting pageContent of an unavailable URL in Java

  - by tiendv

  I have a code for get pagecontent from a URL: import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.net.URLConnection; public class GetPageFromURLAction extends Thread { public String stringPageContent; public String targerURL; public String getPageContent(String targetURL) throws IOException { String returnString=""; URL urlString = new URL(targetURL); URLConnection openConnection = urlString.openConnection(); String temp; BufferedReader in = new BufferedReader( newInputStreamReader(openConnection.getInputStream())); while ((temp = in.readLine()) != null) { returnString += temp + "\n"; } in.close(); // String nohtml = sb.toString().replaceAll("\\<.*?>",""); return returnString; } public String getStringPageContent() { return stringPageContent; } public void setStringPageContent(String stringPageContent) { this.stringPageContent = stringPageContent; } public String getTargerURL() { return targerURL; } public void setTargerURL(String targerURL) { this.targerURL = targerURL; } @Override public void run() { try { this.stringPageContent=this.getPageContent(targerURL); } catch (IOException e) { e.printStackTrace(); } } } Sometimes I receive an HTTP error of 405 or 403 and result string is null. I have tried checking permission to connect to the URL with: URLConnection openConnection = urlString.openConnection(); openConnection.getPermission() but it usualy returns null. Does mean that i don't have permission to access the link? I have tried stripping off the query portion of the URL with: String nohtml = sb.toString().replaceAll("\\<.*?>",""); where sb is a Stringbulder, but it doesn't seem to strip off the whole query substring. In an unrelated question, I'd like to use threads here because I must retrieve many URLs; how can I create a multi-thread client to improve the speed?

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• Testing performance of queries in mysl

  - by Unreason

  I am trying to setup a script that would test performance of queries on a development mysql server. Here are more details: I have root access I am the only user accessing the server Mostly interested in InnoDB performance The queries I am optimizing are mostly search queries (SELECT ... LIKE '%xy%') What I want to do is to create reliable testing environment for measuring the speed of a single query, free from dependencies on other variables. Till now I have been using SQL_NO_CACHE, but sometimes the results of such tests also show caching behaviour - taking much longer to execute on the first run and taking less time on subsequent runs. If someone can explain this behaviour in full detail I might stick to using SQL_NO_CACHE; I do believe that it might be due to file system cache and/or caching of indexes used to execute the query, as this post explains. It is not clear to me when Buffer Pool and Key Buffer get invalidated or how they might interfere with testing. So, short of restarting mysql server, how would you recommend to setup an environment that would be reliable in determining if one query performs better then the other?

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• Temporary storage for keeping data between program iterations?

  - by mr.b

  I am working on an application that works like this: It fetches data from many sources, resulting in pool of about 500,000-1,500,000 records (depends on time/day) Data is parsed Part of data is processed in a way to compare it to pre-existing data (read from database), calculations are made, and stored in database. Resulting dataset that has to be stored in database is, however, much smaller in size (compared to original data set), and ranges from 5,000-50,000 records. This process almost always updates existing data, perhaps adds few more records. Then, data from step 2 should be kept somehow, somewhere, so that next time data is fetched, there is a data set which can be used to perform calculations, without touching pre-existing data in database. I should point out that this data can be lost, it's not irreplaceable (key information can be read from database if needed), but it would speed up the process next time. Application components can (and will be) run off different computers (in the same network), so storage has to be reachable from multiple hosts. I have considered using memcached, but I'm not quite sure should I do so, because one record is usually no smaller than 200 bytes, and if I have 1,500,000 records, I guess that it would amount to over 300 MB of memcached cache... But that doesn't seem scalable to me - what if data was 5x that amount? If it were to consume 1-2 GB of cache only to keep data in between iterations (which could easily happen)? So, the question is: which temporary storage mechanism would be most suitable for this kind of processing? I haven't considered using mysql temporary tables, as I'm not sure if they can persist between sessions, and be used by other hosts in network... Any other suggestion? Something I should consider?

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