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  • Which library should I use for server-side image manipulation on Node.JS?

    - by Andrew
    I found a quite large list of available libraries on Node.JS wiki but I'm not sure which of those are more mature and provide better performance. Basically I want to do the following: load some images to a server from external sources put them onto one big canvas crop and mask them a bit apply a filter or two Resize the final image and give a link to it Big plus if the node package works on both Linux and Windows.

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  • Should I amortize scripting cost via bytecode analysis or multithreading?

    - by user18983
    I'm working on a game sort of thing where users can write arbitrary code for individual agents, and I'm trying to decide the best way to divide up computation time. The simplest option would be to give each agent a set amount of time and skip their turn if it elapses without an action being decided upon, but I would like people to be able to write their agents decision functions without having to think too much about how long its taking unless they really want to. The two approaches I'm considering are giving each agent a set number of bytecode instructions (taking cost into account) each timestep, and making players deal with the consequences of the game state changing between blocks of computation (as with Battlecode) or giving each agent it's own thread and giving each thread equal time on the processor. I'm about equally knowledgeable on both concurrency and bytecode stuff, which is to say not very, so I'm wondering which approach would be best. I have a clearer idea of how I'd structure things if I used bytecode, but less certainty about how to actually implement the analysis. I'm pretty sure I can work up a concurrency based system without much trouble, but I worry it will be messier with more overhead and will add unnecessary complexity to the project.

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  • Prevent query string manipulation by adding a hash?

    - by saille
    To protect a web application from query string manipulation, I was considering adding a query string parameter to every url which stores a SHA1 hash of all the other query string parameters & values, then validating against the hash on every request. Does this method provide strong protection against user manipulation of query string values? Are there any other downsides/side-effects to doing this? I am not particularly concerned about the 'ugly' urls for this private web application. Url's will still be 'bookmarkable' as the hash will always be the same for the same query string arguments. This is an ASP.NET application.

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  • How does Google App Engine precompile Java ?

    - by Thilo
    App Engine uses a "precompilation" process with the Java bytecode of an app to enhance the performance of the app in the Java runtime environment. Precompiled code functions identically to the original bytecode. Is there any detailed information what this does?

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  • Draw images with warped triangles on a web server [migrated]

    - by epologee
    The scenario The Flash front end of my current project produces images that a web server needs to combine into a video. Both frame-rate and frame-resolution are sizeable enough that sending an image sequence to the back end is not feasible (in both time and client bandwidth). Instead, we're trying to recreate the image drawing on the back end as well. Correct and slow, or incorrect and fast The problem is that this involves quite a bit of drawing textured triangles, and two solutions we found in Python (here and there) are so inefficient, that the drawing takes about 60 seconds per frame, resulting in a whopping 7,5 hours of processing time for a 30 second clip. Unacceptable. When using a PHP-module to send commands to ImageMagick for image manipulation, the whole process is super fast (tenths of a second per frame), but ImageMagick seems to be unable to draw triangles the way we do it in the front end, so the final results do not match. Unacceptable. What I'm asking here, is if there's someone who would know a way to solve this issue, by any means necessary that would run on a web server. Warping an image Let me explain the process of the front end: Perform a Delaunay calculation on points in an image to get an evenly distributed mesh of triangles. Offset the points/vertices in the mesh, distorting or warping the image. Draw the warped triangles on a new bitmap. We can send the results (coordinates) of steps 1 and 2 to the back end, to then draw the warped triangles and save it to an image on disk (or append as a frame to the video). But that last step is what I need help with. The Question Is there an alternative to ImageMagick that can draw triangles in a bitmap? Is there some other library, like a C library, that would allow us to do this? Or could we achieve this effect more easily by switching back end technologies, like Ruby? (.Net and Java are, unfortunately, not really options right now) Many thanks. EP. P.S. I'd appreciate re-tagging efforts, I don't quite know what labels to put on this question. Thanks!

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  • Bulk retrieval in HQL: could not execute native bulk manipulation query

    - by user179056
    Hello, We are getting a "could not execute native bulk manipulation query" error in HQL When we execute a query which is something like this. String query = "Select person.id from Person person where"; String bindParam = ""; List subLists = getChucnkedList(dd); for(int i = 0 ; i < subLists.size() ;i++){ bindParam = bindParam + " person.id in (:param" + i + ")"; if (i < subLists.size() - 1 ) { bindParam = bindParam + " OR " ; } } query = query + bindParam; final Query query1 = session.createQuery(query.toString()); for(int i = 0 ; i < subLists.size() ;i++){ query1.setParameterList("param" + i, subLists.get(i)); } List personIdsList = query1.list(); Basically to avoid the limit on IN clause in terms of number of ids which can be inserted (not more than 1000), we have created sublists of ids of not more than 1000 in number. We are using bind parameters to bind each sublist. However we still get error "could not execute native bulk manipulation query" How does one avoid the problem of limited parameters possible in IN query when parameters passed are more than 1000? regards Sameer

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  • C++ to bytecode compiler for CLR?

    - by paleozogt
    I'd like to be able to compile a C++ library so that it runs within a managed runtime in the CLR. There are several tools for doing this with the JVM (NestedVM, LLJVM, etc) but I can't seem to find any for the CLR. Has anyone tried doing this?

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  • C++ to bytecode compiler for Silverlight CLR?

    - by paleozogt
    I'd like to be able to compile a C/C++ library so that it runs within a safe managed runtime in the Silverlight CLR. There are several tools for doing this with the JVM that allows C++ code to run within a CRT emulation layer (see NestedVM, LLJVM, etc), which effectively allows C++ code to be run within a Java Applet. There's even a tool for this for the Adobe Flash VM (see Alchemy). However, I can't seem to find any tools like this for the CLR. fyi, the MSVC tools don't seem to allow for this: The /clr:pure flag will create C++ code that runs in the CLR, but it isn't safe (because the CRT isn't safe) and /clr:safe requires massive code changes (no native types, etc).

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  • PHP – Slow String Manipulation

    - by Simon Roberts
    I have some very large data files and for business reasons I have to do extensive string manipulation (replacing characters and strings). This is unavoidable. The number of replacements runs into hundreds of thousands. It's taking longer than I would like. PHP is generally very quick but I'm doing so many of these string manipulations that it's slowing down and script execution is running into minutes. This is a pain because the script is run frequently. I've done some testing and found that str_replace is fastest, followed by strstr, followed by preg_replace. I've also tried individual str_replace statements as well as constructing arrays of patterns and replacements. I'm toying with the idea of isolating string manipulation operation and writing in a different language but I don't want to invest time in that option only to find that improvements are negligible. Plus, I only know Perl, PHP and COBOL so for any other language I would have to learn it first. I'm wondering how other people have approached similar problems? I have searched and I don't believe that this duplicates any existing questions.

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  • JAVA bytecode optimization

    - by Idob
    This is a basic question. I have code which shouldn't run on metadata beans. All metadata beans are located under metadata package. Now, I use reflection API to find out whether a class is located in the the metadata package. if (newEntity.getClass().getPackage().getName().contains("metadata")) I use this If in several places within this code. The question is: Should I do this once with: boolean isMetadata = false if (newEntity.getClass().getPackage().getName().contains("metadata")) { isMetadata = true; } C++ makes optimizations and knows that this code was already called and it won't call it again. Does JAVA makes optimization? I know reflection API is a beat heavy and I prefer not to lose expensive runtime.

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  • Remember JVM state before executing a specific instruction.

    - by user559064
    I am working on a testing project using mutating technique. My project requires to manipulate a Java classfile and re-execute the classfile multiple times for testing. My implementation need to re-execute the whole system again after one manipulation, and that is not efficient. I am wondering whether I can save the JVM state right before executing a desired instruction in the classfile, so that I can start from that state after each manipulation. Thank you.

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  • automatic manipulation of email messages

    - by Toc
    Does it exist any web service that "filters" any email message allowing to change the subject or the content on a regexp basis and then forward it to my webmail address? For example: I want to append automatically the string "IMPORTANT! " to the subject of every message I receive with the subject containing "expiry", or I want to change any occurrence of "h2" in the body to "h1".

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  • Slow manipulation of netfilter rules

    - by Ole Martin Eide
    I have a script maintaining gre tunnels and firewall rules using the "ip" and "iptables" tools. Setting up hundreds of tunnels, and adresses per interface runs just fine. Takes less than 0.1 second per interface, however when I get around to do the firewall rules everything slows down spending 0.5 per insertion. Why is it running so slow? What can I do to improve the speed? It seems like I could try ipset instead, but I really feel there is something wrong with the kernel or something. The interesting thing is that the first 10 rules runs fast, then it slows down.. mybox(root) foo# iptables -V iptables v1.3.5 mybox(root) foo# uname -a Linux foo 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux mybox(root) foo# cat test.sh #!/bin/sh for n in {1..100} do /sbin/iptables -A OUTPUT -s ${n} -j ACCEPT /sbin/iptables -D OUTPUT -s ${n} -j ACCEPT done mybox(root) foo# time ./test.sh real 1m38.839s user 0m0.100s sys 1m38.724s Appriciate any help. Cheers!

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  • PHP Color Manipulation

    - by Lizard
    I am currently looking into color manipulation / selection etc and have come acroos the following piece of code. I was wondering of someone could tell me what the following piece of code is doing and break it down for me thanks! $newVal = round(round(($rgb['red'] / 0x33)) * 0x33); In particluar what is the 0x33 Thanks in adavnce

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  • Does visibility affect DOM manipulation performance?

    - by Chetan Sastry
    IE7/Windows XP I have a third party component in my page that does a lot of DOM manipulation to adjust itself each time the browser window is resized. Unfortunately I have little control of what it does internally and I have optimized everything else (such as callbacks and event handlers) as much as I can. I can't take the component off the flow by setting display:none because it fails measuring itself if I do so. In general, does setting visibility of the container to invisible during the resize help improve DOM rendering performance?

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  • xpath: string manipulation

    - by Jindan Zhou
    So in my scrapy project I was able to isolate some particular fields, one of the field return something like: [Rank Info] on 2013-06-27 14:26 Read 174 Times which was selected by expression: (//td[@class="show_content"]/text())[4] I usually do post-processing to extract the datetime information, i.e., 2013-06-27 14:26 Now since I've learned a little more on the xpath substring manipulation, I am wondering if it is even possible to extract that piece of information in the first place, i.e., in the xpath expression itself? Thanks,

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  • R or Python for file manipulation

    - by danspants
    I have 4 reasonably complex r scripts that are used to manipulate csv and xml files. These were created by another department where they work exclusively in r. My understanding is that while r is very fast when dealing with data, it's not really optimised for file manipulation. Can I expect to get significant speed increases by converting these scripts to python? Or is this something of a waste of time?

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  • High speed matrix manipulation in c#?

    - by Donnie
    I'm working on some image manipulation code in c# and need to do some matrix operations (specifically 2D convolution). I have the code written in matlab which uses the conv2 function ... is there a library for C# / .NET that does good high-speed matrix manipulations? I'd be fine if it requires some specific GPU and does the matrix math on-GPU if that's what it takes.

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  • Does Java support dynamic method invocation?

    - by eSKay
    class A { void F() { System.out.println("a"); }} class B extends A { void F() { System.out.println("b"); }} public class X { public static void main(String[] args) { A objA = new B(); objA.F(); } } Here, F() is being invoked dynamically, isn't it? This article says ... the Java bytecode doesn’t support dynamic method invocation. There are three supported invocations modes : invokestatic, invokespecial, invokeinterface or invokevirtual. These modes allows to call methods with known signature. We talk of strongly typed language. This allows to to make some checks directly at compile time. On the other side, the dynamic languages use dynamic types. So we can call a method unknown at the compile time, but that’s completely impossible with the Java bytecode. What am I missing?

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  • ctypes and pointer manipulation

    - by Chris
    I am dealing with image buffers, and I want to be able to access data a few lines into my image for analysis with a c library. I have created my 8-bit pixel buffer in Python using create_string_buffer. Is there a way to get a pointer to a location within that buffer without re-creating a new buffer? My goal is to analyze and change data within that buffer in chunks, without having to do a lot of buffer creation and data copying. In this case, ultimately, the C library is doing all the manipulation of the buffer, so I don't actually have to change values within the buffer using Python. I just need to give my C function access to data within the buffer.

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