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  • Java Convert ColorSpace of BufferedImage to CS_GRAY without using ConvertColorOp

    - by gmatt
    I know its possible to convert an image to CS_GRAY using public static BufferedImage getGrayBufferedImage(BufferedImage image) { BufferedImageOp op = new ColorConvertOp(ColorSpace .getInstance(ColorSpace.CS_GRAY), null); BufferedImage sourceImgGray = op.filter(image, null); return sourceImgGray; } however, this is a chokepoint of my entire program. I need to do this often, on 800x600 pixel images and takes about 200-300ms for this operation to complete, on average. I know I can do this alot faster by using one for loop to loop through the image data and set it right away. The code above on the other hand constructs a brand new 800x600 BufferedImage that is gray scale. I would rather just transform the image I pass in. Does any one know how to do this with a for loop and given that the image is RGB color space?

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  • Efficient calculation of matrix cumulative standard deviation in r

    - by Abiel
    I recently posted this question on the r-help mailing list but got no answers, so I thought I would post it here as well and see if there were any suggestions. I am trying to calculate the cumulative standard deviation of a matrix. I want a function that accepts a matrix and returns a matrix of the same size where output cell (i,j) is set to the standard deviation of input column j between rows 1 and i. NAs should be ignored, unless cell (i,j) of the input matrix itself is NA, in which case cell (i,j) of the output matrix should also be NA. I could not find a built-in function, so I implemented the following code. Unfortunately, this uses a loop that ends up being somewhat slow for large matrices. Is there a faster built-in function or can someone suggest a better approach? cumsd <- function(mat) { retval <- mat*NA for (i in 2:nrow(mat)) retval[i,] <- sd(mat[1:i,], na.rm=T) retval[is.na(mat)] <- NA retval } Thanks.

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  • System.XML or Regex.Replace?

    - by cam
    I'm generating a large amount of XML documents from a set of values in an Excel file. The only thing that changes for each XML document is the values. I figured the best way to generate these documents was to make a "XML skeleton" (since the XML format never changes) and then plug in symbols like "&%blahNameblahTest", so then I could just preform a Regex.Replace on each value. I will be handing over this project to another developer and I'm wondering if I should convert the project to generate the XML file manually everytime through the System.XML namespace. The only advantages I see to this is ensuring that the XML document is valid. The current method would be more readable than that method, and way faster since I'm generating around 1500 documents.

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  • PHP Thumbnail image generator works, but consistently awaits 90% of its loadtime! Why?

    - by Sam
    Hi folks, This is the follow-up question from this general page load speed question. This question which will focus only, entirely and specifically on the thumbnail generator PHP code with the question: What's causing the 97% delays on these tiny thumbnails? Measuring only 3 ~ 5 kb each, this is strange indeed! Even after 7 orso bounty-rounds and 100 upvotes, the images are still doing nothing for over 97% of the time. It works allright, but it could be so much faster! ZAM, my pet robot, was so annoyed by not knowing why, he just pulled out some cords! Silly metal box... (I have asked permission from the original author, to put temporarily segments of the code online that I think could be the problem, after which I will remove all code, except the several lines that were the direct cause of this issue here to match the answer. This will be the free opportunity to perfect/speedup his otherwise already to my opinion vert versatile and userfriendly thumbnail generator.)

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  • Smooth table view like on iPod.app

    - by Gilo
    Hey folks ;), Im trying to redo the table view in the ipod.app. The one with 2 labels and the cover on the left. I want the same information there. I mean the cover plus all the other MPMediaItem stuff. Everything works fine. I can build the table and get all the information from the music library I need. My only problem is that my table is far away from being smooth. It lacks. When I remove the MPMediaArtworkItem from the table its super fast. So I guess its a problem with that. Is there any way to load the MPMediaProperties more faster? Whats the fastest way? THX in advance :)

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  • Socket ping-pong performance

    - by Kamil_H
    I have written two simple programs (tried it in C++ and C#). This is pseudo code: -------- Client --------------- for(int i = 0; i < 200.000; i++) { socket_send("ping") socket_receive(buff) } --------- Server ------------- while(1) { socket_receive(buff) socket_send("pong") } I tried it on Windows. Execution time of client is about 45 seconds. Can somebody explain me why this takes so long? I understand that if there were real network connection between client and server the time of one 'ping-pong' would be: generate_ping + send_via_network + generate_pong + send_via_network but here everything is done in 'local' mode. Is there any way to make this inter process ping-pong faster using network sockets (I'm not asking about shared memory for example :) )

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  • In SQL, in what situation do we want to Index a field in a table, or 2 fields in a table at the same

    - by Jian Lin
    In SQL, it is obvious that whenever we want to do a search on millions of record, say CustomerID in a Transactios table, then we want to add an index for CustomerID. Is another situation we want to add an index to a field when we need to do inner join or outer join using that field as a criteria? Such as Inner join on t1.custumerID = t2.customerID. Then if we don't have an index on customerID on both tables, we are looking at O(n^2) because we need to loop through the 2 tables sequentially. If we have index on customerID on both tables, then it becomes O( (log n) ^ 2 ) and it is much faster. Any other situation where we want to add an index to a field in a table? What about adding index for 2 fields combined in a table. That is, one index, for 2 fields together?

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  • Fastest way of creating XML from parent-child table in c#?

    - by rudnev
    Assume we have some DataTable or IEnumerable with ChildID, ParentID and Title. We need to serialize it to XML like <Entity title=""> <Entity title=""></Entity> <Entity title=""></Entity> </Entity> As i found out, standard DataTable.GetXML() returns something different. I thought about initializing class tree like Entity e = new Entity(ID, Title, ParentEntityID) and then serializing it. Table is about 3000 elems. Is there faster way?

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  • DB4o Linq query - How to check for null strings

    - by Dave
    Hey there - simple query: var q = (from SomeObject o in container where o.SomeInt > 8 && o.SomeString != null //Null Ref here select o; I always get a null reference exception. If I use String.IsNullOrEmpty(o.SomeString) the query takes about 100 times as long, as if I use && o.SomeString != "" (which is way faster, but obviously not correct). I'm guessing because DB4o needs to activate the objects, in order to pass them in to the IsNullOrEmpty call, and can't use the indexes. My question is, what's a better way to check for nulls in this situation? Is there something like: mystring != Db4o.DBNull.Value, or something? Cheers, Dave

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  • crunching multiple js files during development

    - by Yaron Naveh
    I'm writing a backbone.js app. I have multiple js, css and html template files. I also have a script to crunch them into a single file so it is faster to download. How should I work during development: Add a listener to the file system and after every change compile the files so I can see it in a browser. This implies a 1-2 seconds overhead before I can see what I did, which is annoying for html fine-tuning. Somehow browse using the multiple files during development and only crunch before going to production. This means I need to have a separate index.html for dev and prod. What's your take?

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  • Will Multi threading increase the speed of the calculation on Single Processor

    - by Harsha
    On a single processor, Will multi-threading increse the speed of the calculation. As we all know that, multi-threading is used for Increasing the User responsiveness and achieved by sepating UI thread and calculation thread. But lets talk about only console application. Will multi-threading increases the speed of the calculation. Do we get culculation result faster when we calculate through multi-threading. what about on multi cores, will multi threading increse the speed or not. Please help me. If you have any material to learn more about threading. please post. Thanks in advance, Harsha

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  • What are the main benefits of implementing a virtual machine as part of an application?

    - by Marplesoft
    Several databases I've been looking at recently implement a virtual machine internally to perform the respective data reads and writes. For an example, check out this article on SQLite's virtual machine they call the 'VDBE'. I'm curious as to what the benefits of such an architecture are. I would assume performance is one but why would a virtual machine like this run faster? In fact, it seems to be that this extra layer could cause it to run slower. So perhaps it's for security? Or portability? Anyway, just curious about this.

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  • Is it magic or what ??

    - by STRIDER
    I am writing a big C code... The code includes recursive bactracking function named Branch() that is called so much... My goal is to write the fastest code to get the best running time... I also have another function Redundant() void Redundant() { int* A; A=(int*)malloc(100*sizeof(int)); } I created two versions. Version A: Redundant() is included in Branch(). Version B: Redundant() is not included in Branch() A run 10 times faster than B !!!! Is is Magic or is it kind of process scheduling or what ??

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  • Will VC++ MFC become obsolete in near future?

    - by AKN
    Normally people say MFC is little clumsy. It makes UI development slightly difficult to maintain since it has lot of auto generated code. It has good architecture (doc/view) but is not transparent like Win32 programming to understand how window program works in the background. So with this situation, is it good to extend the exposure on MFC programming or better to switch to .NET since for faster UI design with ease in maintenance. Is it good to continue as MFC developer or good to know .NET as well? How globally companies are looking into MFC as a technology for UI developments. Are they comfortable in supporting their developers to continue with MFC or looking for changing their development technology.

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  • Slow Speeds when unzipping with PHP onto a NFS, how can I speed it up?

    - by bunwich
    Hi, I'm trying to figure out how to boost my NFS speed and php uploads. File is uploaded to the webserver's local tmp dir With PHP I copy the file userxxx.zip to the NFS With PHP I extract the userxxx.zip on the NFS to another dir on the NFS. What I'm finding is the file is in Step 3, the file is being read through the NFS by the web server, processed by the web server, and uploaded back across the NFS. Speeds as expected are very slow. Might a possible solution be to get the Fileserver to extract the zip? a) Webserver copies the file to the NFS b) Webserver makes a web service call to the Fileserver c) Fileserver can now unzip the file like it's local and the speeds should be much faster. I would appreciate any suggestion anyone how people have approached this problem. (I'm aware that php ZipArchive() is very slow, and I'll likely use java or php exec unzip to speed it up) Thanks

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  • Quickly retrieve the subset of properties used in a huge collection in C#

    - by ccornet
    I have a huge Collection (which I can cast as an enumerable using OfType<()) of objects. Each of these objects has a Category property, which is drawn from a list somewhere else in the application. This Collection can reach sizes of hundreds of items, but it is possible that only, say, 6/30 of the possible Categories are actually used. What is the fastest method to find these 6 Categories? The size of the huge Collection discourages me from just iterating across the entire thing and returning all unique values, so is there a faster method of accomplishing this? Ideally I'd collect the categories into a List.

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  • Changing <img src="XXX" />, js event when new image has finished loading?

    - by carillonator
    I have a photo gallery web page where a single <img src="XXX" /> element's src is changed (on a click) with javascript to show the next image—a poor man's ajax I guess. Works great on faster connections when the new image appears almost immediately. Even if it takes a few seconds to load, every browser I've tested it on keeps the old image in place until the new one is completely loaded. It's a little confusing waiting those few seconds on a slow connection, though, and I'm wondering if there's some javascript event that fires when the new image is done loading, allowing me to put a little working... animated gif or something up in the meantime. I know I could use AJAX for real (I'm using jQuery already), but this is such a nice and simple solution. Besides this lag, is there any other reason I should stay away from this approach to changing images? thanks.

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  • iPhone: Interface Builder leaks memory?

    - by Stefan Klumpp
    I have been working on an iPhone project, where we created all the user interface programmatically in code. Now I'm going to start a new iPhone project and thinking of using Interface Builder instead, because it has been recommended to me as being a very useful tool, creating less headache than writing everything in code and in general much faster (regarding development time). However, my team members have some concerns due to previous problems with using Interface Builder and resulting memory leaks. Therefor they suggest building everything in code again. I don't know where these concerns come from, but maybe someone with more experience than we have can give some insight on that topic. Doing a simple Google search doesn't really provide any information proofing that there are any problems with memory leaks created by the Interface Builder itself.

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  • Redirecting user from an old web to another in Sharepoint

    - by BeraCim
    Hi all: I want to add the ability to redirect users when they visit certain old sites. The URL of the old sites are unknown, but the server name is the same, e.g. Old site url: http://sharepoint/mySite/default.aspx New site url: http://sharepoint/myNewSite/... There are a lot of other pages within mySite, most of which must be redirected to the new site, but there are exceptions (e.g. user can still view the documents within the site). I thought I have to do this programmatically by somehow capturing the http request and read the url myself. Being no sharepoint guru, I had a quick google, and found that writing a web part is prehaps the best alternative for my situation. But I'm just wondering, given my situation and needs, is writing a web part, or something programmatically, really the ideal solution? Or is there a faster and quicker way to achieve what I want using Sharepoint? Thanks.

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  • How to interpret mono profiler results?

    - by Ovidiu Pacurar
    I created a console application in C# and running it on windows/.NET is 5x faster than on linux/mono or windows/mono. The app encodes some binary files into text format(JSON). I profiled the app on linux/mono using: mono --profile=default:stat myconsoleapp.exe Here is the first part of the result: prof counts: total/unmanaged: 32274/25062 23542 72.95 % mono 459 1.42 % System.Decimal:Divide (System.Decimal,System.Decimal) 457 1.42 % System.Decimal:Round (System.Decimal,int,System.MidpointRounding) 411 1.27 % /lib/libz.so.1 262 0.81 % /lib/tls/i686/cmov/libc.so.6(memmove 253 0.78 % System.Decimal:IsZero () 247 0.77 % System.NumberFormatter:Init (string,double,int) 213 0.66 % System.NumberFormatter:AppendDigits (int,int) 72.95 % mono? Are mono internals using 3 quarters of the total execution time?

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  • Scaling larger Image problem.

    - by krishna
    Hi, I m developing flex application, in which I want to Draw Image from User local hard-drive to the canvas of size 640x360. User can choose Image of bigger resolution & is scaled to Canvas size. But if user selected images of larger resolution like 3000x2000, the scaling take lot time & freezes the application until scale done. Is there any method to scale image faster or kind of threading can be done? I am using matrix to scale Image as below: var mat:Matrix = new Matrix(); var scalex:Number = canvasScreen.width/content.width; var scaley:Number = canvasScreen.height/content.height; mat.scale(scalex,scaley); canvasScreen.graphics.clear(); canvasScreen.graphics.beginBitmapFill(content.bitmapData,mat);

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  • Endianness manipulation - is there a C library for this?

    - by Malvineous
    Hi all, With the sort of programs I write (working with raw file data) I often need functions to convert between big and little endian. Usually I write these myself (which is covered by many other posts here) but I'm not that keen on doing this for a number of reasons - the main one being lack of testing. I don't really want to spend ages testing my code in a big endian emulator, and often just omit the code for big endian machines altogether. I also would rather make use of faster functions provided by various compilers, while still keeping my programs cross-platform. The only things I can find are socket calls like htons() but they require different #include files on each platform, and some GPL code like this, however that particular file, while comprehensive, seems to miss out on some of the high performance functions provided by some compilers. So, does anyone know of a library (ideally just a .h file) that is well tested and provides a standard set of functions for dealing with endianness across many compilers and platforms?

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  • Single Large v/s Multiple Small MySQL tables for storing Options

    - by Prasad
    Hi there, I'm aware of several question on this forum relating to this. But I'm not talking about splitting tables for the same entity (like user for example) Suppose I have a huge options table that stores list options like Gender, Marital Status, and many more domain specific groups with same structure. I plan to capture in a OPTIONS table. Another simple option is to have the field set as ENUM, but there are disadvantages of that as well. http://www.brandonsavage.net/why-you-should-replace-enum-with-something-else/ OPTIONS Table: option_id <will be referred instead of the name> name value group Query: select .. from options where group = '15' - Since this table is expected to be multi-tenant, the no of rows could grow drastically. - I believe splitting the tables instead of finding by the group would be easier to write & faster to execute. - or perhaps partitioning by the group or tenant? Pl suggest. Thanks

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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  • Suppressing the language select button iPhone

    - by AWinter
    I'm working on an application now that contains an account register section. One field with secureTextEntry = NO (for registering only). The idea is this make registration faster and hopefully increases the number of signups. It's simple enough for me to just place a regular UITextField but if the user has any additional language keyboards then it's possible for the user to enter non-password friendly characters. Unlike in when secureTextEntry = YES. I know I can do textField.keyboardType = UIKeyboardTypeASCIICapable to get the text field to display the ASCII keyboard first, but the user will still have the keyboard switch button which will allow them to get to undesirable characters. Is there a simple method for suppressing the international button or forcing ASCII only keyboard with no international button? [EDIT] Another perhaps better option might be to suppress multi byte keyboards or even to display the text in the case that secureTextEntry = YES any ideas here? [EDIT AGAIN] I've decided it's a really bad idea to suppress the international button as non-multibyte characters should all be allowed.

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