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  • Will unused deconstructors be optimized out?

    - by Brendan Long
    Assuming MyClass uses the default deconstructor (or no deconstructor), and this code: MyClass buffer[] = new MyClass[i]; // Construct N objects using placement new for(size_t i = 0; i < N; i++){ ~buffer[i]; } delete[] buffer; Is there any optimizer that would be able to remove this loop? Also, is there any way for my code to detect if MyClass is using an empty/default constructor?

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  • PHP error handling : my code is not optimized

    - by Tristan
    Hello, I must warn you, this code will heart your eyes, so please don't judge me, i'm trying to improve the way I handle errors all my tests are like this : if ($something < 27) { $error_IP= '<div class="error_message">something bad</div> '; }else{ $erreur_IP=''; } and here's the ugliest thing : if( !isset($_POST) || ($erreur_captcha !='') || ($erreur_email !='') || ($erreur_hebergeurVide != '') || ($erreur_paysVide != '') || ($erreur_slotVide != '') || ($erreur_rconVide != '') || ($erreur_tick != '') + a lot more :d ) What do you suggest to me to optimize my errors handling ? Thank you

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  • Write file need to optimised for heavy traffic part 2

    - by Clayton Leung
    For anyone interest to see where I come from you can refer to part 1, but it is not necessary. write file need to optimised for heavy traffic Below is a snippet of code I have written to capture some financial tick data from the broker API. The code will run without error. I need to optimize the code, because in peak hours the zf_TickEvent method will be call more than 10000 times a second. I use a memorystream to hold the data until it reaches a certain size, then I output it into a text file. The broker API is only single threaded. void zf_TickEvent(object sender, ZenFire.TickEventArgs e) { outputString = string.Format("{0},{1},{2},{3},{4}\r\n", e.TimeStamp.ToString(timeFmt), e.Product.ToString(), Enum.GetName(typeof(ZenFire.TickType), e.Type), e.Price, e.Volume); fillBuffer(outputString); } public class memoryStreamClass { public static MemoryStream ms = new MemoryStream(); } void fillBuffer(string outputString) { byte[] outputByte = Encoding.ASCII.GetBytes(outputString); memoryStreamClass.ms.Write(outputByte, 0, outputByte.Length); if (memoryStreamClass.ms.Length > 8192) { emptyBuffer(memoryStreamClass.ms); memoryStreamClass.ms.SetLength(0); memoryStreamClass.ms.Position = 0; } } void emptyBuffer(MemoryStream ms) { FileStream outStream = new FileStream("c:\\test.txt", FileMode.Append); ms.WriteTo(outStream); outStream.Flush(); outStream.Close(); } Question: Any suggestion to make this even faster? I will try to vary the buffer length but in terms of code structure, is this (almost) the fastest? When memorystream is filled up and I am emptying it to the file, what would happen to the new data coming in? Do I need to implement a second buffer to hold that data while I am emptying my first buffer? Or is c# smart enough to figure it out? Thanks for any advice

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  • in java, which is better - three arrays of booleans or 1 array of bytes?

    - by joe_shmoe
    I know the question sounds silly, but consider this: I have an array of items and a labelling algorithm. at any point the item is in one of three states. The current version holds these states in a byte array, where 0, 1 and 2 represent the three states. alternatively, I could have three arrays of boolean - one for each state. which is better (consumes less memory) depends on how jvm (sun's version) stores the arrays - is a boolean represented by 1 bit? (p.s. don't start with all that "this is not the way OO/Java works" - I know, but here performance comes in front. plus the algorithm is simple and perfectly readable even in such form). Thanks a lot

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  • In ArrayBlockingQueue, why copy final member field into local final variable?

    - by mjlee
    In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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  • glDrawArrays() slow on iPad?

    - by Nick
    Hey guys, I was wondering how to speed up my iPad application using OpenGLES 2.0. At the moment we have every drawable object draw itself with a call to glDrawArrays(). Blend mode is on, we really need it. Without disabling blendmode, how would we improve performance for this app? For instances, if we now draw 1 texture across the whole screen, the app only gets 15FPS, which is really slow I think? Are we doing something terribly wrong? Our drawing code (for each drawable), is as follows: - (void) draw { GLuint textureAvailable = 0; if(texture != nil){ textureAvailable = 1; } glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture.name); glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, vertices); glEnableVertexAttribArray(ATTRIB_VERTEX); glVertexAttribPointer(ATTRIB_COLOR, 4, GL_FLOAT, 1, 0, colorsWithMultipliedAlpha); glEnableVertexAttribArray(ATTRIB_COLOR); glVertexAttribPointer(ATTRIB_TEXTUREMAP, 2, GL_FLOAT, 1, 0, textureMapping); glEnableVertexAttribArray(ATTRIB_TEXTUREMAP); //Note that we are NOT using position.z here because that is only used to determine drawing order int *jnUniforms = JNOpenGLConstants::getInstance().uniforms; glUniform4f(jnUniforms[UNIFORM_TRANSLATE], position.x, position.y, 0.0, 0.0); glUniform4f(jnUniforms[UNIFORM_SCALE], scale.x, scale.y, 1.0, 1.0); glUniform1f(jnUniforms[UNIFORM_ROTATION], rotation); glUniform1i(jnUniforms[UNIFORM_TEXTURE_SAMPLE], 0); glUniform2f(jnUniforms[UNIFORM_TEXTURE_REPEAT], textureRepeat.x, textureRepeat.y); glUniform1i(jnUniforms[UNIFORM_TEXTURE_AVAILABLE], textureAvailable); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); }

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  • Common causes of slow performing jQuery and how to optimize the code?

    - by Polaris878
    Hello, This might be a bit of a vague or general question, but I figure it might be able to serve as a good resource for other jQuery-ers. I'm interested in common causes of slow running jQuery and how to optimize these cases. We have a good amount of jQuery/JavaScript performing actions on our page... and performance can really suffer with a large number off elements. What are some obvious performance pitfalls you know of with jQuery? What are some general optimizations a jQuery-er can do to squeeze every last bit of performance out of his/her scripts? One example: a developer may use a selector to access an element that is slower than some other way. Thanks

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  • Is "for(;;)" faster than "while (TRUE)"? If not, why do people use it?

    - by Chris Cooper
    for (;;) { //Something to be done repeatedly } I have seen this sort of thing used a lot, but I think it is rather strange... Wouldn't it be much clearer to say while (TRUE), or something along those lines? I'm guessing that (as is the reason for many-a-programmer to resort to cryptic code) this is a tiny margin faster? Why, and is it REALLY worth it? If so, why not just define it this way: #DEFINE while(TRUE) for(;;)

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  • How to optimize this javascript code?

    - by Andrija
    I have a jsp which uses a lot of javascript and it's just not fast enough. I would like to optimize it so first, here's a part of the code: In the jsp I have the initialization: window.onload = function () { formCollection.pageSize.value = "<%= pagingSize%>"; elemCollection = iDom3.Table.all["spis"].XML.DOM; <% if (resultList != null) { %> elementsNumber = <%= resultList.size() %>; <%} else { %> elementsNumber = 0; <% } %> contextPath = "<%= request.getContextPath() %>"; } In my js file I have two types of js functions: // gets the first element and sets it's value to all the other; //the selectSingleNode function is used because I use XSLT transformation //to generate the table _setTehJed = function(){ var resultId = formCollection.elements["idTehJedinice_spis_1"].value; var resultText = formCollection.elements["tehnicka_spis_1"].value; if (resultId != ""){ var counter = 1; while (counter<elementsNumber){ counter++; if(formCollection.elements["idTehJedinice_spis_"+counter] != null){ formCollection.elements["idTehJedinice_spis_"+counter].value=resultId; formCollection.elements["tehnicka_spis_"+counter].value=resultText; } var node=elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'tehnicka']/title"); node.text=resultText; var node2=elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'idTehJedinice']/title"); node2.text=resultId; } } } // sets the elements checkbox to checked or unchecked _SelectCheckRokCuvanja = { all : [], Item : function (oItem, sId) { this.all["spis_"+sId] = oItem.value; if (oItem.checked) { elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "true"); }else{ elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "false"); } } } I've used these tips: http://blogs.msdn.com/b/ie/archive/2006/08/28/728654.aspx http://code.google.com/speed/articles/optimizing-javascript.html but I still think something could be done like defining the functions like this: In the jsp: window.onload = function () { iDom3.DigitalnaArhivaPrihvat.formCollection=document.forms["controller"]; iDom3.DigitalnaArhivaPrihvat.formCollection.pageSize.value = "<%= pagingSize%>"; iDom3.DigitalnaArhivaPrihvat.elemCollection = iDom3.Table.all["spis"].XML.DOM; <% if (resultList != null) { %> iDom3.DigitalnaArhivaPrihvat.elementsNumber = <%= resultList.size() %> <%} else { %> iDom3.DigitalnaArhivaPrihvat.elementsNumber = 0; <% } %> } in the js: iDom3.DigitalnaArhivaPrihvat = { formCollection:null, elemCollection:null, elementsNumber:null, _setTehJed : function(){ var resultId = this.formCollection.elements.idTehJedinice_spis_1.value; var resultText = this.formCollection.elements.tehnicka_spis_1.value; if (resultId != ""){ var counter = 1; while (counter<this.elementsNumber){ counter++; if(this.formCollection.elements["idTehJedinice_spis_"+counter] !== null){ this.formCollection.elements["idTehJedinice_spis_"+counter].value=resultId; this.formCollection.elements["tehnicka_spis_"+counter].value=resultText; } var node=this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'tehnicka']/title"); node.text=resultText; var node2=this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+counter+"']/data[@col = 'idTehJedinice']/title"); node2.text=resultId; } } }, _SelectCheckRokCuvanja = { all : [], Item : function (oItem, sId) { this.all["spis_"+sId] = oItem.value; if (oItem.checked) { this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "true"); }else{ this.elemCollection.selectSingleNode("/suite/table/rows/row[@id = 'spis_"+sId+"']/data[@col = 'rokCheck']").setAttribute("default", "false"); } } } but the problem is scoping (if I do it like this, the second function does not execute properly). Any suggestions?

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  • Ways to optimize Android App code based on function call stack?

    - by K-RAN
    I've been told that Android OS stores all function calls in a stack. This can lead to many problems and cause the 'hiccups' during runtime, even if a program is functionalized properly, correct? So the question is, how can we prevent this from happening? The obvious solution is to functionalize less, along with other sensible acts such as refraining from excessively/needlessly creating objects, performing static calls to functions that don't access fields, etc... Is there another way though? Or can this only be done through careful code writing on the programmers' part? Does the JVM/JIT automatically optimize the bytecode during compile time to account for this?? Thanks a lot for your responses!!

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  • Optimize Binary Search Algorithm

    - by Ganesh M
    In a binary search, we have two comparisons one for greater than and other for less than, otherwise its the mid value. How would you optimize so that we need to check only once? bool binSearch(int array[], int key, int left, int right) { mid = left + (right-left)/2; if (key < array[mid]) return binSearch(array, key, left, mid-1); else if (key > array[mid]) return binSearch(array, key, mid+1, right); else if (key == array[mid]) return TRUE; // Found return FALSE; // Not Found }

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  • Does anybody have any suggestions on which of these two approaches is better for large delete?

    - by RPS
    Approach #1: DECLARE @count int SET @count = 2000 DECLARE @rowcount int SET @rowcount = @count WHILE @rowcount = @count BEGIN DELETE TOP (@count) FROM ProductOrderInfo WHERE ProductId = @product_id AND bCopied = 1 AND FileNameCRC = @localNameCrc SELECT @rowcount = @@ROWCOUNT WAITFOR DELAY '000:00:00.400' Approach #2: DECLARE @count int SET @count = 2000 DECLARE @rowcount int SET @rowcount = @count WHILE @rowcount = @count BEGIN DELETE FROM ProductOrderInfo WHERE ProductId = @product_id AND FileNameCRC IN ( SELECT TOP(@count) FileNameCRC FROM ProductOrderInfo WITH (NOLOCK) WHERE bCopied = 1 AND FileNameCRC = @localNameCrc ) SELECT @rowcount = @@ROWCOUNT WAITFOR DELAY '000:00:00.400' END

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  • optimized grid for rectangular items

    - by peterchen
    I have N rectangular items with an aspect ratio Aitem (X:Y). I have a rectangular display area with an aspect ratio Aview The items should be arranged in a table-like layout (i.e. r rows, c columns). what is the ideal grid rows x columns, so that individual items are largest? (rows * colums = N, of course - i.e. there may be "unused" grid places). A simple algorithm could iterate over rows = 1..N, calculate the required number of columns, and keep the row/column pair with the largest items. I wonder if there's a non-iterative algorithm, though (e.g. for Aitem = Aview = 1, rows / cols can be approximated by sqrt(N)).

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  • negative values in integer programming model

    - by Lucia
    I'm new at using the glpk tool, and after writing a model for certain integer problem and running the solver (glpsol) i get negative values in some constraint that shouldn't be negative at all: No.Row name Activity Lower bound Upper bound 8 act[1] 0 -0 9 act[2] -3 -0 10 act[2] -2 -0 That constraint is defined like this: act{j in J}: sum{i in I} d[i,j] <= y[j]*m; where the sets and variables used are like this: param m, integer, 0; param n, integer, 0; set I := 1..m; set J := 1..n; var y{j in J}, binary; As the upper bound is negative, i think the problem may be in the y[j]*m parte, of the right side of the inequality.. perhaps something with the multiplication of binarys? or that the j in that side of the constrait is undefined? i dont know... i would be greatly grateful if someone can help me with this! :) and excuse for my bad english thanks in advance!

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • In SQL Server what is most efficient way to compare records to other records for duplicates with in

    - by Glenn
    We have an SQL Server that gets daily imports of data files from clients. This data is interrelated and we are always scrubbing it and having to look for suspect duplicate records between these files. Finding and tagging suspect records can get pretty complicated. We use logic that requires some field values to be the same, allows some field values to differ, and allows a range to be specified for how different certain field values can be. The only way we've found to do it is by using a cursor based process, and it places a heavy burden on the database. So I wanted to ask if there's a more efficient way to do this. I've heard it said that there's almost always a more efficient way to replace cursors with clever JOINS. But I have to admit I'm having a lot of trouble with this one. For a concrete example suppose we have 1 table, an "orders" table, with the following 6 fields. order_id, customer_id product_id, quantity, sale_date, price We want to look through the records to find suspect duplicates on the following example criteria. These get increasingly harder. 1. Records that have the same product_id, sale_date, and quantity but different customer_id's should be marked as suspect duplicates for review. 2. Records that have the same customer_id, product_id, quantity and have sale_dates within five days of each other should be marked as suspect duplicates for review 3. Records that have the same customer_id, product_id, but different quantities within 20 units, and sales dates within five days of each other should be considered suspect. Is it possible to satisfy each one of these criteria with a single SQL Query that uses JOINS? Is this the most efficient way to do this?

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  • 50 million+ Rows of Data - CSV or MySQL

    - by eWizardII
    Hello, I have a CSV file which is about 1GB big and contains about 50million rows of data, I am wondering is it better to keep it as a CSV file or store it as some form of a database. I don't know a great deal about MySQL to argue for why I should use it or another database framework over just keeping it as a CSV file. I am basically doing a Breadth-First Search with this dataset, so once I get the initial "seed" set the 50million I use this as the first values in my queue. Thanks,

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  • PHP Increasing writing to page speed.

    - by Frederico
    I'm currently writing out xml and have done the following: header ("content-type: text/xml"); header ("content-length: ".strlen($xml)); $xml being the xml to be written out. I'm near about 1.8 megs of text (which I found via firebug), it seems as the writing is taking more time than the script to run.. is there a way to increase this write speed? Thank you in advance.

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  • Allocated Private Bytes keeps going up in one computer but not the other

    - by Jacob
    OK, this may sound weird, but here goes. There are 2 computers, A (Pentium D) and B (Quad Core) with almost the same amount of RAM. If I run the same code on both computers, the allocated private bytes in A never goes down resulting in a crash later on. In B it looks like the private bytes is constantly deallocated and everything looks fine. In both computers, the working set is deallocated and allocated similarly. Could this be an issue with manifests or DLLs (system)? I'm clueless. Note: I observed the utilized memory with Process Explorer.

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