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  • C99 variable length automatic array performance

    - by aaa
    Is there significant cpu/memory overhead associated with using automatic arrays with g++/Intel on 64-bit x86 linux platform? int function(int N) { double array[N]; overhead compared to allocating array before hand (assuming function is called multiple times) overhead compared to using new overhead compared to using malloc The range of N may be from 1kb to 16kb roughly, stack overrun is not a problem.

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  • PropertyUtils performance

    - by mR_fr0g
    I have a problem where i need to walk through an object graph and pick out a particular property value. My original solution caches a linked list of property names that need to be applied in order to get from point A to point B in the object graph. I then use apache commons PropertyUtils to iterate through the linked list calling getProperty(Object bean, String name) until i have reached point B. My question is around how this will perform compared to perhaps cahing the Method objects for each step. What is propertyUtils doing under the bonnet? Is it doing a lot of reflection / heavy lifting?

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  • Objective C iPhone performance issue

    - by Asad Khan
    Ok guys I am developing an iPhone app I have a Model class which follows a Singleton design pattern. Now I have an NSArray in it which is initialized to around some 1000 NSStrings in the init method. Now I need to use this data in some view controller. so I import Model.h, I create an array of NSString objects in view controller & set the data to it. But now the problem is that now I have 2000 NSStrings currently allocated, which I believe is not a good thing on iPhone due to memory considerations. releasing model object wont help because I've overrided release method to release nothing according to the pattern & I cannot change the design now because now a lot of code works on the assumption of model being a singleton. & in future maybe the initial NSStrings may grow to 2000 or even more & then I'll have 4000 NSStrings allocated at one time .... I am a little confused on how to go about it any suggestions

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  • Strange performance behaviour

    - by plastilino
    I'm puzzled with this. In my machine Direct calculation: 375 ms Method calculation: 3594 ms, about TEN times SLOWER If I place the method calulation BEFORE the direct calculation, both times are SIMILAR. Woud you check it in your machine? class Test { static long COUNT = 50000 * 10000; private static long BEFORE; /*--------METHOD---------*/ public static final double hypotenuse(double a, double b) { return Math.sqrt(a * a + b * b); } /*--------TIMER---------*/ public static void getTime(String text) { if (BEFORE == 0) { BEFORE = System.currentTimeMillis(); return; } long now = System.currentTimeMillis(); long elapsed = (now - BEFORE); BEFORE = System.currentTimeMillis(); if (text.equals("")) { return; } String message = "\r\n" + text + "\r\n" + "Elapsed time: " + elapsed + " ms"; System.out.println(message); } public static void main(String[] args) { double a = 0.2223221101; double b = 122333.167; getTime(""); /*--------DIRECT CALCULATION---------*/ for (int i = 1; i < COUNT; i++) { Math.sqrt(a * a + b * b); } getTime("Direct: "); /*--------METHOD---------*/ for (int k = 1; k < COUNT; k++) { hypotenuse(a, b); } getTime("Method: "); } }

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  • C++ Performance/memory optimization guidelines

    - by ML
    Hi All, Does anyone have a resource for C++ memory optimization guidelines? Best practices, tuning, etc? As an example: Class xxx { public: xxx(); virtual ~xxx(); protected: private: }; Would there be ANY benefit on the compiler or memory allocation to get rid of protected and private since there there are no items that are protected and private in this class?

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  • HTML 5 performance on Firefox ?

    - by asksuperuser
    I tried this sample here: http://9elements.com/io/projects/html5/canvas/ After a few minutes, Firefox slows down so much I can't even popup any menu. When I closed the tab, Firefox comes back to normal again. So is HTML 5 really a good choice now ?

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  • C++ application as a service with high performance

    - by sand
    I need to provide a C++ application as a service. Client of the service and the service can be on the same machine or distributed on different machines based on the load. This application takes a ~2KB string as input and returns almost similar size of string after some processing. Turnaround time for the client should be really quick. What is the best mechanism to implement this?

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  • Sharepoint Web performance optimization

    - by hertzel
    We are running on SSL on following server topology: 1 ISA (SSL Terminate/cache/proxy+AD authentication) 1 Sharepoint 1 IBM DB2 Database as enterprise/corporate DB 1 MS SQL Server as local DB We have recently optimized the caching, compression, minification, and other ASP.net best practices such as viewstate and cookie sizes, minimizing round trips, parallel connections/domain sharding and a lot more.... Now we are not convinced that the we are in an optimized position as the network resources i.e. bandwidth and especially latency are out of our control!! The client/browser to server/sharepoint is trans-Atlantic i.e. (ASIA, USA, EUROPE). As of my understanding the only ways to improve the network (latency) are: - TCP/SSL optimization - hardware/software? - CDNs - cloud or our own ? Your opinion and insights would be much appreciated Best regards Hertzel

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  • Improve disk read performance (multiple files) with threading

    - by pablo
    I need to find a method to read a big number of small files (about 300k files) as fast as possible. Reading them sequentially using FileStream and reading the entire file in a single call takes between 170 and 208 seconds (you know, you re-run, disk cache plays its role and time varies). Then I tried using PInvoke with CreateFile/ReadFile and using FILE_FLAG_SEQUENTIAL_SCAN, but I didn't appreciate any changes. I tried with several threads (divide the big set in chunks and have every thread reading its part) and this way I was able to improve speed just a little bit (not even a 5% with every new thread up to 4). Any ideas on how to find the most effective way to do this?

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  • Performance of Serialized Objects in C++

    - by jm1234567890
    Hi Everyone, I'm wondering if there is a fast way to dump an STL set to disk and then read it back later. The internal structure of a set is a binary tree, so if I serialize it naively, when I read it back the program will have to go though the process of inserting each element again. I think this is slow even if it is read back in correct order, correct me if I am wrong. Is there a way to "dump" the memory containing the set into disk and then read it back later? That is, keep everything in binary format, thus avoiding the re-insertion. Do the boost serialization tools do this? Thanks! EDIT: oh I should probably read, http://www.parashift.com/c++-faq-lite/serialization.html I will read it now... no it doesn't really help

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  • C# Performance on Errors

    - by pm_2
    It would appear that catching an error is slower that performing a check prior to the error (for example a TryParse). The related questions that prompt this observation are here and here. Can anyone tell me why this is so - why is it more costly to catch an error that to perform one or many checks of the data to prevent the error?

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  • postgres min function performance

    - by wutzebaer
    hi i need the lowest value for runnerId this query: SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ; takes 80ms (1968 result rows) this SELECT min("runnerId") FROM betlog WHERE "marketId" = '107416794' ; takes 1600ms is there a faster way to find the minimum, or should i calc the min in my java programm? "Result (cost=100.88..100.89 rows=1 width=0)" " InitPlan 1 (returns $0)" " -> Limit (cost=0.00..100.88 rows=1 width=9)" " -> Index Scan using runneridindex on betlog (cost=0.00..410066.33 rows=4065 width=9)" " Index Cond: ("runnerId" IS NOT NULL)" " Filter: ("marketId" = 107416794::bigint)" CREATE INDEX marketidindex ON betlog USING btree ("marketId" COLLATE pg_catalog."default"); another idea SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ORDER BY "runnerId" LIMIT 1 >1600ms SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ORDER BY "runnerId" >>100ms how can a limit slow the query down?

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  • Objective-C vs JavaScript loop performance

    - by micadelli
    I have a PhoneGap mobile application that I need to generate an array of match combinations. In JavaScript side, the code hanged pretty soon when the array of which the combinations are generated from got a bit bigger. So, I thought I'll make a plugin to generate the combinations, passing the array of javascript objects to native side and loop it there. To my surprise the following codes executes in 150 ms (JavaScript) whereas in native side (Objective-C) it takes ~1000 ms. Does anyone know any tips for speeding up those executing times? When players exceeds 10, i.e. the length of the array of teams equals 252 it really gets slow. Those execution times mentioned above are for 10 players / 252 teams. Here's the JavaScript code: for (i = 0; i < GAME.teams.length; i += 1) { for (j = i + 1; j < GAME.teams.length; j += 1) { t1 = GAME.teams[i]; t2 = GAME.teams[j]; if ((t1.mask & t2.mask) === 0) { GAME.matches.push({ Team1: t1, Team2: t2 }); } } } ... and here's the native code: NSArray *teams = [[NSArray alloc] initWithArray: [options objectForKey:@"teams"]]; NSMutableArray *t = [[NSMutableArray alloc] init]; int mask_t1; int mask_t2; for (NSInteger i = 0; i < [teams count]; i++) { for (NSInteger j = i + 1; j < [teams count]; j++) { mask_t1 = [[[teams objectAtIndex:i] objectForKey:@"mask"] intValue]; mask_t2 = [[[teams objectAtIndex:j] objectForKey:@"mask"] intValue]; if ((mask_t1 & mask_t2) == 0) { [t insertObject:[teams objectAtIndex:i] atIndex:0]; [t insertObject:[teams objectAtIndex:j] atIndex:1]; /* NSArray *newCombination = [[NSArray alloc] initWithObjects: [teams objectAtIndex:i], [teams objectAtIndex:j], nil]; */ [combinations addObject:t]; } } } ... the array in question (GAME.teams) looks like this: { count = 2; full = 1; list = ( { index = 0; mask = 1; name = A; score = 0; }, { index = 1; mask = 2; name = B; score = 0; } ); mask = 3; name = A; }, { count = 2; full = 1; list = ( { index = 0; mask = 1; name = A; score = 0; }, { index = 2; mask = 4; name = C; score = 0; } ); mask = 5; name = A; },

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  • Python performance profiling (file close)

    - by user1853986
    First of all thanks for your attention. My question is how to reduce the execution time of my code. Here is the relevant code. The below code is called in iteration from the main. def call_prism(prism_input_file,random_length): prism_output_file = "path.txt" cmd = "prism %s -simpath %d %s" % (prism_input_file,random_length,prism_output_file) p = os.popen(cmd) p.close() return prism_output_file def main(prism_input_file, number_of_strings): ... for n in range(number_of_strings): prism_output_file = call_prism(prism_input_file,z[n]) ... return I used statistics from the "profile statistics browser" when I profiled my code. The "file close" system command took the maximum time (14.546 seconds). The call_prism routine is called 10 times. But the number_of_strings is usually in thousands, so, my program takes lot of time to complete. Let me know if you need more information. By the way I tried with subprocess, too. Thanks.

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  • How can I improve the performance of this algorithm

    - by Justin
    // Checks whether the array contains two elements whose sum is s. // Input: A list of numbers and an integer s // Output: return True if the answer is yes, else return False public static boolean calvalue (int[] numbers, int s){ for (int i=0; i< numbers.length; i++){ for (int j=i+1; j<numbers.length;j++){ if (numbers[i] < s){ if (numbers[i]+numbers[j] == s){ return true; } } } } return false; }

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  • PHP array performance

    - by dfo
    Hi, this is my first question on Stackoverflow, please bear with me. I'm testing an algorithm for 2d bin packing and I've chosen PHP to mock it up as it's my bread-and-butter language nowadays. As you can see on http://themworks.com/pack_v0.2/oopack.php?ol=1 it works pretty well, but you need to wait around 10-20 seconds for 100 rectangles to pack. For some hard to handle sets it would hit the php's 30s runtime limit. I did some profiling and it shows that most of the time my script goes through different parts of a small 2d array with 0's and 1's in it. It either checks if certain cell equals to 0/1 or sets it to 0/1. It can do such operations million times and each times it takes few microseconds. I guess I could use an array of booleans in a statically typed language and things would be faster. Or even make an array of 1 bit values. I'm thinking of converting the whole thing to some compiled language. Is PHP just not good for it? If I do need to convert it to let's say C++, how good are the automatic converters? My script is just a lot of for loops with basic arrays and objects manipulations. Thank you! Edit. This function gets called more than any other. It reads few properties of a very simple object, and goes through a very small part of a smallish array to check if there's any element not equal to 0. function fits($bin, $file, $x, $y) { $flag = true; $xw = $x + $file->get_width();; $yh = $y + $file->get_height(); for ($i = $x; $i < $xw; $i++) { for ($j = $y; $j < $yh; $j++) { if ($bin[$i][$j] !== 0) { $flag = false; break; } } if (!$flag) break; } return $flag; }

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  • C/C++ variable length automatic array performance

    - by aaa
    hello. Is there significant cpu/memory overhead associated with using automatic arrays with g++/Intel on 64-bit x86 linux platform? int function(int N) { double array[N]; overhead compared to allocating array before hand (assuming function is called multiple times) overhead compared to using new overhead compared to using malloc range of N maybe from 1kb to 16kb roughly, stack overrun is not a problem Thank you

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  • Which should I use? (performance)

    - by Yim
    I want to know a simple thing: when setting up a style that is inherited by all its children, is it recommended most specific? (even if you don't care others having this style) Structure: html body parent_content wrapper p I don't care having parent_content or wrapper having the style I do care changing the html or body style (or all p) So what should I use? #parent_content{ color:#555; } #parent_content p{ color:#555; } #wrapper{ color:#555; } ... Also, some links to tutorials about this would be great

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  • Will logging debugging incur a performance hit if I don't turn debugging on?

    - by romandas
    On a Cisco device, I know that enabling debugging can incur a performance hit since debugging has such a high priority on the CPU. I know that to log debugging, you have to set logging up to the debugging level (logging buffered 4096 debugging, for example) and also enable debugging on some feature. Does configuring the logging debugging incur the performance hit even if you don't enable debugging on some feature, or would it be safe (assuming you want and can handle all the logging events via syslog) to configure 'logging buffered 4096 debugging' to have maximum logging available if/when someone uses debug?

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