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• Browser timing out attempting to load images

  - by notJim

  I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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• Will creating index help in this case

  - by The King

  I'm still a learning user of SQL-SERVER2005. Here is my table structure CREATE TABLE [dbo].[Trn_PostingGroups]( [ControlGroup] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [PracticeCode] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [ScanDate] [smalldatetime] NULL, [DepositDate] [smalldatetime] NULL, [NameOfFile] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, [DepositValue] [decimal](11, 2) NULL, [RecordStatus] [char](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, CONSTRAINT [PK_Trn_PostingGroups_1] PRIMARY KEY CLUSTERED ( [ControlGroup] ASC, [PracticeCode] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] Scenario 1 : Suppose I have a query like this... Select * from Trn_PostingGroups where PracticeCode = 'ABC' Will indexing on Practice Code seperately help me in making my query faster?? Scenario 2 : Select * from Trn_PostingGroups where ControlGroup = 12701 and PracticeCode = 'ABC' and NameOfFile = 'FileName1' Will indexing on NameOfFile seperately help me in making my query faster ??

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• What would be a better way of doing the following

  - by thecoshman

  if(get_magic_quotes_gpc()) { $location_name = trim(mysql_real_escape_string(trim(stripslashes($_GET['location_name'])))); } else { $location_name = trim(mysql_real_escape_string(trim($_GET['location_name']))); } That's the code I have so far. seems to me this code is fundamentally ... OK. Do you think I can safely remove the inner trim(). Please try not a spam me with endless version of this, I want to try to learn how to do this better.

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• Any reason not to use USE_ETAGS with CommonMiddleware in Django?

  - by allyourcode

  The only reason I can think of is that calculating ETag's might be expensive. If pages change very quickly, the browser's cache is likely to be invalidated by the ETag. In that case, calculating the ETag would be a waste of time. On the other hand, a giving a 304 response when possible minimizes the amount of time spent in transmission. What are some good guidelines for when ETag's are likely to be a net winner when implemented with Django's CommonMiddleware?

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• Tools for Window service performacne test

  - by user171523

  I would like to know what are the open source and commerical tools for window Service Testing. Like memeory usage and code leakes etc .. C# 2.0 - Window Service.

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• Does having a longer string in a SQL Like expression allow hinder or help query executing speed?

  - by Allain Lalonde

  I have a db query that'll cause a full table scan using a like clause and came upon a question I was curious about... Which of the following should run faster in Mysql or would they both run at the same speed? Benchmarking might answer it in my case, but I'd like to know the why of the answer. The column being filtered contains a couple thousand characters if that's important. SELECT * FROM users WHERE data LIKE '%=12345%' or SELECT * FROM users WHERE data LIKE '%proileId=12345%' I can come up for reasons why each of these might out perform the other, but I'm curious to know the logic.

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• MySQL left outer join is slow

  - by Ryan Doherty

  Hi, hoping to get some help with this query, I've worked at it for a while now and can't get it any faster: SELECT date, count(id) as 'visits' FROM dates LEFT OUTER JOIN visits ON (dates.date = DATE(visits.start) and account_id = 40 ) WHERE date >= '2010-12-13' AND date <= '2011-1-13' GROUP BY date ORDER BY date ASC That query takes about 8 seconds to run. I've added indexes on dates.date, visits.start, visits.account_id and visits.start+visits.account_id and can't get it to run any faster. Table structure (only showing relevant columns in visit table): create table visits ( `id` int(11) NOT NULL AUTO_INCREMENT, `account_id` int(11) NOT NULL, `start` DATETIME NOT NULL, `end` DATETIME NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; CREATE TABLE `dates` ( `date` date NOT NULL, PRIMARY KEY (`date`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; dates table contains all days from 2010-1-1 to 2020-1-1 (~3k rows). visits table contains about 400k rows dating from 2010-6-1 to yesterday. I'm using the date table so the join will return 0 visits for days there were no visits. Results I want for reference: +------------+--------+ | date | visits | +------------+--------+ | 2010-12-13 | 301 | | 2010-12-14 | 356 | | 2010-12-15 | 423 | | 2010-12-16 | 332 | | 2010-12-17 | 346 | | 2010-12-18 | 226 | | 2010-12-19 | 213 | | 2010-12-20 | 311 | | 2010-12-21 | 273 | | 2010-12-22 | 286 | | 2010-12-23 | 241 | | 2010-12-24 | 149 | | 2010-12-25 | 102 | | 2010-12-26 | 174 | | 2010-12-27 | 258 | | 2010-12-28 | 348 | | 2010-12-29 | 392 | | 2010-12-30 | 395 | | 2010-12-31 | 278 | | 2011-01-01 | 241 | | 2011-01-02 | 295 | | 2011-01-03 | 369 | | 2011-01-04 | 438 | | 2011-01-05 | 393 | | 2011-01-06 | 368 | | 2011-01-07 | 435 | | 2011-01-08 | 313 | | 2011-01-09 | 250 | | 2011-01-10 | 345 | | 2011-01-11 | 387 | | 2011-01-12 | 0 | | 2011-01-13 | 0 | +------------+--------+ Thanks in advance for any help!

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• C++, using one byte to store two variables

  - by 2di

  Hi All I am working on representation of the chess board, and I am planning to store it in 32 bytes array, where each byte will be used to store two pieces. (That way only 4 bits are needed per piece) Doing it in that way, results in a overhead for accessing particular index of the board. Do you think that, this code can be optimised or completely different method of accessing indexes can be used? c++ char getPosition(unsigned char* c, int index){ //moving pointer c+=(index>>1); //odd number if (index & 1){ //taking right part return *c & 0xF; }else { //taking left part return *c>>4; } } void setValue(unsigned char* board, char value, int index){ //moving pointer board+=(index>>1); //odd number if (index & 1){ //replace right part //save left value only 4 bits *board = (*board & 0xF0) + value; }else { //replacing left part *board = (*board & 0xF) + (value<<4); } } int main() { char* c = (char*)malloc(32); for (int i = 0; i < 64 ; i++){ setValue((unsigned char*)c, i % 8,i); } for (int i = 0; i < 64 ; i++){ cout<<(int)getPosition((unsigned char*)c, i)<<" "; if (((i+1) % 8 == 0) && (i > 0)){ cout<<endl; } } return 0; } I am equally interested in your opinions regarding chess representations, and optimisation of the method above, as a stand alone problem. Thanks a lot

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• Measuring the CPU frequency scaling effect

  - by Bryan Fok

  Recently I am trying to measure the effect of the cpu scaling. Is it accurate if I use this clock to measure it? template<std::intmax_t clock_freq> struct rdtsc_clock { typedef unsigned long long rep; typedef std::ratio<1, clock_freq> period; typedef std::chrono::duration<rep, period> duration; typedef std::chrono::time_point<rdtsc_clock> time_point; static const bool is_steady = true; static time_point now() noexcept { unsigned lo, hi; asm volatile("rdtsc" : "=a" (lo), "=d" (hi)); return time_point(duration(static_cast<rep>(hi) << 32 | lo)); } }; Update: According to the comment from my another post, I believe redtsc cannot use for measure the effect of cpu frequency scaling because the counter from the redtsc does not affected by the CPU frequency, am i right?

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• Is is faster to filter and get data or filter then get data ?

  - by remi bourgarel

  Hi I have this kind of request : SELECT myTable.ID, myTable.Adress, -- 20 more columns of all kind of type FROM myTable WHERE EXISTS(SELECT * FROM myLink WHERE myLink.FID = myTable.ID and myLink.FID2 = 666) myLink has a lot of rows. Do you think it's faster to do like this : SELECT myLink.FID INTO @result FROM myLink WHERE myLink.FID2 = 666 UPDATE @result SET Adress = myTable.Adress, -- 20 more columns of all kind of type FROM myTable WHERE myTable.ID = @result.ID

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• How to effectively measure difference in a run-time.

  - by Knowing me knowing you

  Guys, in one of the excersises in TC++PL B.S. asks to: "Write a function that either returns a value or that throws that value based on an argument. Measure the difference in run-time between the two ways." Great pity he never explaines how to measure such things. I'm not sure if I'm suppose to write simple "time start, time end" counter or maybe there are more effective and practical ways to do it? Thanks in advance.

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• Slow first page load on asp.net site

  - by Tabloo Quijico

  Hi, Every now and then (always after a long period of idle-time, e.g. overnight) when I access a site built using asp.net - it takes around 15 seconds to load the page (15 seconds before I see any progress whatsoever, then the page comes up fast). Further pages on that site, or refreshes, are quick as usual - they are also fast on other machines, only the first one seems to take the 'hit'. Page tracing never through anything up (whole cycle was a fraction of a second) So my question is where else should I be looking? Perhaps IIS? Or could it still be my asp.net app and I'm just looking in the wrong place (the trace) for clues? As I don't have much control over the IIS server, anything I can check through asp.net would be more helpful, before I go ask that particular admin. cheers :D

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• Time complexity of a powerset generating function

  - by Lirik

  I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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• Optimizing NSNumber numberWithInt:

  - by Riviera

  I am profiling an iPhone app and I noticed a strange pattern. In a certain block of code that's called quite frequently... [item setQuadrant:[NSNumber numberWithInt:a]]; [item setIndex:[NSNumber numberWithInt:b]]; [item setTimestamp:[NSNumber numberWithInt:c]]; [item setState:[NSNumber numberWithInt:d]]; [item setCompletionPercentage:[NSNumber numberWithInt:e]]; [item setId_:[NSNumber numberWithInt:f]]; ...the first call to [NSNumber numberWithInt:] takes an inordinate amount of time, in the order of 10-15x that of the remaining calls. I've verified that the results are consistent if I shuffle the lines (the first line is always the slow one, by the same ratio). Is there something going on that I'm not aware of? Perhaps this happens because this block is inside a try/catch?

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• Counting context switches per thread

  - by Sarmun

  Is there a way to see how many context switches each thread generates? (both in and out if possible) Either in X/s, or to let it run and give aggregated data after some time. (either on linux or on windows) I have found only tools that give aggregated context-switching number for whole os or per process. My program makes many context switches (50k/s), probably a lot not necessary, but I am not sure where to start optimizing, where do most of those happen.

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• Database for Large number of 1kB data chunks (MySQL?)

  - by The Unknown

  I have a very large dataset, each item in the dataset being roughly 1kB in size. The data needs to be queried rapidly by many applications distributed over a network. The dataset has more than a million items (so 500 million+ 1kB data chunks). What would be the best method to storing this dataset (need to allow adding more items, and reading them rapidly, but never modifying already added data)? Would using a MySQL DB using the binary blob format be appropriate? Or should each of these be stored as files on a file system? edit: the number is 1 million items now, but needs to be able to scale to well over 500 million items easily.

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• ASP.NET problem - Firebug shows odd behaviour

  - by Brandi

  I have an ASP.NET application that does a large database read. It loads up a gridview inside an update panel. In VS2008, just running on my local machine, it runs fantastically. In production (identical code, just published and put on one of our network servers), it runs slow as dirt. Debug is set to false, so this is not the cause of the slow down. I'm not an experienced web developer, so besides that, feel free to suggest the obvious. I have been using Firebug to determine what's going on, and here is what that has turned up: On production, there are around 500 requests. The timeline bar is very short. The size column varies from run to run, but is always the same for the duration of the run. Locally, there are about 30 requests. The timeline bar takes up the entire space. Can anyone shed some light on why this is happening and what I can do to fix it? Also, I can't find much of anything on the web about this, so any references are helpful too.

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• How to speed this kind of for-loop?

  - by wok

  I would like to compute the maximum of translated images along the direction of a given axis. I know about ordfilt2, however I would like to avoid using the Image Processing Toolbox. So here is the code I have so far: imInput = imread('tire.tif'); n = 10; imMax = imInput(:, n:end); for i = 1:(n-1) imMax = max(imMax, imInput(:, i:end-(n-i))); end Is it possible to avoid using a for-loop in order to speed the computation up, and, if so, how?

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• VBScript - using IF statements in a mail script?

  - by Kenny Bones

  I really need some quick tips here. I've got this VBScript script which sends an e-mail. And I want to do several checks to see if an attribute is true and if it is, write an additional line in the mail. How can I do this? This is part of the script: obMessage.HTMLBody = ""_ & "<MENU>"_ & "<LI type = square>This is a line</i>."_ I want something which looks like this: obMessage.HTMLBody = ""_ & "<MENU>"_ If statement1 = true Then & "<LI type = square>This is an additional line</i>."_ end if Preferrably, could some select statements be made? I don't really mind what the code looks like, I just want it to work as soon as possible :)

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• Objective-C and Protocols

  - by SpecialK

  Do protocols come with any overhead? (ie. obvious benefits aside, do they slow things down?)

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• Quickest way to compare a buch of array or list of values.

  - by zapping

  Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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• What are the suggested alternatives for Class<T>.isAssignableFrom(Class<?> cls)?

  - by Wing C. Chen

  Currently I am doing the profiling to a piece of code. During the profiling, I discovered that this very method call, Class<T>.isAssignableFrom(Class<?> cls) takes up to quite amount of the entire time. Because this is a method from reflection, it takes a lot of time compared to normal keywords or method calls. I am wondering if there are some good alternatives for this method calls?

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• Using code from this site

  - by user553798

  Hi, The legal section of this site mentions that all code by the contributors is licensed under the Creative Commons Attribution Share Alike License. Does this mean that I have to attribute the submitter even if the code in question is a few lines amongst hundreds or thousands of lines of code? What if I use code from a book or SDK? For eg; If I use the sample code from Google's Android SDK documentation, does that mean I need to attribute Google every time I write an app, after all it would be impossible to write an app without consulting the SDK docs, atleast initially... I am totally confused :S

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• Long primitive or AtomicLong for a counter?

  - by Rich

  Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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• Having to insert a record, then update the same record warrants 1:1 relationship design?

  - by dianovich

  Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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