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• Optimizing landing pages

  - by Oleg Shaldybin

  In my current project (Rails 2.3) we have a collection of 1.2 million keywords, and each of them is associated with a landing page, which is effectively a search results page for a given keywords. Each of those pages is pretty complicated, so it can take a long time to generate (up to 2 seconds with a moderate load, even longer during traffic spikes, with current hardware). The problem is that 99.9% of visits to those pages are new visits (via search engines), so it doesn't help a lot to cache it on the first visit: it will still be slow for that visit, and the next visit could be in several weeks. I'd really like to make those pages faster, but I don't have too many ideas on how to do it. A couple of things that come to mind: build a cache for all keywords beforehand (with a very long TTL, a month or so). However, building and maintaing this cache can be a real pain, and the search results on the page might be outdated, or even no longer accessible; given the volatile nature of this data, don't try to cache anything at all, and just try to scale out to keep up with traffic. I'd really appreciate any feedback on this problem.

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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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• C++ Function pointers vs Switch

  - by Perfix

  What is faster: Function pointers or switch? The switch statement would have around 30 cases, consisting of enumarated unsigned ints from 0 to 30. I could do the following: class myType { FunctionEnum func; string argv[123]; int someOtherValue; }; // In another file: myType current; // Iterate through a vector containing lots of myTypes // ... for ( i=0; i < myVecSize; i ++ ) switch ( current.func ) { case 1: //... break; // ........ case 30: // blah break; } And go trough the switch with func every time. The good thing about switch would also be that my code is more organized than with 30 functions. Or I could do that (not so sure with that): class myType { myReturnType (*func); string argv[123]; int someOtherValue; }; I'd have 30 different functions then, at the beginning a pointer to one of them is assigned to myType. What is probably faster: Switch statement or function pointer? Calls per second: Around 10 million. I can't just test it out - that would require me to rewrite the whole thing. Currently using switch. I'm building an interpreter which I want to be faster than Python & Ruby - every clock cycle matters!

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• how do i do very fast inserts to SQL Server 2008

  - by CharlesO

  I have a project that involves recording data from a device directly into a sql table. I do very little processing in code before writing to sql server (2008 express by the way) typically i use the sqlhelper class's ExecuteNoneQuery method and pass in a stored proc name and list of parameters that the SP expects. This is very convenient, but i need a much faster way of doing this. Thanks.

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• JavaScript: Is there a better way to retain your array but efficiently concat or replace items?

  - by Michael Mikowski

  I am looking for the best way to replace or add to elements of an array without deleting the original reference. Here is the set up: var a = [], b = [], c, i, obj; for ( i = 0; i < 100000; i++ ) { a[ i ] = i; b[ i ] = 10000 - i; } obj.data_list = a; Now we want to concatenate b INTO a without changing the reference to a, since it is used in obj.data_list. Here is one method: for ( i = 0; i < b.length; i++ ) { a.push( b[ i ] ); } This seems to be a somewhat terser and 8x (on V8) faster method: a.splice.apply( a, [ a.length, 0 ].concat( b ) ); I have found this useful when iterating over an "in-place" array and don't want to touch the elements as I go (a good practice). I start a new array (let's call it keep_list) with the initial arguments and then add the elements I wish to retain. Finally I use this apply method to quickly replace the truncated array: var keep_list = [ 0, 0 ]; for ( i = 0; i < a.length; i++ ){ if ( some_condition ){ keep_list.push( a[ i ] ); } // truncate array a.length = 0; // And replace contents a.splice.apply( a, keep_list ); There are a few problems with this solution: there is a max call stack size limit of around 50k on V8 I have not tested on other JS engines yet. This solution is a bit cryptic Has anyone found a better way?

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• Create a PHP cache system in MySQL database?

  - by Zach Smith

  I'm creating a web service that often scrapes data from remote web pages. After scraping this data, I have a simple multidimensional array of information to use. The scraping process is fairly taxing on my server, and the page load takes a while. I was considering adding a simple cache system using a MySQL database, where I create one row per remote web page with a the array of information pulled from it stored as a JSON encoded string. Is this a good enough system? Or would something like a text file per web page be a better idea?

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• Which of these choices is the better design for drawing objects?

  - by Adir

  What would be a better parctice, writing the drawing method inside the GameObject class or in the Game class? GameObject obj = new GameObject(); obj.Draw(); Or GameObject obj = new GameObject(); DrawGameObject(obj);

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• can a program written in C be faster than one written in OCaml and translated to C?

  - by Ole Jak

  So I have some cool Image Processing algorithm. I have written it in OCaml. It performs well. I now I can compile it as C code with such command ocamlc -output-obj -o foo.c foo.ml (I have a situation where I am not alowed to use OCaml compiler to bild my programm for my arcetecture, I can use only specialy modified gcc. so I will compile that programm with sometyhing like gcc -L/usr/lib/ocaml foo.c -lcamlrun -lm -lncurses and Itll run on my archetecture.) I want to know in general case can a program written in C be faster than one written in OCaml and translated to C?

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• VS2008 is very slow on a specific large C++ solution

  - by VioletRose

  I have a solution with 21 C++ projects and 1 VB.NET project. The IDE responds very slowly when I simply move the carret in a file or try to open the menu. The process seems to take 50% of CPU for each movement. It only happens with this solution and only on my machine. The solution has total of 2380 source and header files, of which 1280 are header files. I tried to remove all connection to the source control (Perforce) but it didn't help. Also, I have Visual Assist installed but even after removing it (uninstall), the same behavior continued. Any idea?

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• Hibernate Relationship Mapping/Speed up batch inserts

  - by manyxcxi

  I have 5 MySQL InnoDB tables: Test,InputInvoice,InputLine,OutputInvoice,OutputLine and each is mapped and functioning in Hibernate. I have played with using StatelessSession/Session, and JDBC batch size. I have removed any generator classes to let MySQL handle the id generation- but it is still performing quite slow. Each of those tables is represented in a java class, and mapped in hibernate accordingly. Currently when it comes time to write the data out, I loop through the objects and do a session.save(Object) or session.insert(Object) if I'm using StatelessSession. I also do a flush and clear (when using Session) when my line count reaches the max jdbc batch size (50). Would it be faster if I had these in a 'parent' class that held the objects and did a session.save(master) instead of each one? If I had them in a master/container class, how would I map that in hibernate to reflect the relationship? The container class wouldn't actually be a table of it's own, but a relationship all based on two indexes run_id (int) and line (int). Another direction would be: How do I get Hibernate to do a multi-row insert?

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• Sql Server 2000 Stored Procedure Prevents Parallelism or something?

  - by user187305

  I have a huge disgusting stored procedure that wasn't slow a couple months ago, but now is. I barely know what this thing does and I am in no way interested in rewriting it. I do know that if I take the body of the stored procedure and then declare/set the values of the parameters and run it in query analyzer that it runs more than 20x faster. From the internet, I've read that this is probably due to a bad cached query plan. So, I've tried running the sp with "WITH RECOMPILE" after the EXEC and I've also tried putting the "WITH RECOMPLE" inside the sp, but neither of those helped even a little bit. When I look at the execution plan of the sp vs the query, the biggest difference is that the sp has "Parallelism" operations all over the place and the query doesn't have any. Can this be the cause of the difference in speeds? Thank you, any ideas would be great... I'm stuck.

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• Application Role and access second database

  - by lszk

  I have written a script to create an audit trails to my database in a second one db. So far I had no problems during tests on my dev machine from SQL Server Management Studio. Problems started to occurs when I first tried to test my triggers from my application by modyfing data in it. Using profiler I found out, that my audit trails db is not visible in sys.databases, so here lies the problem. The application using an Application Role, so as I found on MSDN, that's why I can't get access to other db on the server. I'm not a DBA. I have no experience with properly settings the security stuff, so please guide me, how can I set the setting for guest account (according to MSDN) to get access to this db? I need to have a record for this database in sys.databases and I need to be able to insert data in this database in all tables. No select, update or delete I need.

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• Intersection() and Except() is too slow with large collections of custom objects

  - by Theo

  I am importing data from another database. My process is importing data from a remote DB into a List<DataModel> named remoteData and also importing data from the local DB into a List<DataModel> named localData. I am then using LINQ to create a list of records that are different so that I can update the local DB to match the data pulled from remote DB. Like this: var outdatedData = this.localData.Intersect(this.remoteData, new OutdatedDataComparer()).ToList(); I am then using LINQ to create a list of records that no longer exist in remoteData, but do exist in localData, so that I delete them from local database. Like this: var oldData = this.localData.Except(this.remoteData, new MatchingDataComparer()).ToList(); I am then using LINQ to do the opposite of the above to add the new data to the local database. Like this: var newData = this.remoteData.Except(this.localData, new MatchingDataComparer()).ToList(); Each collection imports about 70k records, and each of the 3 LINQ operation take between 5 - 10 minutes to complete. How can I make this faster? Here is the object the collections are using: internal class DataModel { public string Key1{ get; set; } public string Key2{ get; set; } public string Value1{ get; set; } public string Value2{ get; set; } public byte? Value3{ get; set; } } The comparer used to check for outdated records: class OutdatedDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { var e = string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2) && ( !string.Equals(x.Value1, y.Value1) || !string.Equals(x.Value2, y.Value2) || x.Value3 != y.Value3 ); return e; } public int GetHashCode(DataModel obj) { return 0; } } The comparer used to find old and new records: internal class MatchingDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { return string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2); } public int GetHashCode(DataModel obj) { return 0; } }

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• Integrate existing Spring based web application with a CMS

  - by anne_developer

  We have stable spring based (spring 2.x) web application. We have a new requirement which is our data entry operators should be able to login to some kind of an admin module and simply change the text in the web pages, change the color etc. I have seen PHP based CMS’s that allows authorized user to change the content in WYSIWYG manner. If anyone of you knows such open source Java CMS or third party application, which can facilitate such thing, please let me know. Please note: we cannot write our application from scratch. We are looking for pluggable component.

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• Slowing process creation under Java?

  - by oconnor0

  I have a single, large heap (up to 240GB, though in the 20-40GB range for most of this phase of execution) JVM [1] running under Linux [2] on a server with 24 cores. We have tens of thousands of objects that have to be processed by an external executable & then load the data created by those executables back into the JVM. Each executable produces about half a megabyte of data (on disk) that when read right in, after the process finishes, is, of course, larger. Our first implementation was to have each executable handle only a single object. This involved the spawning of twice as many executables as we had objects (since we called a shell script that called the executable). Our CPU utilization would start off high, but not necessarily 100%, and slowly worsen. As we began measuring to see what was happening we noticed that the process creation time [3] continually slows. While starting at sub-second times it would eventually grow to take a minute or more. The actual processing done by the executable usually takes less than 10 seconds. Next we changed the executable to take a list of objects to process in an attempt to reduce the number of processes created. With batch sizes of a few hundred (~1% of our current sample size), the process creation times start out around 2 seconds & grow to around 5-6 seconds. Basically, why is it taking so long to create these processes as execution continues? [1] Oracle JDK 1.6.0_22 [2] Red Hat Enterprise Linux Advanced Platform 5.3, Linux kernel 2.6.18-194.26.1.el5 #1 SMP [3] Creation of the ProcessBuilder object, redirecting the error stream, and starting it.

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• Running Boggle Solver takes over an hour to run. What is wrong with my code?

  - by user1872912

  So I am running a Boggle Solver in java on the NetBeans IDE. When I run it, i have to quit after 10 minutes or so because it will end up taking about 2 hour to run completely. Is there something wrong with my code or a way that will make is substantially faster? public void findWords(String word, int iLoc, int jLoc, ArrayList<JLabel> labelsUsed){ if(iLoc < 0 || iLoc >= 4 || jLoc < 0 || jLoc >= 4){ return; } if(labelsUsed.contains(jLabels[iLoc][jLoc])){ return; } word += jLabels[iLoc][jLoc].getText(); labelsUsed.add(jLabels[iLoc][jLoc]); if(word.length() >= 3 && wordsPossible.contains(word)){ wordsMade.add(word); } findWords(word, iLoc-1, jLoc, labelsUsed); findWords(word, iLoc+1, jLoc, labelsUsed); findWords(word, iLoc, jLoc-1, labelsUsed); findWords(word, iLoc, jLoc+1, labelsUsed); findWords(word, iLoc-1, jLoc+1, labelsUsed); findWords(word, iLoc-1, jLoc-1, labelsUsed); findWords(word, iLoc+1, jLoc-1, labelsUsed); findWords(word, iLoc+1, jLoc+1, labelsUsed); labelsUsed.remove(jLabels[iLoc][jLoc]); } here is where I call this method from: public void findWords(){ ArrayList <JLabel> labelsUsed = new ArrayList<JLabel>(); for(int i=0; i<jLabels.length; i++){ for(int j=0; j<jLabels[i].length; j++){ findWords(jLabels[i][j].getText(), i, j, labelsUsed); //System.out.println("Done"); } } } edit: BTW I am using a GUI and the letters on the board are displayed by using a JLabel.

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• sql query is too slow, how to improve speed

  - by user1289282

  I have run into a bottleneck when trying to update one of my tables. The player table has, among other things, id, skill, school, weight. What I am trying to do is: SELECT id, skill FROM player WHERE player.school = (current school of 4500) AND player.weight = (current weight of 14) to find the highest skill of all players returned from the query UPDATE player SET starter = 'TRUE' WHERE id = (highest skill) move to next weight and repeat when all weights have been completed move to next school and start over all schools completed, done I have this code implemented and it works, but I have approximately 4500 schools totaling 172000 players and the way I have it now, it would take probably a half hour or more to complete (did not wait it out), which is way too slow. How to speed this up? Short of reducing the scale of the system, I am willing to do anything that gets the intended result. Thanks! *the weights are the standard folk style wrestling weights ie, 103, 113, 120, 126, 132, 138, 145, 152, 160, 170, 182, 195, 220, 285 pounds

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• What is microbenchmarking?

  - by polygenelubricants

  I've heard this term used, but I'm not entirely sure what it means, so: What DOES it mean and what DOESN'T it mean? What are some examples of what IS and ISN'T microbenchmarking? What are the dangers of microbenchmarking and how do you avoid it? (or is it a good thing?)

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• How to explain to a developer that adding extra if - else if conditions is not a good way to "improv

  - by Lilit

  Recently I've bumped into the following C++ code: if (a) { f(); } else if (b) { f(); } else if (c) { f(); } Where a, b and c are all different conditions, and they are not very short. I tried to change the code to: if (a || b || c) { f(); } But the author opposed saying that my change will decrease readability of the code. I had two arguments: 1) You should not increase readability by replacing one branching statement with three (though I really doubt that it's possible to make code more readable by using else if instead of ||). 2) It's not the fastest code, and no compiler will optimize this. But my arguments did not convince him. What would you tell a programmer writing such a code? Do you think complex condition is an excuse for using else if instead of OR?

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• Best way to get distinct values from large table

  - by derivation

  I have a db table with about 10 or so columns, two of which are month and year. The table has about 250k rows now, and we expect it to grow by about 100-150k records a month. A lot of queries involve the month and year column (ex, all records from march 2010), and so we frequently need to get the available month and year combinations (ie do we have records for april 2010?). A coworker thinks that we should have a separate table from our main one that only contains the months and years we have data for. We only add records to our main table once a month, so it would just be a small update on the end of our scripts to add the new entry to this second table. This second table would be queried whenever we need to find the available month/year entries on the first table. This solution feels kludgy to me and a violation of DRY. What do you think is the correct way of solving this problem? Is there a better way than having two tables?

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• SQL Server - Missing Indexes - What would use the index?

  - by BankZ

  I am using SQL Server 2008 and we are using the DMV's to find missing indexes. However, before I create the new index I am trying to figure out what proc/query is wanting that index. I want the most information I can get so I can make informed decision on my indexes. Sometimes the indexes SQL Server wants does not make sense to me. Does anyone know how I can figure out what wants it?

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• PHP : flatten array - fastest way?

  - by Industrial

  Is there any fast way to flatten an array and select subkeys ('key'&'value' in this case) without running a foreach loop, or is the foreach always the fastest way? Array ( [0] => Array ( [key] => string [value] => a simple string [cas] => 0 ) [1] => Array ( [key] => int [value] => 99 [cas] => 0 ) [2] => Array ( [key] => array [value] => Array ( [0] => 11 [1] => 12 ) [cas] => 0 ) ) To: Array ( [int] => 99 [string] => a simple string [array] => Array ( [0] => 11 [1] => 12 ) )

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• Django: IE doesn't load locahost or loads very SLOWLY

  - by reedvoid

  I'm just starting to learn Django, building a project on my computer, running Windows 7 64-bit, Python 2.7, Django 1.3. Basically whatever I write, it loads in Chrome and Firefox instantly. But for IE (version 9), it just stalls there, and does nothing. I can load up "http://127.0.0.1:8000" on IE and leave the computer on for hours and it doesn't load. Sometimes, when I refresh a couple of times or restart IE it'll work. If I change something in the code, again, Chrome and Firefox reflects changes instantly, whereas IE doesn't - if it loads the page at all. What is going on? I'm losing my mind here....

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• Using FILE_FLAG_NO_BUFFERING will return noticeable speed gain?

  - by 9dan

  Recently noticed detail description of FILE_FLAG_NO_BUFFERING flag in MSDN, and read several Google search results about unbuffered I/O in Windows. http://msdn.microsoft.com/en-us/library/aa363858(v=vs.85).aspx I wondering now, is it really important to consider unbuffered option in file I/O programming? Because many programs use plain old C stream I/O or C++ iostream, I didn't gave any attention to FILE_FLAG_NO_BUFFERING flag before. Let's say we are developing photo explorer program like Picasa. If we implement unbuffered I/O, could thumbnail display speed show noticeable difference in ordinary users?

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• Nested loop traversing arrays

  - by alecco

  There are 2 very big series of elements, the second 100 times bigger than the first. For each element of the first series, there are 0 or more elements on the second series. This can be traversed and processed with 2 nested loops. But the unpredictability of the amount of matching elements for each member of the first array makes things very, very slow. The actual processing of the 2nd series of elements involves logical and (&) and a population count. I couldn't find good optimizations using C but I am considering doing inline asm, doing rep* mov* or similar for each element of the first series and then doing the batch processing of the matching bytes of the second series, perhaps in buffers of 1MB or something. But the code would be get quite messy. Does anybody know of a better way? C preferred but x86 ASM OK too. Many thanks! Sample/demo code with simplified problem, first series are "people" and second series are "events", for clarity's sake. (the original problem is actually 100m and 10,000m entries!) #include <stdio.h> #include <stdint.h> #define PEOPLE 1000000 // 1m struct Person { uint8_t age; // Filtering condition uint8_t cnt; // Number of events for this person in E } P[PEOPLE]; // Each has 0 or more bytes with bit flags #define EVENTS 100000000 // 100m uint8_t P1[EVENTS]; // Property 1 flags uint8_t P2[EVENTS]; // Property 2 flags void init_arrays() { for (int i = 0; i < PEOPLE; i++) { // just some stuff P[i].age = i & 0x07; P[i].cnt = i % 220; // assert( sum < EVENTS ); } for (int i = 0; i < EVENTS; i++) { P1[i] = i % 7; // just some stuff P2[i] = i % 9; // just some other stuff } } int main(int argc, char *argv[]) { uint64_t sum = 0, fcur = 0; int age_filter = 7; // just some init_arrays(); // Init P, P1, P2 for (int64_t p = 0; p < PEOPLE ; p++) if (P[p].age < age_filter) for (int64_t e = 0; e < P[p].cnt ; e++, fcur++) sum += __builtin_popcount( P1[fcur] & P2[fcur] ); else fcur += P[p].cnt; // skip this person's events printf("(dummy %ld %ld)\n", sum, fcur ); return 0; } gcc -O5 -march=native -std=c99 test.c -o test

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