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• Javascript Graph Layout Engine

  - by GJK

  I'm looking for a Javascript library/engine that can do graph layouts. (And when I say layouts, I mean logically position vertices nicely.) The graphs I'm working with are all m-ary trees. M is usually no more than 5 or 6, but it can be greater in some cases. I do have something that I use now, Graphviz's node program, and it works perfectly. The problem is, when running a web app, I have to send a request to the server every time I want a layout. Preferably, I would like something written in Javascript that can be quickly run on the client side. All it needs to do is provide layout information (relative positioning and whatnot). I don't need it to draw to a canvas or use SVG or anything, all I'm interested in is the layout. Library use like jQuery or RaphaelJS is fine by me. I'll work with it. I'm just looking for something to speed things along a little. Also, I'd consider writing my own if I could find a nice description of an algorithm to do the layouts. But I really don't want to spend too much time. I have something that works now, so getting it on the client side is just a bonus, not a necessity.

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• Create a variable which is named depending on an ID number?

  - by gray

  Is there any way to create a variable, and add an ID to the end of the actual variable name? I have a variable called 'gauge', used to create a new Gauge object: var gauge = new Gauge(target).setOptions(opts); I want to add an ID to the variable, so something like: var gauge+id = new Gauge(target).setOptions(opts); It's because I'm creating a number of these objects, and have a specific ID already for each one, which I want to attach to the gauge object if possible? All my code for this function is below, if it gives you a better idea of what i need to do: function go(id, votes) { var val = $('#votes_'+id).text(); var target = document.getElementById('foo_'+id); // your canvas element var gauge = new Gauge(target).setOptions(opts); // create sexy gauge! gauge.maxValue = 100; // set max gauge value gauge.animationSpeed = 20; // set animation speed (32 is default value) var a=votes+0.5; gauge.set(val); // set actual value } My main problem arises on the last line. It says gauge.set(val), and it only sets the last object, ignoring all the other ones...

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• Currently using View, Should I use a hard table instead?

  - by 1001010101

  I am currently debating whether my table, mapping_uGroups_uProducts, which is a view formed by the following table: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `db`.`mapping_uGroups_uProducts` AS select distinct `X`.`upID` AS `upID`,`Z`.`ugID` AS `ugID` from ((`db`.`mapping_uProducts_Products` `X` join `db`.`productsInfo` `Y` on((`X`.`pID` = `Y`.`pID`))) join `db`.`mapping_uGroups_Groups` `Z` on((`Y`.`gID` = `Z`.`gID`))); My current query is: SELECT upID FROM uProductsInfo \ JOIN fs_uProducts USING (upID) column \ JOIN mapping_uGroups_uProducts USING (upID) -- could be faster if we use hard table and index \ JOIN mapping_fs_key USING (fsKeyID) \ WHERE fsName="OVERALL" \ AND ugID=1 \ ORDER BY score DESC \ LIMIT 0,30; which is pretty slow. (for 30 results, it requires about 10 secondes). I think the reason for my query being so slow is definitely due to the fact that that particular query relies on a VIEW which has no index to speed things up. +----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+ | 1 | PRIMARY | mapping_fs_key | const | PRIMARY,fsName | fsName | 386 | const | 1 | Using temporary; Using filesort | | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 19706 | Using where | | 1 | PRIMARY | uProductsInfo | eq_ref | PRIMARY | PRIMARY | 4 | mapping_uGroups_uProducts.upID | 1 | Using index | | 1 | PRIMARY | fs_uProducts | ref | upID | upID | 4 | db.uProductsInfo.upID | 221 | Using where | | 2 | DERIVED | X | ALL | PRIMARY | NULL | NULL | NULL | 40772 | Using temporary | | 2 | DERIVED | Y | eq_ref | PRIMARY | PRIMARY | 4 | db.X.pID | 1 | Distinct | | 2 | DERIVED | Z | ref | PRIMARY | PRIMARY | 4 | db.Y.gID | 2 | Using index; Distinct | +----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+ 7 rows in set (0.48 sec) The explain here looks pretty cryptic, and I don't know whether I should drop view and write a script to just insert everything in the view to a hard table. ( obviously, it will lose the flexibility of the view since the mapping changes quite frequently). Does anyone have any idea to how I can optimize my schema better?

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• fastest way to check to see if a certain index in a linq statement is null

  - by tehdoommarine

  Basic Details I have a linq statement that grabs some records from a database and puts them in a System.Linq.Enumerable: var someRecords = someRepoAttachedToDatabase.Where(p=>true); Suppose this grabs tons (25k+) of records, and i need to perform operations on all of them. to speed things up, I have to decided to use paging and perform the operations needed in blocks of 100 instead of all of the records at the same time. The Question The line in question is the line where I count the number of records in the subset to see if we are on the last page; if the number of records in subset is less than the size of paging - then that means there are no more records left. What I would like to know is what is the fastest way to do this? Code in Question int pageSize = 100; bool moreData = true; int currentPage = 1; while (moreData) { var subsetOfRecords = someRecords.Skip((currentPage - 1) * pageSize).Take(pageSize); //this is also a System.Linq.Enumerable if (subsetOfRecords.Count() < pageSize){ moreData = false;} //line in question //do stuff to records in subset currentPage++; } Things I Have Considered subsetOfRecords.Count() < pageSize subsetOfRecords.ElementAt(pageSize - 1) == null (causes out of bounds exception - can catch exception and set moreData to false there) Converting subsetOfRecords to an array (converting someRecords to an array will not work due to the way subsetOfRecords is declared - but I am open to changing it) I'm sure there are plenty of other ideas that I have missed.

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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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• Optimize SQL connection?

  - by user1484035

  I am building a multi-page web project in HTML and Javascript that is constantly reading from AND writing to an SQL database. I can connect to the database and successfully run my project with this type of connection. var connection = new ActiveXObject("ADODB.Connection") ; var connectionstring="Data Source=<server>;Initial Catalog=<catalog>;User ID=<user>; Password=<password>;Provider=SQLOLEDB"; connection.Open(connectionstring); var rs = new ActiveXObject("ADODB.Recordset"); rs.Open("SELECT * FROM table", connection); rs.MoveFirst while(!rs.eof) { document.write(rs.fields(1)); rs.movenext; } rs.close; connection.close; Works great and runs fine. BUT, the first 5 lines (from var connection = to var rs =) causes the whole browser to freeze for a few seconds while it establishes the connection. I need to speed that up since I am constantly connecting to the database throughout my project. Is there a more effective way of connecting to a SQL database? or is my computer just bad and this should run faster?

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• Is there a recommended way to communicate scientific/engineering programming to C developers?

  - by ggkmath

  Hi, I have a lot of MATLAB code that needs to get ported to C (execution speed is critical for this work) as part of a back-end process for a web application. When I attempt to outsource this code to a C developer, I assume (correct me if I'm wrong) few C developers also understand MATLAB code (things like indexing and memory management are different, etc.). I wonder if there are any C developers out there that can recommend a procedure for me to follow to best communicate what the code does? For example, should I provide the MATLAB code and explain what it's doing line by line? Or, should I just provide the math/algorithm, explain it in plain English, and let the C developer implement it with this understanding in his/her own way (e.g. can I assume the developer understands how to work with complex math (i.e. imaginary numbers), how to generate histograms, perform an FFT, etc.)? Or, is there a better method? I expect I'm not the first to need to do this, so I wonder if any C developers out there ran into this situation and can share any conventional wisdom how they'd like this task to be transferred? Thanks in advance for any comments.

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• What are CAD apps written in, and how are they organized ?

  - by ldigas

  What are CAD applications (Rhino, Autocad) of today written in and how are they organized internally ? I gave as an example, Autocad and Rhino, although I would love to hear of other examples as well. I'm particularly interested in knowing what is their backend written in (multilanguage ?) and how is it organized, and how do they handle their frontend (GUI) in real time ? Do they use native windows API's or some libraries of their own, since I imagine, as good as may be, the open source solutions on today's market won't cut it. I may be wrong ... As most of you who have used them know, they handle amongs other things relatively complex rotational operations in realtime (shading is not interesting me). I've been doing some experiments with several packages recently, and for some larger models found that there is considerable difference in speed in, for example, programed rotation (big full ship models) amongst some of them (which I won't name). So I'm wondering about their internals ... Also, if someone knows of some book on the subject, I'd be interested to hear of it.

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• Tricky SQL query - need to get time frames

  - by Andrew

  I am stumbled upon a problem, when I need a query which will produce a list of speeding time frames. Here is the data example [idgps_unit_location] [dt] [idgps_unit] [lat] [long] [speed_kmh] 26 10/18/2012 18:53 2 47 56 30 27 10/18/2012 18:53 2 49 58 31 28 10/18/2012 18:53 2 28 37 15 29 10/18/2012 18:54 2 56 65 33 30 10/18/2012 18:54 2 152 161 73 31 10/18/2012 18:55 2 134 143 64 32 10/18/2012 18:56 2 22 31 12 36 10/18/2012 18:59 2 98 107 47 37 10/18/2012 18:59 2 122 131 58 38 10/18/2012 18:59 2 91 100 44 39 10/18/2012 19:00 2 190 199 98 40 10/18/2012 19:01 2 194 203 101 41 10/18/2012 19:02 2 182 191 91 42 10/18/2012 19:03 2 162 171 78 43 10/18/2012 19:03 2 174 183 83 44 10/18/2012 19:04 2 170 179 81 45 10/18/2012 19:05 2 189 198 97 46 10/18/2012 19:06 2 20 29 10 47 10/18/2012 19:07 2 158 167 76 48 10/18/2012 19:08 2 135 144 64 49 10/18/2012 19:08 2 166 175 79 50 10/18/2012 19:09 2 9 18 5 51 10/18/2012 19:09 2 101 110 48 52 10/18/2012 19:09 2 10 19 7 53 10/18/2012 19:10 2 32 41 20 54 10/18/2012 19:10 1 54 63 85 55 10/19/2012 19:11 2 55 64 50 I need a query that would convert this table into the following report that shows frames of time when speed was 80: [idgps_unit] [dt_start] [lat_start] [long_start] [speed_start] [dt_end] [lat_end] [long_end] [speed_end] [speed_average] 2 10/18/2012 19:00 190 199 98 10/18/2012 19:02 182 191 91 96.66666667 2 10/18/2012 19:03 174 183 83 10/18/2012 19:05 189 198 97 87 1 10/18/2012 19:10 54 63 85 10/18/2012 19:10 54 63 85 85 Now, what have I tried? I tried putting this into separate tables, queries and do some joins... Nothing works and I am very frustrated... I am not even sure if this could be done via the query. Asking for the expert help!

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• Using static variables for Strings

  - by Vivart

  below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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• How to do an additional search on archive in rails if record not found, by extending model?

  - by Nick Gorbikoff

  Hello, I was wondering if somebody knows an elegant solution to the following: Suppose I have a table that holds orders, with a bunch of data. So I'm at 1M records, and searches begin to take time. So I want to speed it up by archiving some data that is more than 3 years old - saving it into a table called orders-archive, and then purging them from the orders table. So if we need to research something or customer wants to pull older information - they still can, but 99% of the lookups are done on the orders no older than a year and a half - so there is no reason to keep looking through older data all the time. These move & purge operations can be then croned to be done on a weekly basis. I already did some tests and I know that I will slash my search times by about 4 times. So far so good, right? However I was thinking about how to implement older archival lookups and the only reasonable thing I can think of is some sort of if-else If not found in orders, do a search in orders-archive. However - I have about 20 tables that I want to archive and god knows how many searches / finds are done through out the code, that I don't want to modify. So I was wondering if there is an elegant rails-way solution to this problem, by extending a model somehow? Has anyone dealt with similar case before? Thank you.

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• Which is the correct design pattern for my PHP application?

  - by user1487141

  I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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• Gradual memory leak and slowdown in loop

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases, and the speed at which frames are processed drops precipitously. (From ~0.5 seconds per frame at the start, to ~2 seconds per frame by the 250th frame.) The only thing I can think can be causing the gradual memory leak is a buildup of the NSAutoreleasePool objects themselves. Am I right in thinking they will only be deallocated when the outer pool is released? If so, is there a better memory management solution here? Creating a pool every run through the loop seems a little hacky. And if not, what is causing the slow memory leak? (It is not NSStrings, and much too slow to be NSImages or NSDatas.) And what could be causing the slowdown?

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• Is there a reason why SSIS significantly slows down after a few minutes?

  - by Mark

  I'm running a fairly substantial SSIS package against SQL 2008 - and I'm getting the same results both in my dev environment (Win7-x64 + SQL-x64-Developer) and the production environment (Server 2008 x64 + SQL Std x64). The symptom is that initial data loading screams at between 50K - 500K records per second, but after a few minutes the speed drops off dramatically and eventually crawls embarrasingly slowly. The database is in Simple recovery model, the target tables are empty, and all of the prerequisites for minimally logged bulk inserts are being met. The data flow is a simple load from a RAW input file to a schema-matched table (i.e. no complex transforms of data, no sorting, no lookups, no SCDs, etc.) The problem has the following qualities and resiliences: Problem persists no matter what the target table is. RAM usage is lowish (45%) - there's plenty of spare RAM available for SSIS buffers or SQL Server to use. Perfmon shows buffers are not spooling, disk response times are normal, disk availability is high. CPU usage is low (hovers around 25% shared between sqlserver.exe and DtsDebugHost.exe) Disk activity primarily on TempDB.mdf, but I/O is very low (< 600 Kb/s) OLE DB destination and SQL Server Destination both exhibit this problem. To sum it up, I expect either disk, CPU or RAM to be exhausted before the package slows down, but instead its as if the SSIS package is taking an afternoon nap. SQL server remains responsive to other queries, and I can't find any performance counters or logged events that betray the cause of the problem. I'll gratefully reward any reasonable answers / suggestions.

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• read files from directory and filter files from Java

  - by Adnan

  The following codes goes through all directories and sub-directories and outputs just .java files; import java.io.File; public class DirectoryReader { private static String extension = "none"; private static String fileName; public static void main(String[] args ){ String dir = "C:/tmp"; File aFile = new File(dir); ReadDirectory(aFile); } private static void ReadDirectory(File aFile) { File[] listOfFiles = aFile.listFiles(); if (aFile.isDirectory()) { listOfFiles = aFile.listFiles(); if(listOfFiles!=null) { for(int i=0; i < listOfFiles.length; i++ ) { if (listOfFiles[i].isFile()) { fileName = listOfFiles[i].toString(); int dotPos = fileName.lastIndexOf("."); if (dotPos > 0) { extension = fileName.substring(dotPos); } if (extension.equals(".java")) { System.out.println("FILE:" + listOfFiles[i] ); } } if(listOfFiles[i].isDirectory()) { ReadDirectory(listOfFiles[i]); } } } } } } Is this efficient? What could be done to increase the speed? All ideas are welcome.

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• A scripting engine for Ruby?

  - by Earlz

  Hello, I am creating a Ruby On Rails website, and for one part it needs to be dynamic so that (sorta) trusted users can make parts of the website work differently. For this, I need a scripting language. In a sort of similar project in ASP.Net, I wrote my own scripting language/DSL. I can not use that source code(written at work) though, and I don't want to make another scripting language if I don't have to. So, what choices do I have? The scripting must be locked down and not be able to crash my server or anything. I'd really like if I could use Ruby as the scripting language, but it's not strictly necessary. Also, this scripting part will be called on almost every request for the website, sometimes more than once. So, speed is a factor. I looked at the RubyLuaBridge but it is Alpha status and seems dead. What choices for a scripting language do I have in a Ruby project? Also, I will have full control over where this project is deployed(root access), so there are no real limits..

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• What is the fastest way to check if files are identical?

  - by ojblass

  If you have 1,000,0000 source files, you suspect they are all the same, and you want to compare them what is the current fasted method to compare those files? Assume they are Java files and platform where the comparison is done is not important. cksum is making me cry. When I mean identical I mean ALL identical. Update: I know about generating checksums. diff is laughable ... I want speed. Update: Don't get stuck on the fact they are source files. Pretend for example you took a million runs of a program with very regulated output. You want to prove all 1,000,000 versions of the output are the same. Update: read the number of blocks rather than bytes? Immediatly throw out those? Is that faster than finding the number of bytes? Update: Is this ANY different than the fastest way to compare two files?

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• Determining Best Table Structure for MySQL Performance

  - by Joe Majewski

  I'm working on a browser-based RPG for one of my websites, and right now I'm trying to determine the best way to organize my SQL tables for performance and maintenance. Here's my question: Does the number of columns in an SQL table affect the speed in which it can be queried? I am not a newbie when it comes to PHP or MySQL. I used to develop things with the common goal of getting them to work, but I've recently advanced to the stage where a functional program is not good enough unless it's fast and reliable. Anyways, right now I have a members table that has around 15 columns. It contains information such as the player's username, password, email, logins, page views, etcetera. It doesn't contain any information on the player's progress in the game, however. If I added columns for things such as army size, gold, turns, and whatnot, then it could easily rise to around 40 or 50 total columns. Oh, and my database structure IS normalized. Will a table with 50 columns that gets constantly queried be a bad idea? Should I split it into two tables; one for the user's general information and one for the user's game statistics? I know I could check the query time myself, but I haven't actually created the tables yet and I think I'd be better off with some professional advice on this important decision for my game. Thank you for your time! :)

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• I need to make a multithreading program (python)

  - by Andreawu98

  import multiprocessing import time from itertools import product out_file = open("test.txt", 'w') P = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p','q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',] N = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] M = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'] c = int(input("Insert the number of digits you want: ")) n = int(input("If you need number press 1: ")) m = int(input("If you need upper letters press 1: ")) i = [] if n == 1: P = P + N if m == 1: P = P + M then = time.time() def worker(): for i in product(P, repeat=c): #check every possibilities k = '' for z in range(0, c): # k = k + str(i[z]) # print each possibility in a txt without parentesis or comma out_file.write( k + '\n') # out_file.close() now = time.time() diff = str(now - then) # To see how long does it take print(diff) worker() time.sleep(10) # just to check console The code check every single possibility and print it out in a test.txt file. It works but I really can't understand how can I speed it up. I saw it use 1 core out of my quad core CPU so I thought Multi-threading might work even though I don't know how. Please help me. Sorry for my English, I am from Italy.

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• Approach for caching data from data logger

  - by filip-fku

  Greetings, I've been working on a C#.NET app that interacts with a data logger. The user can query and obtain logs for a specified time period, and view plots of the data. Typically a new data log is created every minute and stores a measurement for a few parameters. To get meaningful information out of the logger, a reasonable number of logs need to be acquired - data for at least a few days. The hardware interface is a UART to USB module on the device, which restricts transfers to a maximum of about 30 logs/second. This becomes quite slow when reading in the data acquired over a number of days/weeks. What I would like to do is improve the perceived performance for the user. I realize that with the hardware speed limitation the user will have to wait for the full download cycle at least the first time they acquire a larger set of data. My goal is to cache all data seen by the app, so that it can be obtained faster if ever requested again. The approach I have been considering is to use a light database, like SqlServerCe, that can store the data logs as they are received. I am then hoping to first search the cache prior to querying a device for logs. The cache would be updated with any logs obtained by the request that were not already cached. Finally my question - would you consider this to be a good approach? Are there any better alternatives you can think of? I've tried to search SO and Google for reinforcement of the idea, but I mostly run into discussions of web request/content caching. Thanks for any feedback!

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• What hash algorithms are parallelizable? Optimizing the hashing of large files utilizing on multi-co

  - by DanO

  I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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• Optimizing a "set in a string list" to a "set as a matrix" operation

  - by Eric Fournier

  I have a set of strings which contain space-separated elements. I want to build a matrix which will tell me which elements were part of which strings. For example: "" "A B C" "D" "B D" Should give something like: A B C D 1 2 1 1 1 3 1 4 1 1 Now I've got a solution, but it runs slow as molasse, and I've run out of ideas on how to make it faster: reverseIn <- function(vector, value) { return(value %in% vector) } buildCategoryMatrix <- function(valueVector) { allClasses <- c() for(classVec in unique(valueVector)) { allClasses <- unique(c(allClasses, strsplit(classVec, " ", fixed=TRUE)[[1]])) } resMatrix <- matrix(ncol=0, nrow=length(valueVector)) splitValues <- strsplit(valueVector, " ", fixed=TRUE) for(cat in allClasses) { if(cat=="") { catIsPart <- (valueVector == "") } else { catIsPart <- sapply(splitValues, reverseIn, cat) } resMatrix <- cbind(resMatrix, catIsPart) } colnames(resMatrix) <- allClasses return(resMatrix) } Profiling the function gives me this: $by.self self.time self.pct total.time total.pct "match" 31.20 34.74 31.24 34.79 "FUN" 30.26 33.70 74.30 82.74 "lapply" 13.56 15.10 87.86 97.84 "%in%" 12.92 14.39 44.10 49.11 So my actual questions would be: - Where are the 33% spent in "FUN" coming from? - Would there be any way to speed up the %in% call? I tried turning the strings into factors prior to going into the loop so that I'd be matching numbers instead of strings, but that actually makes R crash. I've also tried going for partial matrix assignment (IE, resMatrix[i,x] <- 1) where i is the number of the string and x is the vector of factors. No dice there either, as it seems to keep on running infinitely.

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• Faster Insertion of Records into a Table with SQLAlchemy

  - by Kyle Brandt

  I am parsing a log and inserting it into either MySQL or SQLite using SQLAlchemy and Python. Right now I open a connection to the DB, and as I loop over each line, I insert it after it is parsed (This is just one big table right now, not very experienced with SQL). I then close the connection when the loop is done. The summarized code is: log_table = schema.Table('log_table', metadata, schema.Column('id', types.Integer, primary_key=True), schema.Column('time', types.DateTime), schema.Column('ip', types.String(length=15)) .... engine = create_engine(...) metadata.bind = engine connection = engine.connect() .... for line in file_to_parse: m = line_regex.match(line) if m: fields = m.groupdict() pythonified = pythoninfy_log(fields) #Turn them into ints, datatimes, etc if use_sql: ins = log_table.insert(values=pythonified) connection.execute(ins) parsed += 1 My two questions are: Is there a way to speed up the inserts within this basic framework? Maybe have a Queue of inserts and some insertion threads, some sort of bulk inserts, etc? When I used MySQL, for about ~1.2 million records the insert time was 15 minutes. With SQLite, the insert time was a little over an hour. Does that time difference between the db engines seem about right, or does it mean I am doing something very wrong?

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• Looking for a good C++/.net

  - by Michael Minerva

  I have recently started to feel that I need to greatly improve my C++ skills especially in the realm of .net. I graduated from a good four year university with a degree in computer science about 9 months ago and I have since been doing full time contract work for a small software company in my local area. Most of my work has been done using Java/lisp/cocoa/XML and before that most of my programming in my senior year was in java/C#. I did a decent amount of C++ in my Sophomore year and in my free time before that but I feel that my general knowledge of C++/.net is very lacking for the opportunities that are now coming my way. Can anyone recommend a good book that could help me get up too speed? I feel I do not need a very basic introduction to C++ but something that covers the fundamentals of .net would be good for me. So basically what I need is a book or books that would be good for a .net novice and a C++ developer who is just beyond novice. Also, a book that would help bein an interview by giving me a conversional understanding of C++ would be great. Thanks a lot!.

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