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  • Efficient way to delete a line from a text file (C#)

    - by Valentin Vasilyev
    Hello. I need to delete a certain line from a text file. What is the most efficient way of doing this? File can be potentially large(over million records). Thank you. UPDATE: below is the code I'm currently using, but I'm not sure if it is good. internal void DeleteMarkedEntries() { string tempPath=Path.GetTempFileName(); using (var reader = new StreamReader(logPath)) { using (var writer = new StreamWriter(File.OpenWrite(tempPath))) { int counter = 0; while (!reader.EndOfStream) { if (!_deletedLines.Contains(counter)) { writer.WriteLine(reader.ReadLine()); } ++counter; } } } if (File.Exists(tempPath)) { File.Delete(logPath); File.Move(tempPath, logPath); } }

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  • How to get the size of a binary tree ?

    - by Andrei Ciobanu
    I have a very simple binary tree structure, something like: struct nmbintree_s { unsigned int size; int (*cmp)(const void *e1, const void *e2); void (*destructor)(void *data); nmbintree_node *root; }; struct nmbintree_node_s { void *data; struct nmbintree_node_s *right; struct nmbintree_node_s *left; }; Sometimes i need to extract a 'tree' from another and i need to get the size to the 'extracted tree' in order to update the size of the initial 'tree' . I was thinking on two approaches: 1) Using a recursive function, something like: unsigned int nmbintree_size(struct nmbintree_node* node) { if (node==NULL) { return(0); } return( nmbintree_size(node->left) + nmbintree_size(node->right) + 1 ); } 2) A preorder / inorder / postorder traversal done in an iterative way (using stack / queue) + counting the nodes. What approach do you think is more 'memory failure proof' / performant ? Any other suggestions / tips ? NOTE: I am probably going to use this implementation in the future for small projects of mine. So I don't want to unexpectedly fail :).

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  • Tuning JVM (GC) for high responsive server application

    - by elgcom
    I am running an application server on Linux 64bit with 8 core CPUs and 6 GB memory. The server must be highly responsive. After some inspection I found that the application running on the server creates rather a huge amount of short-lived objects, and has only about 200~400 MB long-lived objects(as long as there is no memory leak) After reading http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html I use these JVM options -Xms2g -Xmx2g -XX:MaxPermSize=256m -XX:NewRatio=1 -XX:+UseConcMarkSweepGC Result: the minor GC takes 0.01 ~ 0.02 sec, the major GC takes 1 ~ 3 sec the minor GC happens constantly. How can I further improve or tune the JVM? larger heap size? but will it take more time for GC? larger NewSize and MaxNewSize (for young generation)? other collector? parallel GC? is it a good idea to let major GC take place more often? and how?

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  • one two-directed tcp socket of two one-directed? (linux, high volume, low latency)

    - by osgx
    Hello I need to send (interchange) a high volume of data periodically with the lowest possible latency between 2 machines. The network is rather fast (e.g. 1Gbit or even 2G+). Os is linux. Is it be faster with using 1 tcp socket (for send and recv) or with using 2 uni-directed tcp sockets? The test for this task is very like NetPIPE network benchmark - measure latency and bandwidth for sizes from 2^1 up to 2^13 bytes, each size sent and received 3 times at least (in teal task the number of sends is greater. both processes will be sending and receiving, like ping-pong maybe). The benefit of 2 uni-directed connections come from linux: http://lxr.linux.no/linux+v2.6.18/net/ipv4/tcp_input.c#L3847 3847/* 3848 * TCP receive function for the ESTABLISHED state. 3849 * 3850 * It is split into a fast path and a slow path. The fast path is 3851 * disabled when: ... 3859 * - Data is sent in both directions. Fast path only supports pure senders 3860 * or pure receivers (this means either the sequence number or the ack 3861 * value must stay constant) ... 3863 * 3864 * When these conditions are not satisfied it drops into a standard 3865 * receive procedure patterned after RFC793 to handle all cases. 3866 * The first three cases are guaranteed by proper pred_flags setting, 3867 * the rest is checked inline. Fast processing is turned on in 3868 * tcp_data_queue when everything is OK. All other conditions for disabling fast path is false. And only not-unidirected socket stops kernel from fastpath in receive

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  • Prepending to a multi-gigabyte file.

    - by dafmetal
    What would be the most performant way to prepend a single character to a multi-gigabyte file (in my practical case, a 40GB file). There is no limitation on the implementation to do this. Meaning it can be through a tool, a shell script, a program in any programming language, ...

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  • Should I go with Varnish instead of nginx?

    - by gotts
    I really like nginx. But recently I've found that varnish gives you an opportunity to implement smart caching revers proxy layer(with URL purging). I have a cluster of mongrels which are pretty resource-intensive so if this caching layer can remove some load from mongrels this can be a great thing. I didn't find a way to implement the caching layer(with for application pages; static content is cacheable of course) same with nginx.. Should I use Varnish instead? What would you recommend?

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  • What runs faster? Wordpress or Drupal 6.x?

    - by electblake
    So... I run a pretty large Wordpress blog. Currently it gets around 20k+ pageviews a day, and its always a struggle to keep the bad boy running quickly - I currently run a vps.net with CentOS 5.3 I am also Drupal developer by trade so I love the CMS Framework for its versatility and the portability (I can take work from one site and implement on another with great ease) MY QUESTION IS: What is faster then? Wordpress 3.x & Drupal 6.x I'd love to migrate my site to Drupal to be able to roll out new features etc (which I find awkward to do in Wordpress) but I am scared that Drupal may not be able to handle the traffic. Any opinions? I know that some major players use Drupal - as Dries documents well on his blog but I'm not under any illusions that Drupal can be a real hog. Thanks for any/all help! Please try to avoid server optimization talk unless it pertains to Wordpress or Drupal 6.x specifically, I love to learn more about optimizations but I do want to sort out which platform is quicker :) p.s - I realize the fastest option is to use a lower-level framework (with less overhead) like CakePHP etc but assume that isn't an option ;)

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  • Django: Update order attribute for objects in a queryset

    - by lazerscience
    I'm having a attribute on my model to allow the user to order the objects. I have to update the element's order depending on a list, that contains the object's ids in the new order; right now I'm iterating over the whole queryset and set one objects after the other. What would be the easiest/fastest way to do the same with the whole queryset? def update_ordering(model, order): """ order is in the form [id,id,id,id] for example: [8,4,5,1,3] """ id_to_order = dict((order[i], i) for i in range(len(order))) for x in model.objects.all(): x.order = id_to_order[x.id] x.save()

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  • Sql Server 2000 Stored Procedure Prevent 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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  • integer division in php

    - by oezi
    hi guys, i'm looking for the fastest way to do an integer division in php. for example, 5 / 2 schould be 4 | 6 / 2 should be 3 and so on. if i simply do this, php will return 2.5 in the first case, the only solution i could find was using intval($my_number/2) - wich isn't as fast as i want it to be (but gives the expected results). can anyone help me out with this?

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  • How to copy files without slowing down my app?

    - by Kevin Gebhardt
    I have a bunch of little files in my assets which need to be copied to the SD-card on the first start of my App. The copy code i got from here placed in an IntentService works like a charm. However, when I start to copy many litte files, the whole app gets increddible slow (I'm not really sure why by the way), which is a really bad experience for the user on first start. As I realised other apps running normal in that time, I tried to start a child process for the service, which didn't work, as I can't acess my assets from another process as far as I understood. Has anybody out there an idea how a) to copy the files without blocking my app b) to get through to my assets from a private process (process=":myOtherProcess" in Manifest) or c) solve the problem in a complete different way Edit: To make this clearer: The copying allready takes place in a seperate thread (started automaticaly by IntentService). The problem is not to separate the task of copying but that the copying in a dedicated thread somehow affects the rest of the app (e.g. blocking to many app-specific resources?) but not other apps (so it's not blocking the whole CPU or someting) Edit2: Problem solved, it turns out, there wasn't really a problem. See my answer below.

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  • Definition of Connect, Processing, Waiting in apache bench.

    - by rpatel
    When I run apache bench I get results like: Command: abs.exe -v 3 -n 10 -c 1 https://mysite Connection Times (ms) min mean[+/-sd] median max Connect: 203 213 8.1 219 219 Processing: 78 177 88.1 172 359 Waiting: 78 169 84.6 156 344 Total: 281 389 86.7 391 563 I can't seem to find the definition of Connect, Processing and Waiting. What do those numbers mean?

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  • Database structure for ecommerce site

    - by imanc
    Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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  • SQL Server uncorrelated subquery very slow

    - by brianberns
    I have a simple, uncorrelated subquery that performs very poorly on SQL Server. I'm not very experienced at reading execution plans, but it looks like the inner query is being executed once for every row in the outer query, even though the results are the same each time. What can I do to tell SQL Server to execute the inner query only once? The query looks like this: select * from Record record0_ where record0_.RecordTypeFK='c2a0ffa5-d23b-11db-9ea3-000e7f30d6a2' and ( record0_.EntityFK in ( select record1_.EntityFK from Record record1_ join RecordTextValue textvalues2_ on record1_.PK=textvalues2_.RecordFK and textvalues2_.FieldFK = '0d323c22-0ec2-11e0-a148-0018f3dde540' and (textvalues2_.Value like 'O%' escape '~') ) )

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  • oprofile unable to produce call graph

    - by aaa
    hello I am trying to use oprofile to generate call graph. Compiler is g++, platform is linux x86-64, linker is gfortran C++ code is compiled with -fno- omit-frame-pointer. oprofile is started with --callgraph=25. report I run with --callgraph. the call graph is produced but it's only includes self time, which is not much use what am I missing?

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  • one two-directed tcp socket OR two one-directed? (linux, high volume, low latency)

    - by osgx
    Hello I need to send (interchange) a high volume of data periodically with the lowest possible latency between 2 machines. The network is rather fast (e.g. 1Gbit or even 2G+). Os is linux. Is it be faster with using 1 tcp socket (for send and recv) or with using 2 uni-directed tcp sockets? The test for this task is very like NetPIPE network benchmark - measure latency and bandwidth for sizes from 2^1 up to 2^13 bytes, each size sent and received 3 times at least (in teal task the number of sends is greater. both processes will be sending and receiving, like ping-pong maybe). The benefit of 2 uni-directed connections come from linux: http://lxr.linux.no/linux+v2.6.18/net/ipv4/tcp_input.c#L3847 3847/* 3848 * TCP receive function for the ESTABLISHED state. 3849 * 3850 * It is split into a fast path and a slow path. The fast path is 3851 * disabled when: ... 3859 * - Data is sent in both directions. Fast path only supports pure senders 3860 * or pure receivers (this means either the sequence number or the ack 3861 * value must stay constant) ... 3863 * 3864 * When these conditions are not satisfied it drops into a standard 3865 * receive procedure patterned after RFC793 to handle all cases. 3866 * The first three cases are guaranteed by proper pred_flags setting, 3867 * the rest is checked inline. Fast processing is turned on in 3868 * tcp_data_queue when everything is OK. All other conditions for disabling fast path is false. And only not-unidirected socket stops kernel from fastpath in receive

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  • Tracking down slow managed DLL loading

    - by Alex K
    I am faced with the following issue and at this point I feel like I'm severely lacking some sort of tool, I just don't know what that tool is, or what exactly it should be doing. Here is the setup: I have a 3rd party DLL that has to be registered in GAC. This all works fine and good on pretty much every machine our software was deployed on before. But now we got 2 machines, seemingly identical to the ones we know work (they are cloned from the same image and stuffed with the same hardware, so pretty much the only difference is software settings, over which I went over and over, and they seem fine). Now the problem, the DLL in GAC takes a very long time to load. At least I believe this is the issue, what I can say definitively is that instantiating a single class from that DLL is the slow part. Once it is loaded, thing fly as they always have. But while on known-good machines the DLL loads so fast that a timestamp in the log doesn't even change, on these 2 machines it take over 1min to load. Knowns: I have no access to the source, so I can't debug through the DLL. Our app is the only one that uses it (so shouldn't be simultaneous access issues). There is only one version of this DLL in existance, so it shouldn't be a matter of version conflict. The GAC reference is being used (if I uninstall the DLL from GAC, an exception will be thrown about the missing GAC reference). Could someone with a greater skill in debug-fu suggest what I can do to track down the root cause of this issue?

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  • Is GAE Really GZipping My Content? Slow Response Times with GAE as CDN

    - by viatropos
    I am testing out Google App Engine as a free Content Delivery Network and it feels like it's taking a long time to serve up my content. Why does this gae page take a say a half a second to download, while your typical stack overflow page downloads much faster even with a ton more content? What am I missing here? All I have done is create an app and uploaded an image according to that tutorial, but content is being served very slowly it seems. Any suggestions? (Not considering Amazon or other CDNs right now, just looking for help with GAE). Note: I am using Safari when I visit those links, maybe safari is causing problems?

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  • How to 'insert if not exists' in MySQL?

    - by warren
    I started by googling, and found this article which talks about mutex tables. I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)? Does a unique constraint on a field guarantee the insert will fail if it's already there? It seems that with merely a constraint, when I issue the insert via php, the script croaks.

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  • Are Conditional subquery

    - by Tobias Schulte
    I have a table foo and a table bar, where each foo might have a bar (and a bar might belong to multiple foos). Now I need to select all foos with a bar. My sql looks like this SELECT * FROM foo f WHERE [...] AND ($param IS NULL OR (SELECT ((COUNT(*))>0) FROM bar b WHERE f.bar = b.id)) with $param being replaced at runtime. The question is: Will the subquery be executed even if param is null, or will the dbms optimize the subquery out?

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  • Approach for altering Primary Key from GUID to BigInt in SQL Server related tables

    - by Tom
    I have two tables with 10-20 million rows that have GUID primary keys and at leat 12 tables related via foreign key. The base tables have 10-20 indexes each. We are moving from GUID to BigInt primary keys. I'm wondering if anyone has any suggestions on an approach. Right now this is the approach I'm pondering: Drop all indexes and fkeys on all the tables involved. Add 'NewPrimaryKey' column to each table Make the key identity on the two base tables Script the data change "update table x, set NewPrimaryKey = y where OldPrimaryKey = z Rename the original primarykey to 'oldprimarykey' Rename the 'NewPrimaryKey' column 'PrimaryKey' Script back all the indexes and fkeys Does this seem like a good approach? Does anyone know of a tool or script that would help with this? TD: Edited per additional information. See this blog post that addresses an approach when the GUID is the Primary: http://www.sqlmag.com/blogs/sql-server-questions-answered/sql-server-questions-answered/tabid/1977/entryid/12749/Default.aspx

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  • Are closures in javascript recompiled

    - by Discodancer
    Let's say we have this code (forget about prototypes for a moment): function A(){ var foo = 1; this.method = function(){ return foo; } } var a = new A(); is the inner function recompiled each time the function A is run? Or is it better (and why) to do it like this: function method = function(){ return this.foo; } function A(){ this.foo = 1; this.method = method; } var a = new A(); Or are the javascript engines smart enough not to create a new 'method' function every time? Specifically Google's v8 and node.js. Also, any general recommendations on when to use which technique are welcome. In my specific example, it really suits me to use the first example, but I know thath the outer function will be instantiated many times.

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