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  • vector<vector<largeObject>> vs. vector<vector<largeObject>*> in c++

    - by Leif Andersen
    Obviously it will vary depending on the compiler you use, but I'm curious as to the performance issues when doing vector<vector<largeObject>> vs. vector<vector<largeObject>*>, especially in c++. In specific: let's say that you have the outer vector full, and you want to start inserting elements into first inner vector. How will that be stored in memory if the outer vector is just storing pointers, as apposed to storing the whole inner vector. Will the whole outer vector have to be moved to gain more space, or will the inner vector be moved (assuming that space wasn't pre-allocated), causing problems with the outer vector? Thank you

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  • assistance with classifying tests

    - by amateur
    I have a .net c# library that I have created that I am currently creating some unit tests for. I am at present writing unit tests for a cache provider class that I have created. Being new to writing unit tests I have 2 questions These being: My cache provider class is the abstraction layer to my distributed cache - AppFabric. So to test aspects of my cache provider class such as adding to appfabric cache, removing from cache etc involves communicating with appfabric. Therefore the tests to test for such, are they still categorised as unit tests or integration tests? The above methods I am testing due to interacting with appfabric, I would like to time such methods. If they take longer than a specified benchmark, the tests have failed. Again I ask the question, can this performance benchmark test be classifed as a unit test? The way I have my tests set up I want to include all unit tests together, integration tests together etc, therefore I ask these questions that I would appreciate input on.

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  • Mongodb using db.help() on a particular db command

    - by user1325696
    When I type db.help() It returns DB methods: db.addUser(username, password[, readOnly=false]) db.auth(username, password) ... ... db.printShardingStatus() ... ... db.fsyncLock() flush data to disk and lock server for backups db.fsyncUnock() unlocks server following a db.fsyncLock() I'd like to find out how to get more detailed help for the particular command. The problem was with the printShardingStatus as it returned "too many chunks to print, use verbose if you want to print" mongos> db.printShardingStatus() --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3 } shards: { "_id" : "shard0000", "host" : "localhost:10001" } { "_id" : "shard0001", "host" : "localhost:10002" } databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "dbTest", "partitioned" : true, "primary" : "shard0000" } dbTest.things chunks: shard0001 12 shard0000 19 too many chunks to print, use verbose if you want to for ce print I found that for that particular command I can specify boolean parameter db.printShardingStatus(true) which wasn't shown using db.help().

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  • What messaging technologies in windows-ce for guaranteed msg delivery?

    - by Aidanapword
    We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (I have not found any RabbitMQ clients for CE, by example) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too.

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  • Best way to provide software settings?

    - by claws
    I'm using C# .NET. In my software I'm providing settings dialog through which user can set the application settings which I want to save to a file. Requirements (typical): Every class I defined uses some part of these settings. So, these should be global to all classes. These should be loaded while software is started. When ever user changes settings and clicks 'save'/'apply'. Current settings should change. I am wondering what is the best way to do this? Also, what is the best way to save these settings to disk? I mean should I create a Settings class object and serializing it to 'settings.dat' or provide an structured file like XML/JSON

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  • MSSQL choosing row (from group) with max value

    - by sriehl
    I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year.

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  • Reading files from an embedded ZIP archive

    - by aix
    I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length. Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file. For performance reasons, I cannot copy the ZIP achive into a separate file before opening it. edit: Just to be clear, I do have random access to the file.

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  • How can I dynamically inject code into event handlers in Delphi?

    - by mjustin
    For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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  • Intercept windows open file

    - by HyLian
    Hello, I'm trying to make a small program that could intercept the open process of a file. The purpose is when an user double-click on a file in a given folder, windows would inform to the software, then it process that petition and return windows the data of the file. Maybe there would be another solution like monitoring Open messages and force Windows to wait while the program prepare the contents of the file. One application of this concept, could be to manage desencryption of a file in a transparent way to the user. In this context, the encrypted file would be on the disk and when the user open it ( with double-click on it or with some application such as notepad ), the background process would intercept that open event, desencrypt the file and give the contents of that file to the asking application. It's a little bit strange concept, it could be like "Man In The Middle" network concept, but with files instead of network packets. Thanks for reading.

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  • MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

    - by Cory House
    MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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  • MySQL locking problem

    - by teehoo
    I have a simple setup of a set of writers and a set of readers working with a MySQL ISAM table. The writers are only inserting rows while the readers are only checking for new rows. OK, so I know that I don't need a lock in this situation, since I'm not modifying existing rows. However my Writers are accessing one more table that does need a lock. I piece of information seems irrelevant except for the following limitation stated in the MySQL documentation: A session that requires locks must acquire all the locks that it needs in a single LOCK TABLES statement. While the locks thus obtained are held, the session can access only the locked tables. For example, in the following sequence of statements, an error occurs for the attempt to access t2 because it was not locked in the LOCK TABLES statement: So to access the table I want to insert rows into, I NEED to lock it, which is causing me performance problems. Any suggestions of how to get around this?

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  • Getting latest Subsonic builds

    - by Alex Yakunin
    I need the latest Subsonic build or build it by my own. Subsonic project web site shows the latest available version is Subsonic v3.0.0.3 released at July 15, 2009. Questions: Are there any later builds - e.g. maintained by community members? If so, how can I get the latest one? In worst case I'm ready to get the latest source code and try to build it by my own. Are there any instructions for this? Please note, that I'm not interested in almost 1 year old builds - I need a build based on the latest code for tests (LINQ, performance), ideally - compiled for .NET 4.0.

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  • Measuring daemon CPU utilization over a portion of it's wall clock run time

    - by WhirlWind
    I am dealing with a network-related daemon: it takes data in, processes it, and spits it out. I would like to increase the performance of this daemon by profiling it and reducing it's CPU utilization. I can do this easily on Linux with gprof. However, I would also like to use something like "time" to measure it's total CPU utilization over a period of time. If possible, I would like to time it over a period that is less than its total run time: thus, I would like to start the daemon, wait awhile, generate CPU statistics, stop generating them, then stop the daemon at some later time. The "time" command would work well for me, but it seems to require that I start and stop the daemon as a child of time. Is there a way to measure CPU utilization for only a portion of the daemon's wall clock time?

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  • What is the best Java numerical method package?

    - by Bob Cross
    I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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  • Semantic stuff (RDF, OWL) on mobile phones - is it possible?

    - by Brian Schimmel
    I'm thinking about using semantic (web) technogies like RDF and OWL in an application on mobile devices. Currently I'm targeting android, but I'd also be interested in the possibilities on the iPhone and on J2ME. I would like to use a lib instead of implementing everything from scratch. I know that there are some libraries and frameworks like Jena, Redland, Protégé but they don't state on which platforms they are known to work. Having a dynamic object model and parsing from and to XML are must-haves for me. I'd also like to use reasoning, but I've been told it was rather computing-intensive, so that's only a nice-to-have. For all platforms mentioned, the question can be interpreted as Is it possible in theory (especially for J2ME I'm not sure) Are there libs that are known to work on those platforms? Is the performance on a mobile platform good enough for real world usage?

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  • Good reasons why to not use XIB files?

    - by mystify
    Are there any good reasons why I should not use XIB / NIB files with an highly customized UI and extensive animations and super low memory footprint needs? As a beginner I started with XIB. Then I figured out I couldn't do just about everything in them. It started to get really hard to customize things the way I wanted them to be. So at the end, I threw all my XIBs away and did it all programmatically. So when someone asks me if XIB is good, I generally say: Yeah, if you want to make crappy boring interfaces and don't care too much about performance, go ahead. But what else could be a reason not to use XIB? Am I the only iPhone developer who prefers doing everything programmatically for this reasons?

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  • Asp .Net MVC Viewmodel should be class or struct?

    - by Jonas Everest
    Hey guys, I have just been thinking about the concept of view model object we create in asp.net MVC. Our purpose is to instantiate it and pass it from controller to view and view read it and display the data. Those view model are usually instantiated through constructor. We won't need to initialize the members, we may not need to redefine/override parameterless constructor and we don't need inheritance feature there. So, why don't we use struct type for our view model instead of class. It will enhance the performance.

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  • Play Shoutcast MP3 radio stream with Python?

    - by Zachary Brown
    I have managed to create an online radio station using Shoutcast and Sam Broadcaster. Now, I am wanting to build my own player for that radio station. I am not sure where to begin, I have googled, but no luck. I am using Python 2.6 on Microsoft Windows. I have managed to capture the stream and save it as an MP# on the hard disk, just not sure what to do with it next. I tried playback of the file, but it always pulls up errors. This is the code I have so far: import urllib target = open("broadcast.mp3") conn = urllib.urlopen("http://78.159.104.175:80") while True: target.write(con.read(5200)) Any help would be greatly appreciated!

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  • How to reliably measure available memory in Linux?

    - by Alex B
    Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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  • Endianness manipulation - is there a C library for this?

    - by Malvineous
    Hi all, With the sort of programs I write (working with raw file data) I often need functions to convert between big and little endian. Usually I write these myself (which is covered by many other posts here) but I'm not that keen on doing this for a number of reasons - the main one being lack of testing. I don't really want to spend ages testing my code in a big endian emulator, and often just omit the code for big endian machines altogether. I also would rather make use of faster functions provided by various compilers, while still keeping my programs cross-platform. The only things I can find are socket calls like htons() but they require different #include files on each platform, and some GPL code like this, however that particular file, while comprehensive, seems to miss out on some of the high performance functions provided by some compilers. So, does anyone know of a library (ideally just a .h file) that is well tested and provides a standard set of functions for dealing with endianness across many compilers and platforms?

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  • Append in Dom taking more time in IE than Firefox or any other browser.

    - by user307635
    Hi , I m working on .net framework 3.0 visual studio 08 and Testing it in IE8 and other browsers. Whenever I m inserting new elements in DOM (ex. 300 divs at one time) than I m getting the performance very slow in IE . Why?. If its a javascript debugging which is taking time or what else. Is it really true that IE Dom Append takes much time than any other browser. Please help me , I m stuck badly.

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  • input of while loop to come from output of `command`

    - by Felipe Alvarez
    #I used to have this, but I don't want to write to the disk # pcap="somefile.pcap" tcpdump -n -r $pcap > all.txt while read line; do ARRAY[$c]="$line" c=$((c+1)) done < all.txt The following fails to work. # I would prefer something like... # pcap="somefile.pcap" while read line; do ARRAY[$c]="$line" c=$((c+1)) done < $( tcpdump -n -r "$pcap" ) Too few results on Google (doesn't understand what I want to find :( ). I'd like to keep it Bourne-compatible (/bin/sh), but it doesn't have to be.

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  • Is is better to store serialized data or raw html in mysql?

    - by Yegor
    I de-normalized my database, since the application was crawling otherwise, and Im storing a list of categories for each item in the DB as a raw html version, and simply echoing it out in my design. Each category is actually a link, which is include a tag. Naturally, this is abit of a pain, especially if I want to change the look of how the category links are displayed, since I gotta update all the old cached entries. What if I were to store this data as a serialized array instead, and simply unserialize it, and then apply formatting to it in php. Would there be a significant performance decrease over simply echoing out the raw html?

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  • What is a .NET managed module?

    - by Abhijeet Patel
    I know it's a Windows PE32, but I also know that the unit of deployment in .NET is an assembly which in turn has a manifest and can be made up of multiple managed modules. My questions are : 1) How would you create multiple managed modules when building a project such as a class lib or a console app etc. 2) Is there a way to specify this to the compiler(via the project properties for example) to partition your source code files into multiple managed modules. If so what is the benefit of doing so? 3)Can managed modules span assemblies? 4)Are separate file created on disk when the source code is compiled or are these created in memory and directly embedded in an assembly?

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  • Maximizing the number of threads to fully utilize all available resources without hindering overall

    - by Matt
    Let's say I have to generate a bunch of result files, and I want to make it as fast as possible. Each result file is generated independently of any other result file; in fact, one could say that each result file is agnostic to every other result file. The resources used to generate each result file is also unique to each. How can I dynamically decide the optimal number of threads to run simultaneously in order to minimize the overall run time? Is my only option to write my own thread manager that watches performance counters and adjust accordingly or does there exists some solid classes that already accomplish this?

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