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  • pyopengl: Could it replace c++ ?

    - by Tom
    Hi everyone. I'm starting a computer graphics course, and I have to choose a language. Choices are between C++ and Python. I have no problem with C++, python is a work in progress. So i was thinking to go down the python road, using pyopengl for graphics part. I have heard though, that performance is an issue. Is python / pyopengl mature enough to challenge C++ on performance? I realize its a long shot, but I'd like to hear your thoughts, experiences on uses of pyopengl. Thanks in advance.

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  • Popularity Algorithm - SQL / Django

    - by RadiantHex
    Hi folks, I've been looking into popularity algorithms used on sites such as Reddit, Digg and even Stackoverflow. Reddit algorithm: t = (time of entry post) - (Dec 8, 2005) x = upvotes - downvotes y = {1 if x > 0, 0 if x = 0, -1 if x < 0) z = {1 if x < 0, otherwise x} log(z) + (y * t)/45000 I have always performed simple ordering within SQL, I'm wondering how I should deal with such ordering. Should it be used to define a table, or could I build an SQL with the ordering within the formula (without hindering performance)? I am also wondering, if it is possible to use multiple ordering algorithms in different occasions, without incurring into performance problems. I'm using Django and PostgreSQL. Help would be much appreciated! ^^

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  • Insert rownumber repeatedly in records in t-sql.

    - by jeff
    Hi, I want to insert a row number in a records like counting rows in a specific number of range. example output: RowNumber ID Name 1 20 a 2 21 b 3 22 c 1 23 d 2 24 e 3 25 f 1 26 g 2 27 h 3 28 i 1 29 j 2 30 k I rather to try using the rownumber() over (partition by order by column name) but my real records are not containing columns that will count into 1-3 rownumber. I already try to loop each of record to insert a row count 1-3 but this loop affects the performance of the query. The query will use for the RDL report, that is why as much as possible the performance of the query must be good. any suggestions are welcome. Thanks

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  • Assert parameters in a table-valued UDF

    - by Clay Lenhart
    Is there a way to create "asserts" on the parameters of a table-valued UDF. I'd like to use a table-valued UDF for performance reasons, however I know that certain parameter combinations (like start and end dates that are more than a month apart) will cause performance issues on the server for all users. End users query the database via Excel using UDFs. UDFs (and table-valued UDFs in particular) are useful when the data is too large for Excel. Users write simple SQL queries that categorizes the data into groups to reduce the number of rows. For example, the user may be interested in weekly aggregates rather than hourly ones. Users write a group by SELECT statement to reduce the rows by 24x7=168 times. I know I can write RAISERROR statements in multistatement UDFs, but table-valued UDFs are integrated in the query optimizer so these queries are more efficient with table-valued UDFs. So, can I define assertions on the parameters passed to a table-valued UDF?

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  • Is it too early to start designing for Task Parallel Library?

    - by Joe Erickson
    I have been following the development of the .NET Task Parallel Library (TPL) with great interest since Microsoft first announced it. There is no doubt in my mind that we will eventually take advantage of TPL. What I am questioning is whether it makes sense to start taking advantage of TPL when Visual Studio 2010 and .NET 4.0 are released, or whether it makes sense to wait a while longer. Why Start Now? The .NET 4.0 Task Parallel Library appears to be well designed and some relatively simple tests demonstrate that it works well on today's multi-core CPUs. I have been very interested in the potential advantages of using multiple lightweight threads to speed up our software since buying my first quad processor Dell Poweredge 6400 about seven years ago. Experiments at that time indicated that it was not worth the effort, which I attributed largely to the overhead of moving data between each CPU's cache (there was no shared cache back then) and RAM. Competitive advantage - some of our customers can never get enough performance and there is no doubt that we can build a faster product using TPL today. It sounds fun. Yes, I realize that some developers would rather poke themselves in the eye with a sharp stick, but we really enjoy maximizing performance. Why Wait? Are today's Intel Nehalem CPUs representative of where we are going as multi-core support matures? You can purchase a Nehalem CPU with 4 cores which share a single level 3 cache today, and most likely a 6 core CPU sharing a single level 3 cache by the time Visual Studio 2010 / .NET 4.0 are released. Obviously, the number of cores will go up over time, but what about the architecture? As the number of cores goes up, will they still share a cache? One issue with Nehalem is the fact that, even though there is a very fast interconnect between the cores, they have non-uniform memory access (NUMA) which can lead to lower performance and less predictable results. Will future multi-core architectures be able to do away with NUMA? Similarly, will the .NET Task Parallel Library change as it matures, requiring modifications to code to fully take advantage of it? Limitations Our core engine is 100% C# and has to run without full trust, so we are limited to using .NET APIs.

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  • SQL Query to delete oldest rows over a certain row count?

    - by Casey
    I have a table that contains log entries for a program I'm writing. I'm looking for ideas on an SQL query (I'm using SQL Server Express 2005) that will keep the newest X number of records, and delete the rest. I have a datetime column that is a timestamp for the log entry. I figure something like the following would work, but I'm not sure of the performance with the IN clause for larger numbers of records. Performance isn't critical, but I might as well do the best I can the first time. DELETE FROM MyTable WHERE PrimaryKey NOT IN (SELECT TOP 10,000 PrimaryKey FROM MyTable ORDER BY TimeStamp DESC)

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  • Weaknesses of Hibernate

    - by Sinuhe
    I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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  • Best way to encrypt certain fiels in SQL Server 2008?

    - by Josh
    I'm writing a .net web app that will read and write information to a SQL 2008 backend database. Some of this information will be highly confidential in nature so I want to encrypt certain data elements. I dont want to use TDE or any full-database encryption for performance reasons. My main concern is protecting this sensitive data as a last resort against a SQL injection or even a database server compromise. My question is what is the best way to do this to preserve performance? Is it faster to use the SQL2008 encryption functions such as EncryptByKey, or would it be faster to encrypt and decrypt the data in the .NET web app itself using a symmetric key stored in the secure web.config and store the encrypted values in the DB?

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  • fastest in-memory cache for XslCompiledTransform

    - by rudnev
    I have a set of xslt stylesheet files. I need to produce the fastest performance of XslConpiledTransform, so i want to make in-memory representation of these stylesheets. I can load them to in-memory collection as IXpathNavigable on application start, and then load each IXPAthNavigable into singleton XslCompiledTransform on each request. But this works only for styleshhets without xsl:import or xsl:include. (Xsl:import is only for files). also i can load into cache many instances of XSLCompiledTransform for each template. Is it reasonable? Are there other ways? What is the best? what are another tips for improving performance MS Xslt processor?

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • ASMX Still slow after 'Generate serialization assembly'

    - by Buzzer
    This question is related to: http://stackoverflow.com/questions/784918/asmx-web-service-slow-first-request. I inherited a proxy to a legacy ASMX Service. Basically as the post above states, the first call performance is literally 10 times slower than the subsequent calls. I went ahead and turned on ‘Generate serialization assembly' on the project that contains the proxy. The 'serializers' assembly is actually generated. However, I haven't seen any performance increase at all. Do I need to do anything else other than make sure the 'serializers' assembly is in the client's bin directory? Do I have to 'link' the proxy to the 'serializers' assembly during proxy generation (wsdl.exe)? I guess I'm stuck at this point. J Saunders where u at? :)

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  • Avoid implicit conversion from date to timestamp for selects with Oracle using Hibernate

    - by sapporo
    I'm using Hibernate 3.2.7.GA criteria queries to select rows from an Oracle Enterprise Edition 10.2.0.4.0 database, filtering by a timestamp field. The field in question is of type java.util.Date in Java, and DATE in Oracle. It turns out that the field gets mapped to java.sql.Timestamp, and Oracle converts all rows to TIMESTAMP before comparing to the passed in value, bypassing the index and thereby ruining performance. One solution would be to use Hibernate's sqlRestriction() along with Oracle's TO_DATE function. That would fix performance, but requires rewriting the application code (lots of queries). So is there a more elegant solution? Since Hibernate already does type mapping, could it be configured to do the right thing? Update: The problem occurs in a variety of configurations, but here's one specific example: Oracle Enterprise Edition 10.2.0.4.0 Oracle JDBC Driver 11.1.0.7.0 Hibernate 3.2.7.GA Hibernate's Oracle10gDialect Java 1.6.0_16

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  • What's wrong with my logic here?

    - by stu
    In java they say don't concatenate Strings, instead you should make a stringbuffer and keep adding to that and then when you're all done, use toString() to get a String object out of it. Here's what I don't get. They say do this for performance reasons, because concatenating strings makes lots of temporary objects. But if the goal was performance, then you'd use a language like C/C++ or assembly. The argument for using java is that it is a lot cheaper to buy a faster processor than it is to pay a senior programmer to write fast efficient code. So on the one hand, you're supposed let the hardware take care of the inefficiencies, but on the other hand, you're supposed to use stringbuffers to make java more efficient. While I see that you can do both, use java and stringbuffers, my question is where is the flaw in the logic that you either use a faster chip or you spent extra time writing more efficient software.

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  • How to set that compiler flag?

    - by mystify
    Shark told me this: This instruction is the start of a loop that is not aligned to a 16-byte address boundary. For optimal performance, you should align the start of a hot loop using a compiler directive. With gcc 3.3 or later, use the -falign-loops=16 compiler flag. for (int i=0; i < 4; i++) { // line with the info //...code } How would I set that flag, and does it really improve performance?

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  • Managing EntityConnection lifetime

    - by kervin
    There have been many question on managing EntityContext lifetime, e.g. http://stackoverflow.com/questions/813457/instantiating-a-context-in-linq-to-entities I've come to the conclusion that the entity context should be considered a unit-of-work and therefore not reused. Great. But while doing some research for speeding up my database access, I ran into this blog post... Improving Entity Framework Performance The post argues that EFs poor performance compared to other frameworks is often due to the EntityConnection object being created each time a new EntityContext object is needed. To test this I manually created a static EntityConnection in Global.asax.cs Application_Start(). I then converted all my context using statements to using( MyObjContext currContext = new MyObjeContext(globalStaticEFConnection) { .... } This seems to have sped things up a bit without any errors so far as far as I can tell. But is this safe? Does using a applicationwide static EntityConnection introduce race conditions? Best regards, Kervin

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  • Virtual Function Implementation

    - by Gokul
    Hi, I have kept hearing this statement. Switch..Case is Evil for code maintenance, but it provides better performance(since compiler can inline stuffs etc..). Virtual functions are very good for code maintenance, but they incur a performance penalty of two pointer indirections. Say i have a base class with 2 subclasses(X and Y) and one virtual function, so there will be two virtual tables. The object has a pointer, based on which it will choose a virtual table. So for the compiler, it is more like switch( object's function ptr ) { case 0x....: X->call(); break; case 0x....: Y->call(); }; So why should virtual function cost more, if it can get implemented this way, as the compiler can do the same in-lining and other stuff here. Or explain me, why is it decided not to implement the virtual function execution in this way? Thanks, Gokul.

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  • What are all the disadvantages of using files as a means of communicating between two processes?

    - by Manny
    I have legacy code which I need to improve for performance reasons. My application comprises of two executables that need to exchange certain information. In the legacy code, one exe writes to a file ( the file name is passed as an argument to exe) and the second executable first checks if such a file exists; if does not exist checks again and when it finds it, then goes on to read the contents of the file. This way information in transferred between the two executables. The way the code is structured, the second executable is successful on the first try itself. Now I have to clean this code up and was wondering what are the disadvantages of using files as a means of communication rather than some inter-process communication like pipes.Is opening and reading a file more expensive than pipes? Are there any other disadvantages? And how significant do you think would be the performance degradation. The legacy code is run on both windows and linux.

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  • Refactor/rewrite code or continue?

    - by Dan
    I just completed a complex piece of code. It works to spec, it meets performance requirements etc etc but I feel a bit anxious about it and am considering rewriting and/or refactoring it. Should I do this (spending time that could otherwise be spent on features that users will actually notice)? The reasons I feel anxious about the code are: The class hierarchy is complex and not obvious Some classes don't have a well defined purpose (they do a number of unrelated things) Some classes use others internals (they're declared as friend classes) to bypass the layers of abstraction for performance, but I feel they break encapsulation by doing this Some classes leak implementation details (eg, I changed a map to a hash map earlier and found myself having to modify code in other source files to make the change work) My memory management/pooling system is kinda clunky and less-than transparent They look like excellent reasons to refactor and clean code, aiding future maintenance and extension, but could be quite time consuming. Also, I'll never be perfectly happy with any code I write anyway... So, what does stackoverflow think? Clean code or work on features?

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  • How to figure the read/write ratio in Sql Server?

    - by Bill Paetzke
    How can I query the read/write ratio in Sql Server 2005? Are there any caveats I should be aware of? Perhaps it can be found in a DMV query, a standard report, a custom report (i.e the Performance Dashboard), or examining a Sql Profiler trace. I'm not sure exactly. Why do I care? I'm taking time to improve the performance of my web app's data layer. It deals with millions of records and thousands of users. One of the points I'm examining is database concurrency. Sql Server uses pessimistic concurrency by default--good for a write-heavy app. If my app is read-heavy, I might switch it to optimistic concurrency (isolation level: read uncommitted snapshot) like Jeff Atwood did with StackOverflow.

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  • Make a compiled binary run at native speed flawlessly without recompiling from source on a another system?

    - by unknownthreat
    I know that many people, at a first glance of the question, may immediately yell out "Java", but no, I know Java's qualities. Allow me to elaborate my question first. Normally, when we want our program to run at a native speed on a system, whether it be Windows, Mac OS X, or Linux, we need to compile from source codes. If you want to run a program of another system in your system, you need to use a virtual machine or an emulator. While these tools allow you to use the program you need on the non-native OS, they sometimes have problems of performance and glitches. We also have a newer compiler called "JIT Compiler", where the compiler will parse the bytecode program to native machine language before execution. The performance may increase to a very good extent with JIT Compiler, but the performance is still not the same as running it on a native system. Another program on Linux, WINE, is also a good tool for running Windows program on Linux system. I have tried running Team Fortress 2 on it, and tried experiment with some settings. I got ~40 fps on Windows at its mid-high setting on 1280 x 1024. On Linux, I need to turn everything low at 1280 x 1024 to get ~40 fps. There are 2 notable things though: Polygon model settings do not seem to affect framerate whether I set it low or high. When there are post-processing effects or some special effects that require manipulation of drawn pixels of the current frame, the framerate will drop to 10-20 fps. From this point, I can see that normal polygon rendering is just fine, but when it comes to newer rendering methods that requires graphic card to the job, it slows down to a crawl. Anyway, this question is rather theoretical. Is there anything we can do at all? I see that WINE can run STEAM and Team Fortress 2. Although there are flaws, they can run at lower setting. Or perhaps, I should also ask, "is it possible to translate one whole program on a system to another system without recompiling from source and get native speed?" I see that we also have AOT Compiler, is it possible to use it for something like this? Or there are so many constraints (such as DirectX call or differences in software architecture) that make it impossible to have a flawless and not native to the system program that runs at native speed?

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  • Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?

    - by BritishDeveloper
    How would you rate each of them in terms of: Performance Speed of development Neat, intuitive, maintainable code Flexibility Overall I like my SQL and so have always been a die-hard fan of ADO.NET and stored procedures but I recently had a play with Linq to SQL and was blown away by how quickly I was writing out my DataAccess layer and have decided to spend some time really understanding either Linq to SQL or EF... or neither? I just want to check, that there isn't a great flaw in any of these technologies that would render my research time useless. E.g. performance is terrible, it's cool for simple apps but can only take you so far

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  • [SWT/RCP] Alpha blending is slow on linux

    - by elgcom
    we are developing an SWT/RCP(Eclipse 3.5) application on both Windows and Linux (on identical hardware). The application is a GIS app which shows several layered maps(PNG images) rendered with alpha blending. org.eclipse.draw2d.Graphics.setAlpha(...); org.eclipse.draw2d.Graphics.drawImage(...); On Windows the performance is pretty good, but on Linux it is very poor. is that a Linux(GTK/KDE) problem? or is there any workaround to improve the performance on Linux?

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