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• Understanding OpenGL Matrices

  - by Omega

  I'm starting to learn about 3D rendering and I've been making good progress. I've picked up a lot regarding matrices and the general operations that can be performed on them. One thing I'm still not quite following is OpenGL's use of matrices. I see this (and things like it) quite a lot: x y z n ------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 So my best understanding, is that it is a normalized (no magnitude) 4 dimensional, column-major matrix. Also that this matrix in particular is called the "identity matrix". Some questions: What is the "nth" dimension? How and when are these applied? My biggest confusion arises from how OpenGL makes use of this kind of data.

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• How much more complex is it to draw simple curves, lines and circles in OpenGL ES rather than in Qua

  - by mystify

  Is OpenGL ES really so much faster? Why? And is it really so horrible complicated to draw such simple things in OpenGL ES compared to drawing these in Quartz 2D? For example, I have a UIView subclass with -drawRect: implemented, where I draw some lines, curves and circles. Just simple paths, with some shadow. What would I do in OpenGL ES? Isn't there this nice EAGLView layer thing? One thing that comes to mind is how do touch events go into OpenGL ES? Maybe that's the complex thing about it? Are there tutorials on basic drawing operations in OpenGL ES?

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• A compiler for automata theory

  - by saadtaame

  I'm designing a programming language for automata theory. My goal is to allow programmers to use machines (DFA, NFA, etc...) as units in expressions. I'm confused whether the language should be compiled, interpreted, or jit-compiled! My intuition is that compilation is a good choice, for some operations might take too much time (converting NFA's to equivalent DFA's can be expensive). Translating to x86 seems good. There is one issue however: I want the user to be able to plot machines. Any ideas?

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• Cross-reference between delphi records

  - by Paul-Jan

  Let's say I have a record TQuaternion and a record TVector. Quaternions have some methods with TVector parameters. On the other hand, TVector supports some operations that have TQuaternion parameters. Knowing that Delphi (Win32) does not allow for forward record declarations, how do I solve this elegantly? Using classes is not really an option here, because I really want to use operator overloading for this rare case where it actually makes good sense. For now I simply moved these particular methods out of the records and into separate functions, the good old-fashioned way. Better suggestions are most welcome.

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• How can I parse a C header file with Perl?

  - by Alphaneo

  Hi, I have a header file in which there is a large struct. I need to read this structure using some program and make some operations on each member of the structure and write them back. For example I have some structure like const BYTE Some_Idx[] = { 4,7,10,15,17,19,24,29, 31,32,35,45,49,51,52,54, 55,58,60,64,65,66,67,69, 70,72,76,77,81,82,83,85, 88,93,94,95,97,99,102,103, 105,106,113,115,122,124,125,126, 129,131,137,139,140,149,151,152, 153,155,158,159,160,163,165,169, 174,175,181,182,183,189,190,193, 197,201,204,206,208,210,211,212, 213,214,215,217,218,219,220,223, 225,228,230,234,236,237,240,241, 242,247,249}; Now, I need to read this and apply some operation on each of the member variable and create a new structure with different order, something like: const BYTE Some_Idx_Mod_mul_2[] = { 8,14,20, ... ... 484,494,498}; Is there any Perl library already available for this? If not Perl, something else like Python is also OK. Can somebody please help!!!

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• C# Crypto API examples

  - by Gearoid Murphy

  Hello, I'm looking for examples + information on how to extract certificate information from the windows certificate store and perform operations like verifying signatures using the retrieved certificates. The API documentation for C# in this regard is quite poor, with many of the entries in msdn marked with "This language is not supported, or no code example is available.", I'm sorry I can't be more specific, I haven't done any programming using cryptographic api's. The particular certificate will be provided via a USB token. Any help or pointers would be much appreciated, thanks.

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• cached schwartzian transform

  - by davidk01

  I'm going through "Intermediate Perl" and it's pretty cool. I just finished the section on "The Schwartzian Transform" and after it sunk in I started to wonder why the transform doesn't use a cache. In lists that have several repeated values the transform recomputes the value for each one so I thought why not use a hash to cache results. Here' some code: # a place to keep our results my %cache; # the transformation we are interested in sub foo { # expensive operations } # some data my @unsorted_list = ....; # sorting with the help of the cache my @sorted_list = sort { ($cache{$a} or $cache{$a} = &foo($a)) <=> ($cache{$b} or $cache{$b} = &foo($b)) } @unsorted_list; Am I missing something? Why isn't the cached version of the Schwartzian transform listed in books and in general just better circulated because on first glance I think the cached version should be more efficient?

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• What is the difference between File and FileInfo in C# ?

  - by Lilitu88

  I've been reading that the static methods of the File Class are better used to perform small and few tasks on a file like checking to see if it exists and that we should use an instance of the FileInfo Class if we are going to perform many operations on a specific file. I understand this and can simply use it that way blindly but I would like to know why is there a difference ? What is it about the way they work that make them suitable for different situations ? What is the point of having this 2 different classes that seem do the same in different ways ? It would be helpful if someone could answer at least one of this questions.

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• Clustered index dilemma - ID or sort?

  - by richardtallent

  I have a table with two very important fields: id INT identity(1,1) PRIMARY KEY identifiersortcode VARCHAR(900) My app always sorts and pages search results in the UI based on identifiersortcode, but all table joins (and they are legion) are on the id field. (Aside: yes, the sort code really is that long. There's a strong BL reason.) Also, due to O/RM use, most SELECT statements are going to pull almost every column. Currently, the clustered index is on id, but I'm wondering if the TOP / ORDER BY portion of most queries would make identifiersortcode a more attractive option as the clustered key, even considering all of the table joins going on. Inserts on the table and changes to the identifiersortcode are limited enough that changing my clustered index would be a problem for insert/update operations. Trying to make the sort code's non-clustered index a covering index (using INCLUDE) is not a good option. There are a number of large columns, and some of them have a lot of update activity.

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• Is it possible to call a user-space callback function from kernel space in Linux (ioctl)?

  - by Makis

  Is it possible to expand the ioctl interface in Linux so that the user-space application can send a pointer to a function to the kernel space driver? I'm in particular thinking of ways to handle the stream in user-controllable way but doing it in the kernel. Those operations could be attached to the kernel module but this would make development a lot easier as I wouldn't need to mess with the kernel during development. More specifically, this would be the process: Data is read by the driver to a buffer. Data is handled by these user-defined functions in place. Some more handling is done, possibly with some HW blocks. Data is used by a user-space application.

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• custom tag 'cannot be resolved to a type'

  - by lotus99t

  I have a custom tag, packaged into a library jar that is included in my web apps war file. I get the following error: An error occurred at line: 66 in the jsp file: /WEB-INF/jsp/portlet/portfolio/operations/operationsInfo.jsp org.apache.jsp.tag.meta.form.WidgetFactory_tag cannot be resolved to a type 63: <c:forEach var="fldCfg" items="${config.page.fields}" > 64: <tr> 65: <td><form:Label fld="${fldCfg}"/></td> 66: <td><form:WidgetFactory fld="${fldCfg}" decodesMap="${decodesMap}" command="${operationsInfoBean}" dateFormat="${preferredDateFormat}"/></td> 67: </tr> 68: </c:forEach> 69: </table> But it doesn't seem to complain about Label which is in the same taglib. I've confirmed that the jar is in the war and that the tag file is in the jar and the that the TLD (in META-INF) expressly defines 'WidgetFactory' Why am I getting this error?

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• If you are forced to use an Anemic domain model, where do you put your business logic and calculated

  - by Jess

  Our current O/RM tool does not really allow for rich domain models, so we are forced to utilize anemic (DTO) entities everywhere. This has worked fine, but I continue to struggle with where to put basic object-based business logic and calculated fields. Current layers: Presentation Service Repository Data/Entity Our repository layer has most of the basic fetch/validate/save logic, although the service layer does a lot of the more complex validation & saving (since save operations also do logging, checking of permissions, etc). The problem is where to put code like this: Decimal CalculateTotal(LineItemEntity li) { return li.Quantity * li.Price; } or Decimal CalculateOrderTotal(OrderEntity order) { Decimal orderTotal = 0; foreach (LineItemEntity li in order.LineItems) { orderTotal += CalculateTotal(li); } return orderTotal; } Any thoughts?

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• WeakReferences are not freed in embedded OS

  - by Carsten König

  I've got a strange behavior here: I get a massive memory leak in production running a WPF application that runs on a DLOG-Terminal (Windows Embedded Standard SP1) that behaves perfectly fine if I run it localy on a normal desktop (Win7 prof.) After many unsucessful attempts to find any problem I put one of those directly beside my monitor, installed the ANTs MemoryProfiler and did one hour test run simulating user operations on both the terminal and my development PC. Result is, that due to some strange reasons the embedded system piles up a huge amount of WeakReference and EffectiveValueEntry[] Objects. Here are are some pictures: Development (PC): And the terminal: Just look at the class list... Has anyone seen something like this before and are there known solutions to this? Where can I get help? (PS the terminals where installed with images prepared for .net4)

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• C++: A variation of priority queue

  - by Helltone

  I need some kind of priority queue to store pairs <key, value>. Values are unique, but keys aren't. I will be performing the following operations (most common first): random insertion; retrieving (and removing) all elements with the least key. random removal (by value); I can't use std::priority_queue because it only supports removing the head. For now, I'm using an unsorted std::list. Insertion is performed by just pushing new elements to the back (O(1)). Operation 2 sorts the list with std::sort (O(N*logN)), before performing the actual retrieval. Removal, however, is O(n), which is a bit expensive. Any idea of a better data structure?

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• Concise SSE and MMX instruction reference with latencies and throughput

  - by Joe

  I am trying to optimize some arithmetic by using the MMX and SSE instruction sets with inline assembly. However, I have been unable to find good references for the timings and usages of these enhanced instruction sets. Could you please help me find references that contain information about the throughput, latency, operands, and perhaps short descriptions of the instructions? So far, I have found: Intel Instruction References http://www.intel.com/Assets/PDF/manual/253666.pdf http://www.intel.com/Assets/PDF/manual/253667.pdf Intel Optimization Guide http://www.intel.com/Assets/PDF/manual/248966.pdf Timings of Integer Operations http://gmplib.org/~tege/x86-timing.pdf

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• How can i return IEnumarable data from function in GridView with Entity FrameWork?

  - by programmerist

  protected IEnumerable GetPersonalsData() { // List personel; using (FirmaEntities firmactx = new FirmaEntities()) { var personeldata = (from p in firmactx.Personals select new { p.ID, p.Name, p.SurName }); return personeldata.AsEnumerable(); } } i wan to send GetPersonelData() into GridView DataSource. Like That: gwPersonel.DataSource = GetPersonelData(); gwPersonel.DataBind(); it monitored to me on : gwPersonel.DataBind(); this error: "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection."

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• Is it bad programming style to have a single, maybe common, generic exception?

  - by m0s

  Hi, so in my program I have parts where I use try catch blocks like this try { DirectoryInfo dirInfo = new DirectoryInfo(someString); //I don't know if that directory exists //I don't know if that string is valid path string... it could be anything //Some operations here } catch(Exception iDontCareWhyItFailed) { //Didn't work? great... we will say: somethings wrong, try again/next one } Of course I probably could do checks to see if the string is valid path (regex), then I would check if directory exists, then I could catch various exceptions to see why my routine failed and give more info... But in my program it's not really necessary. Now I just really need to know if this is acceptable, and what would a pro say/think about that. Thanks a lot for attention.

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• Best solution for reporting database

  - by zzyzx

  Here is the situation: There is a transaction intensive database - used for both routine transactions and reports. I was wondering if I could isolate these two operations and 2 independent databases, so reports could run off of one database and all the transactions could occur in another one. This would improve performance for the OLTP SQL database. I have gone over a few options like, Mirroring, Log shipping, Replication, Snapshots, Clustering - but would like to discuss the best possible strategy for the desired result. Please advise the best solution to implement this strategy, or any other thoughts/suggestion you may have.

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• GIS: When and why to use ArcObjects over GDAL programming to work with ArcGIS rasters and vectors?

  - by anotherobject

  Im just starting off with GDAL + python to support operations that cannot be done with ArcGIS python geoprocessing scripting. Mainly I am doing spatial modeling/analysis/editing of raster and vector data. I am a bit confused when ArcObject development is required versus when GDAL can be used? Is there functionality of ArcObjects that GDAL does not do? Is the opposite true too? I am assuming that ArcObjects are more useful in developing online tools versus Desktop analysis and modeling where the difference is more to do with preference? In my case i prefer GDAL because of python support, which I believe ArcObjects lack. thanks!

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• Software Requirement Specifications for Web Applications

  - by illuminatedtiger

  Hi guys, I'm looking for some guidance/books to read when it comes to creating a software requirement specification for a web application. For inspiration I have read some spec documents for desktop based applications. The documents I have read capture a systems functional requirements in use cases which tend to be rather data oriented with use cases centered around the various CRUD operations the application is intended to perform. I like this structure however I'm finding it rather difficult to marry it to what my web application needs to do, mostly reading data as opposed to manipulating it. I've had a go at writing some use cases however they all tend to boil down to "Search for item", "Change view of search results" or "User selects facet to refine search results". This doesn't sound quite right to me and makes me wonder if I'm going about this the right way. Are there planning differences between web based and desktop based applications?

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• help with linq query

  - by Luis

  Hi, i am trying to get some data, but i dont know how can i do a if in linq, this is how i am trying to do from so in db.Operations where ((opType!= "0" ? so.Operation == int.Parse(opType) : false) && (idState!=0 ? so.State == idState : false) && (start != null ? so.StartDate == start : false) && (end !=null ? so.EndDate == end : false)) select so the optype is a Int, the idState is a Int, end is a datetime, start is a datime what i am trying to do is, if those aren't null they add to the query function, so i can get all data together

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• Iterating Oracle collections of objects with out exploding them

  - by Scott Bailey

  I'm using Oracle object data types to represent a timespan or period. And I've got to do a bunch of operations that involve working with collections of periods. Iterating over collections in SQL is significantly faster than in PL/SQL. CREATE TYPE PERIOD AS OBJECT ( beginning DATE, ending DATE, ... some member functions...); CREATE TYPE PERIOD_TABLE AS TABLE OF PERIOD; -- sample usage SELECT <<period object>>.contains(period2) FROM TABLE(period_table1) t The problem is that the TABLE() function explodes the objects into scalar values, and I really need the objects instead. I could use the scalar values to recreate the objects but this would incur the overhead of re-instantiating the objects. And the period is designed to be subclassed so there would be additional difficulty trying to figure out what to initialize it as. Is there another way to do this that doesn't destroy my objects?

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• How to populate an array with recordset data

  - by Curtis Inderwiesche

  I am attempting to move data from a recordset directly into an array. I know this is possible, but specifically I want to do this in VBA as this is being done in MS Access 2003. Typically I would do something like the following to archive this: Dim vaData As Variant Dim rst As ADODB.Recordset ' Pull data into recordset code here... ' Populate the array with the whole recordset. vaData = rst.GetRows What differences exist between VB and VBA which makes this type of operation not work? What about performance concerns? Is this an "expensive" operations?

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• Testing perceived performance

  - by Josh Kelley

  I recently got a shiny new development workstation. The only disadvantage of this is that the desktop apps I'm developing now run very, very fast, and so I fear that parts of the code that would be annoyingly slow on end users' machines will go unnoticed during my testing. Is there a good way to slow down an application for testing? I've tried searching around, but all of the results I've been able to find seem pretty fiddly to set up (e.g., manually setting up a high-priority CPU-bound task on the same CPU core as the target app, or running a background process that rapidly interrupts and resumes the target app), and I don't know if the end result is actually a good representation of running on a slower computer (with its slower CPU, slower RAM, slower disk I/O...). I don't think that this is a job for a profiler; I'm interested in the user's perception of end-to-end performance rather than in where the time goes for particular operations.

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• Looking for actively maintained matrix math library for php

  - by Mnebuerquo

  Does anyone know where I might find a PHP matrix math library which is still actively maintained? I need to be able to do the basic matrix operations like reduce, transpose (including non-square matrices), invert, determinant, etc. This question was asked in the past, then closed with no answers. Now I need an answer to the same question. See these links to related questions: http://stackoverflow.com/questions/428473/matrix-artihmetic-in-php http://stackoverflow.com/questions/435074/matrix-arithmetic-in-php-again I was in the process of installing the pear Math_Matrix library when I saw these and realized it wouldn't help me. (Thanks Ben for putting that comment about transpose in your question.) I can code this stuff myself, but I would make me happier to see that there is a library for this somewhere.

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