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  • HOw to Extract image pixels and perform computation on it

    - by gavishna
    What i want to do is extract the pixels into array A(i,j).Let A(i,j) represent the pixel in the ith row & jth colm of the image. Let B(i,j) be the transformed array containing bits such that B(i,j) = 1 if (A(i,j)/2^t) mod 2 =1, where t=0,1,2,3,4,5,6,7 = 0 otherwise Then the array B(i,j) will be mutliplied by another array say C(i,j) representing another image. Then i want to plot the result of B*C as an image. How do i take in the pixels for the above conditions for both gray and RGB color format.Also how do i solve the above problem.Any helo will be usefull because i am not an expert in image processing.

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  • numerical computation locks up ruby

    - by kolosy
    i'm trying to implement an id obfuscation scheme, with a simple hash borrowed elsewhere. i've added a method on the application helper: @@M_ID = 2**31-1 @@PRIME = 1580030173 @@PRIME_INVERSE = 59260789 # (calculated from MAXID and PRIME offline) def obfuscate_id(x) if x return ((x * @@PRIME) & @@M_ID) else x end end for some reason, whenever this is called, ruby locks up, and starts eating up disk space on my mac... like - gigs of it. any ideas?

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  • Parallel computation of the median of a large array

    - by recipriversexclusion
    I got asked this question once and still haven't been able to figure it out: You have an array of N integers, where N is large, say, a billion. You want to calculate the median value of this array. Assume you have m+1 machines (m workers, one master) to distribute the job to. How would you go about doing this? Since the median is a nonlinear operator, you can't just find the median in each machine and then take the median of those values.

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  • optimization math computation (multiplication and summing)

    - by wiso
    Suppose you want to compute the sum of the square of the differences of items: $\sum_{i=1}^{N-1} (x_i - x_{i+1})^2$, the simplest code (the input is std::vector<double> xs, the ouput sum2) is: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (prev - (*i)) * (prev - (*i)); // only 1 - with compiler optimization prev = (*i); } I hope that the compiler do the optimization in the comment above. If N is the length of xs you have N-1 multiplications and 2N-3 sums (sums means + or -). Now suppose you know this variable: sum = $x_1^2 + x_N^2 + 2 sum_{i=2}^{N-1} x_i^2$ Expanding the binomial square: $sum_i^{N-1} (x_i-x_{i+1})^2 = sum - 2\sum_{i=1}^{N-1} x_i x_{i+1}$ so the code becomes: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (*i) * prev; prev = (*i); } sum2 = -sum2 * 2. + sum; Here I have N multiplications and N-1 additions. In my case N is about 100. Well, compiling with g++ -O2 I got no speed up (I try calling the inlined function 2M times), why?

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  • aov define F values computation

    - by essopapas
    Greetings to all This is my model: aov.fit<-aov(Y~A+B+C+D+E+A:C+A:E, data=dat) In summary(aov.fit) all F values are comptuted by eg MS(A)/MS(Residuals). This is not correct (or what I want), except for F(B) and F(A:E). I suppose P values are not correct either. Can I specify how the F computations will be done? I 'd like them to be like this: F(A)=MS(A)/MS(E), F(C)=MS(C)/MS(E), F(D)=MS(D)/MS(E), F(E)=MS(E)/MS(A:E), F(A:C)=MS(A:C)/MS(A:E) thanks

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  • New Regular Expression Features in Java 8

    - by Jan Goyvaerts
    Java 8 brings a few changes to Java’s regular expression syntax to make it more consistent with Perl 5.14 and later in matching horizontal and vertical whitespace. \h is a new feature. It is a shorthand character class that matches any horizontal whitespace character as defined in the Unicode standard. In Java 4 to 7 \v is a character escape that matches only the vertical tab character. In Java 8 \v is a shorthand character class that matches any vertical whitespace, including the vertical tab. When upgrading to Java 8, make sure that any regexes that use \v still do what you want. Use \x0B or \cK to match just the vertical tab in any version of Java. \R is also a new feature. It matches any line break as defined by the Unicode standard. Windows-style CRLF pairs are always matched as a whole. So \R matches \r\n while \R\R fails to match \r\n. \R is equivalent to (?\r\n|[\n\cK\f\r\u0085\u2028\u2029]) with an atomic group that prevents it from matching only the CR in a CRLF pair. Oracle’s documentation for the Pattern class omits the atomic group when explaining \R, which is incorrect. You cannot use \R inside a character class. RegexBuddy and RegexMagic have been updated to support Java 8. Java 4, 5, 6, and 7 are still supported. When you upgrade to Java 8 you can compare or convert your regular expressions between Java 8 and the Java version you were using previously.

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  • Sampler referencing in HLSL - Sampler parameter must come from a literal expression

    - by user1423893
    The following method works fine when referencing a sampler in HLSL float3 P = lightScreenPos; sampler ShadowSampler = DPFrontShadowSampler; float depth; if (alpha >= 0.5f) { // Reference the correct sampler ShadowSampler = DPFrontShadowSampler; // Front hemisphere 'P0' P.z = P.z + 1.0; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; } else { // Reference the correct sampler ShadowSampler = DPBackShadowSampler; // Back hemisphere 'P1' P.z = 1.0 - P.z; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; } // [Standard Depth Calculation] float mydepth = P.z; shadow = depth + Bias.x < mydepth ? 0.0f : 1.0f; If I try and do anything with the sampler reference outside the if statement then I get the following error: Sampler parameter must come from a literal expression This code demonstrates that float3 P = lightScreenPos; sampler ShadowSampler = DPFrontShadowSampler; if (alpha >= 0.5f) { // Reference the correct sampler ShadowSampler = DPFrontShadowSampler; // Front hemisphere 'P0' P.z = P.z + 1.0; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; } else { // Reference the correct sampler ShadowSampler = DPBackShadowSampler; // Back hemisphere 'P1' P.z = 1.0 - P.z; P.x = P.x / P.z; P.y = P.y / P.z; P.z = lightLength / LightAttenuation.z; } // Rescale viewport to be [0, 1] (texture coordinate space) P.x = 0.5f * P.x + 0.5f; P.y = -0.5f * P.y + 0.5f; // [Standard Depth Calculation] float depth = tex2D(ShadowSampler, P.xy).x; depth = 1.0 - depth; float mydepth = P.z; shadow = depth + Bias.x < mydepth ? 0.0f : 1.0f; How can I reference the sampler in this manner without triggering the error?

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  • Regular expression not working after debugging

    - by Jaison
    I have an ASP.NET website with a regular expression validator text box. I have changed the expression in the regular expression validation property "validator expression" and after compiling (rebuild) and running, the validation CHANGEs are not reflecting. The previous validation is working fine but the changed validation is not working. Please help me! edit: First code: ([a-zA-Z0-9_-.]+)\@((base.co.uk)|(base.com)|(group.com)) Second code: @"([a-zA-Z0-9_\-.]+)@((base\.co\.uk)|(base\.com)|(group\.com)|(arg\.co\.uk)|(arggroup\.com))"

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  • C++ Expression Templates

    - by yCalleecharan
    Hi, I currently use C for numerical computations. I've heard that using C++ Expression Templates is better for scientific computing. What are C++ Expression Templates in simple terms? Are there books around that discuss numerical methods/computations using C++ Expression Templates? In what way, C++ Expression Templates are better than using pure C? Thanks a lot

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  • Why isn't Expression Blend rendering my User Control? It's only showing XAML.

    - by unforgiven3
    I'm opening valid XAML within my VS2008 solution in Expression Blend 3 and it is only showing XAML when I try to open individual XAML files. My solution/projects all build and run correctly. When I go to View - Active Document View the Design View, Split View and XAML View options are all grayed out... which doesn't make much sense. I'm not much of a Blend user, but this has never happened before, and I'm coming up blank for how to fix it. Any ideas?

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  • How can I generate an Expression tree that queries an object with List<T> as a property?

    - by David Robbins
    Forgive my clumsy explanation, but I have a class that contains a List: public class Document { public int OwnerId { get; set; } public List<User> Users { get; set; } public Document() { } } public class User { public string UserName { get; set; } public string Department { get; set; } } Currently I use PredicateBuilder to perform dynmica queries on my objects. How can I turn the following LINQ statement into an Expression Tree: var predicate= PredicateBuilder.True<User>(); predicate= predicate.And<User>(user => user.Deparment == "HR"); var deptDocs = documents.AsQueryable() .Where(doc => doc.Users .AsQueryable().Count(predicate) > 0) .ToList(); In other words var deptDocs = documents.HasUserAttributes("Department", "HR").ToList();

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  • Expression Encoder - Limitations for file Dimension - min size of 64 * 64 and must be a multiple of

    - by PortageMonkey
    I receive error messages when attempting to encode files in Expression Encoder when the file width or height is not a multiple of four, or is smaller than 64. I have been able to find very little in the documentation / web searches on this, and nothing that explains what settings may cause / alleviate these limitations. I assume it has something to do with the underlying data type. Error Message: Invalid Width Specified. The value must be an integer between 64 - and 4096 and be a multiple of 4. Can anyone provide further details on why / what settings can be manipulated to change this behavior: I.E. quality, compression etc.

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  • How to resize a group of vectors in Expression Blend/WPF/Silverlight ?

    - by Shnitzel
    So say for example I created a few small squares in expression blend. I then group them together by selecting them, right clicking and selecting "Group Into - Grid" So now that they are in the grid, I'd like to be able to resize this grid and then they would resize but it doesn't happen, it just resizes the grid but leaves the vectors the same. Is there a way to do what I am looking for? p.s I know you can just select all the vectors and then resize them all, but I am looking for a way to just resize one container and not all the objects in there..

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  • WPF: In Expression Blend, how to change Foreground of a custom button with a Border on different states?

    - by SubmarineX
    In Expression Blend 4, I want to change the Foreground of a custom button on different states. I'm just able to change the Background and BorderBrush. Just like this: If the state is "Normal", the color of text "Button" is Black, while the state is "Pressed", the color of text "Button" is White. On Brushes Panel under Properties Panel, there're 3 properties but no Foreground property: Who can help me? I'm so perplexed. Edit I find ContentControl have a Foreground property, but ContentPresenter haven't. Wether I should use ContentControl instead of ContentPresenter?

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  • Wrong assembly-references for Silverlight Sketchflow project in Blend 3

    - by persistent
    Hello, In my installation of Blend 3, the SketchStyles are missing when a new project is created. I found out that this is because the following automatic references in the project are wrong: Microsoft.Expression.Interactions Microsoft.Expression.Prototyping.Interactivity Microsoft.Expression.Prototyping.RunTime Microsoft.Expression.Prototyping.SketchControls In the project references these all point to my project path (where they don't live). If I remove them manually, and instead set the references to ie this: "c:\Program Files (x86)\Microsoft SDKs\Expression\Blend 3\Interactivity\Libraries\Silverlight\Microsoft.Expression.Interactions.dll" everything works. Any ideas on why, and how to fix this? Could it be the project template somehow? TIA

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  • C++ infix to postfix conversion for logical conditions

    - by Gopalakrishnan Subramani
    I want to evaluate one expression in C++. To evaluate it, I want the expression to be converted to prefix format. Here is an example wstring expression = "Feature1 And Feature2"; Here are possible ways. expression = "Feature1 And (Feature2 Or Feature3)"; expression = "Not Feature1 Or Feature3"; Here And, Or, Not are reserved words and parentheses ("(", )) are used for scope Not has higher precedence And is set next precedence to Not Or is set to next precedence to And WHITE SPACE used for delimiter. Expression has no other elements like TAB, NEWLINE I don't need arithmetic expressions. I can do the evaluation but can somebody help me to convert the strings to prefix notation?

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  • Watchguard Firewall WebBlocker Regular Expression for Multiple Domains?

    - by Eric
    I'm pretty sure this is really a regex question, so you can skip to REGEX QUESTION if you want to skip the background. Our primary firewall is a Watchguard X750e running Fireware XTM v11.2. We're using webblocker to block most of the categories, and I'm allowing needed sites as they arise. Some sites are simple to add as exceptions, like Pandora radio. That one is just a pattern matched exception with "padnora.com/" as the pattern. All traffic from anywhere on pandora.com is allowed. I'm running into trouble on more sophisticated domains that reference content off of their base domains. We'll take GrooveShark as a sample. If you go to http://grooveshark.com/ and view page source, you'll see hrefs referring to gs-cdn.net as well as grooveshar.com. So adding a WebBlocker exception to grooveshark.com/ is not effective, and I have to add a second rule allowing gs-cdn.net/ as well. I see that the WebBlocker allows regex rules, so what I'd like to do in situations like this is create a single regex rule that allows traffic to all the needed domains. REGEX QUESTION: I'd like to try a regex that matches grooveshark.com/ and gs-cdn.net/. If anybody can help me write that regex, I'd appreciate it. Here is what is in the WatchGuard documentation from that section: Regular expression Regular expression matches use a Perl-compatible regular expression to make a match. For example, .[onc][eor][gtm] matches .org, .net, .com, or any other three-letter combination of one letter from each bracket, in order. Be sure to drop the leading “http://” Supports wild cards used in shell script. For example, the expression “(www)?.watchguard.[com|org|net]” will match URL paths including www.watchguard.com, www.watchguard.net, and www.watchguard.org. Thanks all!

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  • How do I optimize this postfix expression tree for speed?

    - by Peter Stewart
    Thanks to the help I received in this post: I have a nice, concise recursive function to traverse a tree in postfix order: deque <char*> d; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } d.push_front(cargo); return; }; This is an expression tree. The branch nodes are operators randomly selected from an array, and the leaf nodes are values or the variable 'x', also randomly selected from an array. char *values[10]={"1.0","2.0","3.0","4.0","5.0","6.0","7.0","8.0","9.0","x"}; char *ops[4]={"+","-","*","/"}; As this will be called billions of times during a run of the genetic algorithm of which it is a part, I'd like to optimize it for speed. I have a number of questions on this topic which I will ask in separate postings. The first is: how can I get access to each 'cargo' as it is found. That is: instead of pushing 'cargo' onto a deque, and then processing the deque to get the value, I'd like to start processing it right away. I don't yet know about parallel processing in c++, but this would ideally be done concurrently on two different processors. In python, I'd make the function a generator and access succeeding 'cargo's using .next(). But I'm using c++ to speed up the python implementation. I'm thinking that this kind of tree has been around for a long time, and somebody has probably optimized it already. Any Ideas? Thanks

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  • List of events triggered on pages matching regex

    - by Cubius
    Is there a way to get the grouped list of events (such as in Top events) which were triggered on pages matching a regular expression? I may add the Page secondary dimension in Top events and apply the regex filter but this way I won't get a grouped list. I may apply the filter to Events - Pages report but this way the events will be grouped only inside pages whilst I need global grouping. Any suggestions?

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  • How to use SQL Expression Fields of Crystal Report 11.5 from VB.NET 2008

    - by Tareq
    I have the following SQL Expression Field in my Crystal Report 11.5 {fn CONCAT({fn CONCAT("SPR_PRODUCT"."PRODUCT_ID","SPR_PRODUCT_SUB_ITEM"."P_SUB_ITEM_ID" )},{fn CONCAT("SPR_PRODUCT_ITEM"."P_ITEM_ID","SPR_PRODUCT_GROUP"."P_GROUP_ID" )} )} It works well in the Preview Mode. But when I use the report in my VB.NET 2008 Project it says the following: Error in compiling SQL Expression : SQL Expressions can not be used in this report.. Error in File <...>.rpt: SQL Expression error: Error in compiling SQL Expression : SQL Expressions can not be used in this report... Please help me by telling how can I use the SQL Expression field in VB.NET ? Thanks in Advance.

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  • Regular expression to validate name in .NET multilingual web application

    - by BT
    Hi, how can i write a regular expression to validate name field in a multilingual web application, i want to validate the name field for non-English languages e.g. Spanish or German, and we need to make sure that no one enter digits or special characters. I'm using .NET. I believe we can't use expression as below for non-English language. ^[a-zA-Z]{1,20}$ Any help will be highly appreciated! Solution: I'm using this regular expression ^\p{L}[\p{L}\p{Pd}\x27]*\p{L}$ , and the below MSISDN article was very helpful: MSDN - Regular Expression Also below tool is very helpful, in validating your regular expression: Regex Builder

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  • How to Expression.Invoke an arbitrary LINQ 2 SQL Query

    - by Remus Rusanu
    Say I take an arbitrary LINQ2SQL query's Expression, is it possible to invoke it somehow? MyContext ctx1 = new MyContext("..."); var q = from t in ctx1.table1 where t.id = 1 select t; Expression qe = q.Expression; var res = Expression.Invoke(qe); This throws ArgumentException "Expression of type System.Linq.IQueryable`1[...]' cannot be invoked". My ultimate goal is to evaluate the same query on several different data contexts.

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