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Search found 382 results on 16 pages for 'numerical'.

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• I need a decent alternative to c++ [closed]

  - by wxiiir

  I've learned php and c++, i will list the things i liked and didn't liked on each of them, how i decided to learn them in the first place and why i feel the need to learn a decent alternative to c++, i'm not a professional programmer and only do projects for myself. PHP - Decided to learn because i wanted to build a dynamic website, that i did and turned out very good, i even coded a 'not so basic' search engine for it that would display the results 'google style' and really fast, pretty cool stuff. PROS - Pretty consistent syntax for all stuff (minor caveats), great functionality, a joy for me to code in it (it seems to 'know' what i want it to do and just does it) CONS - Painfully slow for number crunching (which takes me to c++ that i only learned because i wanted to do some number crunching and it had to be screaming fast) C++ - Learned because number crunching was so slow in php and manipulating large amounts of data was very difficult, i thought, it's popular programming language and all, and tests show that it's fast, the basic stuff resemble php so it shouldn't be hard to pick up PROS - It can be used to virtually anything, very very fast CONS - Although fun to code at the start, if i need to do something out of the ordinary, memory allocation routines, pointer stuff, stack sizes etc... will get me tired really quick, syntax is a bit inconsistent some times (more caveats) I guess that from what i wrote you guys will understand what i'm looking for, there are thousands of languages out there, it's likely that one of them will suit my needs, i've been seeing stuff today and a friend of mine that is a professional programmer tried OCaml and Fortran and said that both are fast for numerical stuff, i've been inclined to test Fortran, but i need some more input because i want to have some other good 'candidates' to choose from, for example the python syntax seemed great to me, but then i found out from some tests that it was a lot slower than c++ and i simply don't want to twiddle my thumbs all day.

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• Referencing variables in a structure / C++

  - by user1628622

  Below, I provided a minimal example of code I created. I managed to get this code working, but I'm not sure if the practice being employed is sound. In essence, what I am trying to do is have the 'Parameter' class reference select elements in the 'States' class, so variables in States can be changed via Parameters. Questions I have: is the approach taken OK? If not, is there a better way to achieve what I am aiming for? Example code: struct VAR_TYPE{ public: bool is_fixed; // If is_fixed = true, then variable is a parameter double value; // Numerical value std::string name; // Description of variable (to identify it by name) }; struct NODE{ public: VAR_TYPE X, Y, Z; /* VAR_TYPE is a structure of primitive types */ }; class States{ private: std::vector <NODE_ptr> node; // shared ptr to struct NODE std::vector <PROP_DICTIONARY_ptr> property; // CAN NOT be part of Parameter std::vector <ELEMENT_ptr> element; // CAN NOT be part of Parameter public: /* ect */ void set_X_reference ( Parameter &T , int i ) { T.push_var( &node[i]->X ); } void set_Y_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Y ); } void set_Z_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Z ); } bool get_node_bool_X( int i ) { return node[i]->X.is_fixed; } // repeat for Y and Z }; class Parameter{ private: std::vector <VAR_TYPE*> var; public: /* ect */ }; int main(){ States S; Parameter P; /* Here I initialize and set S, and do other stuff */ // Now I assign components in States to Parameters for(int n=0 ; n<S.size_of_nodes() ; n++ ){ if ( S.get_node_bool_X(n)==true ){ S.set_X_reference ( P , n ); }; // repeat if statement for Y and Z }; /* Now P points selected to data in S, and I can * modify the contents of S through P */ return 0; }; Update The reason this issue cropped up is I am working with Fortran legacy code. To sum up this Fotran code - it's a numerical simulation of a flight vehicle. This code has a fairly rigid procedural framework one must work within, which comes with a pre-defined list of allowable Fortran types. The Fortran glue code can create an instance of a C++ object (in actuality, a reference from the perspective of Fortran), but is not aware what is contained in it (other means are used to extract C++ data into Fortran). The problem that I encountered is when a C++ module is dynamically linked to the Fortran glue code, C++ objects have to be initialized each instance the C++ code is called. This happens by virtue of how the Fortran template is defined. To avoid this cycle of re-initializing objects, I plan to use 'State' as a container class. The Fortran code allows a 'State' object, which has an arbitrary definition; but I plan to use it to harness all relevant information about the model. The idea is to use the Parameters class (which is exposed and updated by the Fortran code) to update variables in States.

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• Run VBA macro when condition is met

  - by Pieter

  Hello all, I'm creating a spreadsheet to train my numerical skills. Now, I use VBA macros to generate a new problem once the current one has been correctly solved. To do so, I still have to press a button in the worksheet, which costs time and is annoying. Is there a way that I can execute a macro when a certain condition is met? for instance: if A1 = "correct!" then <run macro> else <do nothing> Also, let me know if you're interested in the spreadsheet, I'd be happy to share it with you guys. best, Pieter

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• Controlling FPU behavior in an OpenMP program?

  - by STingRaySC

  I have a large C++ program that modifies the FPU control word (using _controlfp()). It unmasks some FPU exceptions and installs a SEHTranslator to produce typed C++ exceptions. I am using VC++ 9.0. I would like to use OpenMP (v.2.0) to parallelize some of our computational loops. I've already successfully applied it to one, but the numerical results are slightly different (though I understand it could also be due to calculations being performed in a different order). I'm assuming this is because the FPU state is thread-specific. Is there some way to have the OpenMP threads inherit that state from the master thread? Or is there some way to specify using OpenMP that new threads execute a particular function that sets up the correct state? What is the idiomatic way to deal with this situation?

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• Hashing words to numbers with respect to definition

  - by thornate

  As part of a larger project, I need to read in text and represent each word as a number. For example, if the program reads in "Every good boy deserves fruit", then I would get a table that converts 'every' to '1742', 'good' to '977513', etc. Now, obviously I can just use a hashing algorithm to get these numbers. However, it would be more useful if words with similar meanings had numerical values close to each other, so that 'good' becomes '6827' and 'great' becomes '6835', etc. As another option, instead of a simple integer representing each number, it would be even better to have a vector made up of multiple numbers, eg (lexical_category, tense, classification, specific_word) where lexical_category is noun/verb/adjective/etc, tense is future/past/present, classification defines a wide set of general topics and specific_word is much the same as described in the previous paragraph. Does any such an algorithm exist? If not, can you give me any tips on how to get started on developing one myself? I code in C++.

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• DataMining / Analyzing responses to Multiple Choice Questions in a survey

  - by Shailesh Tainwala

  Hi, I have a set of training data consisting of 20 multiple choice questions (A/B/C/D) answered by a hundred respondents. The answers are purely categorical and cannot be scaled to numerical values. 50 of these respondents were selected for free product trial. The selection process is not known. What interesting knowledge can be mined from this information? The following is a list of what I have come up with so far- A study of percentages (Example - Percentage of people who answered B on Qs.5 and got selected for free product trial) Conditional probabilities (Example - What is the probability that a person will get selected for free product trial given that he answered B on Qs.5) Naive Bayesian classifier (This can be used to predict whether a person will be selected or not for a given set of values for any subset of questions). Can you think of any other interesting analysis or data-mining activities that can be performed? The usual suspects like correlation can be eliminated as the response is not quantifiable/scoreable. Is my approach correct?

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• Decode sparse json array to php array

  - by Isaac Sutherland

  I can create a sparse php array (or map) using the command: $myarray = array(10=>'hi','test20'=>'howdy'); I want to serialize/deserialize this as JSON. I can serialize it using the command: $json = json_encode($myarray); which results in the string {"10":"hi","test20":"howdy"}. However, when I deserialize this and cast it to an array using the command: $mynewarray = (array)json_decode($json); I seem to lose any mappings with keys which were not valid php identifiers. That is, mynewarray has mapping 'test20'=>'howdy', but not 10=>'hi' nor '10'=>'hi'. Is there a way to preserve the numerical keys in a php map when converting to and back from json using the standard json_encode / json_decode functions?

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• using a php variable in the WHERE clause of a mysql query

  - by user1262890

  I'm running a very simple query that I think should work. The only thing that I haven't done before is put a php variable in the WHERE clause of the query. The variable $X is a numerical value, say 100. When I run this query, I just get a value of 0 returned. Am I doing something obviously stupid? SELECT generator_64k.n FROM generator_64k WHERE generator_64k.n<= '$X' I've looked around the web and also tried this: SELECT generator_64k.n FROM generator_64k WHERE generator_64k.n<= '" . $X . "' But this also just returns 0. Any ideas? Thanks in advance.

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• Large number array compression

  - by gatapia

  Hi All, I've got a javascript application that sends a large amount of numerical data down the wire. This data is then stored in a database. I am having size issues (too much bandwidth, database getting too big). I am now ready to sacrifice some performance for compression. I was thinking of implementing a base 62 number.toString(62) and parseInt(compressed, 62). This would certainly reduce the size of the data but before I go ahead and do this I thought I would put it to the folks here as I know there must be some outside the box solution I have not considered. The basic specs are: - Compress large number arrays into strings for JSONP transfer (So I think UTF is out) - Be relatively fast, look I'm not expecting same performance as I have now but I also don't want gzip compression either. Any ideas would be greatly appreciated. Thanks Guido Tapia

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• iPad UIColor Saturation Issues

  - by Carter Allen

  I am trying to draw a UIColor on the screen of a view-based app, and I am trying to do so using HSB. It is absolutely necessary for me to use HSB in this case. I can create a UIColor object with any S value from 0.0f to 0.75f, but past that the numerical changes have no effect on the actual saturation displayed. I need it to be 1.0f, but it is still using 0.75f. Any ideas on why it is doing that, and how I can make it work?

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• Python Least-Squares Natural Splines

  - by Eldila

  I am trying to find a numerical package which will fit a natural which minimizes weighted least squares. There is a package in scipy which does what I want for unnatural splines. import numpy as np import matplotlib.pyplot as plt from scipy import interpolate import random x = np.arange(0,5,1.0/2) xs = np.arange(0,5,1.0/500) y = np.sin(x+1) for i in range(len(y)): y[i] += .2*random.random() - .1 knots = np.array([1,2,3,4]) tck = interpolate.splrep(x,y,s=1,k=3,t=knots,task=-1) ynew = interpolate.splev(xs,tck,der=0) plt.figure() plt.plot(xs,ynew,x,y,'x')

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• double_t in C99

  - by yCalleecharan

  Hi, I just read that C99 has double_t which should be at least wide as double. Does this imply that it gives more precision digits after the decimal place? More than the usual 15 digits for double?. Secondly, how to use it: Is only including #include enough? I read that one has to set the FLT_EVAL_METHOD to 2 for long double. How to do this? As I work with numerical methods, I would like maximum precision without using an arbitrary precision library. Thanks a lot...

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• PInvoke or using /clr:pure to compile

  - by Yin Zhu

  I have a set of numerical libraries in C++ and I want to call them interactively in a interpretive language like F# or IronPython. So I have two choices now: Compile the library in native DLL and use PInvoke to call functions in it. Compile the C++ library to .Net dll using visual c++ (/clr:pure compile option). The advantage of 1 is that it is very fast, however there are more work in it, e.g. I cannot PInvoke double pointer (e.g. float **), I must write another wrapper in the C++ library to make the interface friendly to .Net. The advantage of 2 is that I don't need to do know Mashaling strings, arrays, etc. However, the .net dll is slower compared to the native one. What others factors should be considered when choosing between the two?

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• An error which does not present itself with a debugger attached.

  - by ccook

  I am using Intel's FORTRAN compiler to compile a numerical library. The test case provided errors out within libc.so.6. When I attach Intel's debugger (IDB) the application runs through successfully. How do I debug a bug where the debugger prevents the bug? Note that the same bug arose with gfortran. I am working within OpenSUSE 11.2 x64. The error is: forrtl: severe (408): fort: (3): Subscript #1 of the array B has value -534829264 which is less than the lower bound of 1

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• Pass associative arrays in call_user_func_array(...)

  - by Matt

  Hey all, I'm building a templating system and I'm running in to an issue with calling functions on the fly. When I try the following: $args = array( 4, 'test' => 'hello', 'hi' ); You know.. some numerical elements some associative elements, call_user_func_array($function, $args); converts the array to something like this: $args = array( 4, 'hello', 'hi' ); Is there any way around this other than passing an array like this: $args = array( 4, array('test' => 'hello'), 'hi' ); Thanks! Matt

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• side effect gotchas in python/numpy? horror stories and narrow escapes wanted

  - by shabbychef

  I am considering moving from Matlab to Python/numpy for data analysis and numerical simulations. I have used Matlab (and SML-NJ) for years, and am very comfortable in the functional environment without side effects (barring I/O), but am a little reluctant about the side effects in Python. Can people share their favorite gotchas regarding side effects, and if possible, how they got around them? As an example, I was a bit surprised when I tried the following code in Python: lofls = [[]] * 4 #an accident waiting to happen! lofls[0].append(7) #not what I was expecting... print lofls #gives [[7], [7], [7], [7]] #instead, I should have done this (I think) lofls = [[] for x in range(4)] lofls[0].append(7) #only appends to the first list print lofls #gives [[7], [], [], []] thanks in advance

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• Gaining information from nodes of tree

  - by jainp

  I am working with the tree data structure and trying to come up with a way to calculate information I can gain from the nodes of the tree. I am wondering if there are any existing techniques which can assign higher numerical importance to a node which appears less frequently at lower level (Distance from the root of the tree) than the same nodes appearance at higher level and high frequency. To give an example, I want to give more significance to node Book, at level 2 appearing once, then at level 3 appearing thrice. Will appreciate any suggestions/pointers to techniques which achieve something similar. Thanks, Prateek

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• Where can I find simple beta cdf implementation.

  - by Gacek

  I need to use beta distribution and inverse beta distribution in my project. There is quite good but complicated implementation in GSL, but I don't want to use such a big library only to get one function. I would like to either, implement it on my own or link some simple library. Do you know any sources that could help me? I'm looking for any books/articles about numerical approximation of beta PDF, libraries where it could be implemented. Any other suggestions would be also appreciated. Any programming language, but C++/C# preffered.

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• Equivalent of LaTeX's \label and \ref in HTML.

  - by dreeves

  I have an FAQ in HTML (example) in which the questions refer to each other a lot. That means whenever we insert/delete/rearrange the questions, the numbering changes. LaTeX solves this very elegantly with \label and \ref -- you give items simple tags and LaTeX worries about converting to numbers in the final document. How do people deal with that in HTML? ADDED: Note that this is no problem if you don't have to actually refer to items by number, in which case you can set a tag with <a name="foo"> and then link to it with <a href="#foo">some non-numerical way to refer to foo</a>. But I'm assuming "foo" has some auto-generated number, say from an <ol> list, and I want to use that number to refer to and link to it.

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• pgf/tikz: String Symbols as Input Coordinates

  - by red_lynx

  Hi all, I'm new to pgf so i was trying out some examples from the pgfplot manual. One example is especially relevant for my current task but, alas, it would not compile. Here is the code: \documentclass[11pt]{article} \usepackage{tikz} \usepackage{pgfplots} \begin{document} \begin{tikzpicture} \begin{axis}[symbolic x coords={a,b,c,d,e,f,g,h,i}] \addplot+[smooth] coordinates { (a,42) (b,50) (c,80) (f,60) (g,62) (i,90)}; \end{axis} \end{tikzpicture} \end{document} the compiler quits with the following error: ! Package PGF Math Error: Could not parse input 'a' as a floating point number, sorry. The unreadable part was near 'a'.. I have no clue how to correct this behavior. Other plots (smooth, scatter, bar), which contain only numerical data compile fine. Could anybody give me a hint? Cheers K.

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• C++ password masking

  - by blaxc

  hi... i'm writing a code to receive password input. Below is my code... the program run well but the problem is other keys beside than numerical and alphabet characters also being read, for example delete, insert, and etc. can i know how can i avoid it? tq... string pw=""; char c=' '; while(c != 13) //Loop until 'Enter' is pressed { c = _getch(); if(c==13) break; if(c==8) { if(pw.size()!=0) //delete only if there is input { cout<<"\b \b"; pw.erase(pw.size()-1); } } if((c>47&&c<58)||(c>64&&c<91)||(c>96&&c<123)) //ASCii code for integer and alphabet { pw += c; cout << "*"; } }

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• c# Regex on XML string handler

  - by Dan Sewell

  Hi guys. Trying to fiddle around with regex here, my first attempt. Im trying to extract some figures out of content from an XML tag. The content looks like this: www.blahblah.se/maps.aspx?isAlert=true&lat=51.958855252721&lon=-0.517657021473527 I need to extract the lat and long numerical vales out of each link. They will always be the same amount of characters, and the lon may or may not have a "-" sign. I thought about doing something like this below: (The string in question is in the "link" tag): var document = XDocument.Load(e.Result); if (document.Root == null) return; var events = from ev in document.Descendants("item1") select new { Title = (ev.Element("title").Value), Latitude = Regex.xxxxxxx(ev.Element("link").Value, @"lat=(?<Lat>[+-]?\d*\.\d*)", String.Empty), Longitude = Convert.ToDouble(ev.Element("link").Value), }; foreach (var ev in events) { do stuff } Many thanks!

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• Capture String from Array, C#

  - by Dan Snyder

  I'm trying to figure out how to get a string from an array starting at some given position. Say we have an array that's arbitrarily long and my string starts at location 1000. If I wanted to get a string from a file I would simply use something like getc or scanf or something. How do I carry out these same functions on an array instead of a file? *oh, keep in mind that the array is of type int and is full of numerical representations of ASCII characters.

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• Validating an integer or String without try-catch

  - by Phil

  Ok, I'm lost. I am required to figure out how to validate an integer and String, but for some stupid reason, I can't use the Try-Catch method. I know this is the easiest way and so all the solutions on the internet are using it. I'm writing in Java. The deal is this, I need someone to put in an numerical ID and String name. If either one of the two inputs are invalid I must tell them they made a mistake. Can someone help me?

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• Doctrine enum type by value

  - by MitMaro

  I have a column in a table defined as following in my yaml file: myTable: columns: value: type: enum length: 2 values: ['yes', 'no'] In the code I am trying to insert data into this table but I can't figure out a way to insert the data using the enum text value (ie. 'yes' or 'no'). What I was trying was is something like this: $obj = new myTable(); // the model for this table $obj->value = 'yes'; // if I use the numerical value for this it works I am using Doctrine 1.1.0.

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