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Search found 38 results on 2 pages for 'ycalleecharan'.

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  • malloc: error checking and freeing memory

    - by yCalleecharan
    Hi, I'm using malloc to make an error check of whether memory can be allocated or not for the particular array z1. ARRAY_SIZE is a predefined with a numerical value. I use casting as I've read it's safe to do so. long double *z1 = (long double *)malloc(sizeof (long double) * ARRAY_SIZE); if(z1 == NULL){ printf("Out of memory\n"); exit(-1); } The above is just a snippet of my code, but when I add the error checking part (contained in the if statement above), I get a lot of compile time errors with visual studio 2008. It is this error checking part that's generating all the errors. What am I doing wrong? On a related issue with malloc, I understand that the memory needs to be deallocated/freed after the variable/array z1 has been used. For the array z1, I use: free(z1); z1 = NULL; Is the second line z1 = NULL necessary? Thanks a lot...

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  • thesis in LaTeX without memoir

    - by yCalleecharan
    Hi, I'm preparing a thesis report in LaTeX. I don't want to use the memoir class as I would like total control. I have two questions: My thesis consists of an introduction and then a series of articles pasted one after the other. Thus each article has its own abstract, introduction, etc... and a bibliography at its end. I understand that perhaps a package like multibib can help when we have multiple bibliographies. The idea that I came with is to write each article separately and then use pdfpages to combine the final document. Long time ago dvi files concatenation was popular but with graphics I think that pdfpages is better. I saw that another package exists, named combine which can help with what I am doing. I'm still exploring my options. Any suggestions? If I decide to use a book class instead to make my thesis resemble more into a book-like format which is better, then using the book class format gives me section headings like 0.1 Introduction with the leading 0. This 0 doesn't show in the article class format. How to change this default book class numbering format so that I'll have e.g. 1. Introduction? Thanks a lot...

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  • MVS 2008 and C99

    - by yCalleecharan
    Hi, I read with interest the post "How universally is C99 supported ?". One of the comments therein points that Microsoft doesn't support C99. But the comment symbol // works with MVS 2008 and this symbol is in C99. I have two questions: To what extent MVS 2008 support C99? Is it ok in the same code to mix C89 and C99 syntax together? So if I write my code in C89 and then place a comment //. This means that I have mixed-coding. So what does the compiler do in such a case? Check my code first with c89 and then with C99 to accept that I use // for commenting? Thanks a lot...

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  • C99 and floating point environment

    - by yCalleecharan
    Hi, I was looking at new features of C99 and saw the floating point environment: #include <fenv.h> My question is simple. If I'm performing floating point number computations, do I have to include the above preprocessor directive in my code? If no, then what does this directive do and when does it become important to include? Thanks a lot...

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  • good books on numerical computation with C

    - by yCalleecharan
    Hi, I've read the post "What is the best book on numerical methods?" and I wish to ask more or less the same question but in relation to C programming. Most of the time, C programming books on numerical methods are just another version of the author's previous Fortran book on the same subject. I've seen Applied numerical methods in C by Nakamura, Shoichiro and the C codes are not good programming practice. I've heard bad comments about Numerical Recipes by Press. Do you know good books on C that discusses numerical methods. It's seem better for me to ask about good books on C discussing numerical methods than rather asking books on numerical methods that discusses C. I've heard about Numerical Algorithms with C by Giesela Engeln-Müllges and A Numerical Library in C for Scientists and Engineers bu Lau but haven't read them. Good books will always have algorithms implemented in the programming language in a smart way. Thanks a lot...

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  • Coexisting installation of visual studio 2010 &2008

    - by yCalleecharan
    Hi, I currently have MVS2008 and I want to try the 2010 version hoping that it would compile C programs faster. I would like to know if I can have a 2008 installation coexisting with a 2010 installation on the same Windows partition, without conflicts in the Windows environment variables in Win XP. Thanks a lot...

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  • Information on Rojiani's Numerical methods C textbook

    - by yCalleecharan
    Hi, having taken a look at a few textbooks that discuss numerical methods and C programming, I was gladly surprised when browsing through "programming in C with numerical methods for engineers" by Rojiani. I understand of course it's important that one need to have a solid background in numerical methods prior to try implementing them on a computer. I would like to know if someone here has been using this book and if possible point out strengths and weaknesses of this textbook. Thanks a lot...

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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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  • calloc v/s malloc and time efficiency

    - by yCalleecharan
    Hi, I've read with interest the post "c difference between malloc and calloc". I'm using malloc in my code and would like to know what difference I'll have using calloc instead. My present (pseudo)code with malloc: Scenario 1 int main() { allocate large arrays with malloc INITIALIZE ALL ARRAY ELEMENTS TO ZERO for loop //say 1000 times do something and write results to arrays end for loop FREE ARRAYS with free command } //end main If I use calloc instead of malloc, then I'll have: Scenario2 int main() { for loop //say 1000 times ALLOCATION OF ARRAYS WITH CALLOC do something and write results to arrays FREE ARRAYS with free command end for loop } //end main I have three questions: Which of the scenarios is more efficient if the arrays are very large? Which of the scenarios will be more time efficient if the arrays are very large? In both scenarios,I'm just writing to arrays in the sense that for any given iteration in the for loop, I'm writing each array sequentially from the first element to the last element. The important question: If I'm using malloc as in scenario 1, then is it necessary that I initialize the elements to zero? Say with malloc I have array z = [garbage1, garbage2, garbage 3]. For each iteration, I'm writing elements sequentially i.e. in the first iteration I get z =[some_result, garbage2, garbage3], in the second iteration I get in the first iteration I get z =[some_result, another_result, garbage3] and so on, then do I need specifically to initialize my arrays after malloc?

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  • Ada: Adding an exception in a separate procedure when reading a file

    - by yCalleecharan
    This is a follow-up of this question: Ada: reading from a file . I would like to add an exception that checks if the file that I'm opening actually exists or not. I have made a separate procedure to avoid code clutter. Here is the main code test_read.adb: with Ada.Text_IO; use Ada.Text_IO; with Ada.Long_Float_Text_IO; with Ada.Float_Text_IO; procedure Test_Read is Input_File : File_Type; Value : Long_Float; procedure Open_Data (File : in Ada.Text_IO.File_Type; Name : in String) is separate; begin Ada.Text_IO.Open (File => Input_File, Mode => Ada.Text_IO.In_File, Name => "fx.txt"); while not End_Of_File (Input_File) loop Ada.Long_Float_Text_IO.Get (File => Input_File, Item => Value); Ada.Long_Float_Text_IO.Put (Item => value, Fore => 3, Aft => 5, Exp => 0); Ada.Text_IO.New_Line; end loop; Ada.Text_IO.Close (File => Input_File); end Test_Read; And here is the separate body test_read-open_data.adb of the procedure Open_Data: separate(test_read) procedure Open_Data (File : in Ada.Text_IO.File_Type; Name : in String) is --this procedure prepares a file for reading begin begin Ada.Text_IO.Open (File => File, Mode => Ada.Text_IO.In_File, Name => Name); exception when Ada.Text_IO.Name_Error => Ada.Text_IO.Put(File => Standard_Error, Item => "File not found."); end; end Open_Data; On compilation I get an error message in the separate body test_read-open_data.adb: actual for "File" must be a variable How to fix this? Thanks a lot...

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  • Visual studio 2010 exiting after program ends

    - by yCalleecharan
    Hi, I'm trying out Visual studio 2010 by compiling a C program. After it displays the solution in the "DOS" command window, the window is immediately closed. In Visual studio 2008, one gets the message press any key to continue and pressing a key closes the command prompt window. How do I set this behavior in 2010? Thanks a lot...

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  • C pointers and addresses

    - by yCalleecharan
    Hi, I always thought that *&p = p = &*p in C. I tried this code: #include <stdio.h> #include <stdlib.h> char a[] = "programming"; char *ap = &a[4]; int main(void) { printf("%x %x %x\n", ap, &*(ap), *&(ap)); /* line 13 */ printf("%x %x %x\n\n", ap+1, &*(ap+1), *&(ap+1)); /* line 14 */ } The first printf line (line 13) gives me the addresses: 40b0a8 40b0a8 40b0a8 which are the same as expected. But when I added the second printf line, Borland complains: "first.c": E2027 Must take address of a memory location in function main at line 14 I was expecting to get: 40b0a9 40b0a9 40b0a9. It seems that the expression *&(ap+1) on line 14 is the culprit here. I thought all three pointer expressions on line 14 are equivalent. Why am I thinking wrong? A second related question: The line char *ap = a; points to the first element of array a. I used char *ap = &a[4]; to point to the 5th element of array a. Is the expression char *ap = a; same as the expression char *ap = &a[0]; Is the last expression only more verbose than the previous one? Thanks a lot...

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  • C or Ada for engineering computations?

    - by yCalleecharan
    Hi,as an engineer I currently use C to write programs dealing with numerical methods. I like C as it's very fast. I don't want to move to C++ and I have been reading a bit about Ada which has some very good sides. I believe that much of the software in big industries have been or more correctly were written in Ada. I would like to know how C compares with Ada. Is Ada fast as C? I understand that no language is perfect but I would like to know if Ada was designed for scientific computing. Thanks a lot...

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  • Small eps figure size in Matlab

    - by yCalleecharan
    Hi, How to create a small eps file from a Matlab figure. I use LaTeX and the eps that I'm getting with Matlab (R2010a) is of the order 6 MB. How to set the plot options to give an eps figure of smaller size. Does the render options painters or zbuffer help? Thanks a lot...

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  • variable names in function definition, call and declaration

    - by yCalleecharan
    Hi, I see C books that use the same variable names in the function definition, calling function and declaration. Others use the same variable names in the calling function and in the declaration/prototype but a different one in the definition as in: void blabla(int something); //prototype blabla(something) // calling function inside main after something has been initialized to int void blabla(int something_else) //definition I have two questions: What convention is best to use in C?; Does the convention apply regardless whether a value is being passed "by-value" or if it's being passed by a pointer? Thanks a lot...

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  • correct format for function prototype

    - by yCalleecharan
    Hi, I'm writing to a text file using the following declaration: void create_out_file(char file_name[],long double *z1){ FILE *out; int i; if((out = fopen(file_name, "w+")) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < ARRAY_SIZE; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } Where z1 is an long double array of length ARRAY_SIZE. The calling function is: create_out_file("E:/first67/jz1.txt", z1); I defined the prototype as: void create_out_file(char file_name[], long double z1[]); which I'm putting before "int main" but after the preprocessor directives. My code works fine. I was thinking of putting the prototype as void create_out_file(char file_name[],long double *z1). Is this correct? *z1 will point to the first array element of z1. Is my declaration and prototype good programming practice? Thanks a lot...

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  • C precision of double: compiler dependent?

    - by yCalleecharan
    Hi,on my 32-bit machine (with an Intel T7700 duo core), I have 15 precision digits for both double and long double types for the C language. I compared the parameters LDBL_DIG for long doubles and DBL_DIG for doubles and they are both 15. I got these answers using MVS2008. I was wondering if these results can be compiler dependent or do they just depend on my processor? Thanks a lot...

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  • Release build in MVS 2010 professional v/s express for C

    - by yCalleecharan
    Hi, recently I discovered that "executing" a C program as a release build instead of a debug build optimizes the code and makes it run much faster. This is accessed through project properties configuration manager menu. I would like to know if this feature is the same in the professional version and the express edition of MVS 2010 in terms of speed optimization. I have the express edition. Also, I would like to know if C programs run with the same speed as in both the professional and express editions. I understand that the professional edition has many "software" tools for the serious programmer. Thanks a lot..

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  • Binary files printing and desired precision

    - by yCalleecharan
    Hi, I'm printing a variable say z1 which is a 1-D array containing floating point numbers to a text file so that I can import into Matlab or GNUPlot for plotting. I've heard that binary files (.dat) are smaller than .txt files. The definition that I currently use for printing to a .txt file is: void create_out_file(const char *file_name, const long double *z1, size_t z_size){ FILE *out; size_t i; if((out = _fsopen(file_name, "w+", _SH_DENYWR)) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < z_size; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } I have three questions: Are binary files really more compact than text files?; If yes, I would like to know how to modify the above code so that I can print the values of the array z1 to a binary file. I've read that fprintf has to be replaced with fwrite. My output file say dodo.dat should contain the values of array z1 with one floating number per line. I have %.16Le up in my code but I think that %.15Le is right as I have 15 precision digits with long double. I have put a dot (.) in the width position as I believe that this allows expansion to an arbitrary field to hold the desired number. Am I right? As an example with %.16Le, I can have an output like 1.0047914240730432e-002 which gives me 16 precision digits and the width of the field has the right width to display the number correctly. Is placing a dot (.) in the width position instead of a width value a good practice? Thanks a lot...

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  • memory problem with metapost

    - by yCalleecharan
    Hi, I'm using gnuplot to plot a graph to the mp format and then I'm converting it to eps via the command: mpost --sprologues=3 -soutputtemplate=\"%j-%c.eps\" myfigu.mp But I don't get the eps output; instead I get this message: This is MetaPost, version 1.208 (kpathsea version 3.5.7dev) (mem=mpost 2009.12.12) 6 MAY 2010 23:16 **myfigu.mp (./myfigu.mp ! MetaPost capacity exceeded, sorry [main memory size=3000000]. _wc-withpen .currentpen.withcolor.currentcolor gpdraw-...ptpath[(EXPR0)]_sms((EXPR1),(EXPR2))_wc .else:_ac.contour.ptpath[(... l.48052 gpdraw(0,517.1a,166.4b) ; If you really absolutely need more capacity, you can ask a wizard to enlarge me. How do I tweak in order to get more memory. The file from which I'm plotting has two columns of 189,200 values each. These values are of type long double (output from a C program). The text file containing these two column values is about 6 MB. Thanks a lot...

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  • time to run a program in C

    - by yCalleecharan
    Hi, I would like to know what lines of C code to add to a program so that it tells me the total time that the program takes to run. I guess there should be counter initialization near the beginning of main and one after the main function ends. Is the right header clock.h? Thanks a lot...

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  • Image processing on bifurcation diagram to get small eps size

    - by yCalleecharan
    Hello, I'm producing bifurcation diagrams (which are normally used in nonlinear dynamics). These diagrams identify abrupt changes in topologies due to stability changes. These abrupt changes occur as one or more parameters pass through some critical value(s). An example is here: http://en.wikipedia.org/wiki/File:LogisticMap_BifurcationDiagram.png On the above figure, some image processing has been done so as to make the plot more visually pleasant. A bifurcation diagram usually contains hundreds of thousands of points and the resulting eps file can become very big. Journal submission in the LaTeX format require that figures are to be submitted in the eps format. In my case one of such figures can result in about 6 MB in Matlab and even much more in Gnuplot. For the example in the above figure, 100,000 x values are calculated for each r and one can imagine that the resulting eps file would be huge. The site however explains some image processing that makes the plot more visually pleasing. Can anyone explain to me stepwise how go about? I can't understand the explanation provided in the "summary" section. Will the resulting image processing also reduce the figure size? Furthermore, any tips on reducing the file size of such a huge eps figure? Thanks a lot...

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  • double precision in Ada?

    - by yCalleecharan
    Hi, I'm very new to Ada and was trying to see if it offers double precision type. I see that we have float and Put( Integer'Image( Float'digits ) ); on my machine gives a value of 6, which is not enough for numerical computations. Does Ada has double and long double types as in C? Thanks a lot...

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  • resolution of an eps file

    - by yCalleecharan
    Hi, I'm using Gunplot to create a figure in the metapost format, after which I'm converting to eps via the command line: mpost --sprologues=3 -soutputtemplate=\"%j-%c.eps\" myfigu.mp to get myfigu-0.eps. I would like to know the resolution of such an eps file. How do I proceed? Is the eps thus created has a fixed resolution? Thanks a lot

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