C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  large and sparse matrices          C++Talk.NET Forum Index -> C Language View previous topic :: View next topic   Author Message mediratta@gmail.com Guest Posted: Fri May 11, 2007 9:12 am    Post subject: large and sparse matrices Hi, I want to allocate memory for a large matrix, whose size will be around 2.5 million x 17000. Three fourth of its rows will have all zeroes, but it is not known which will be those rows. If I try to allocate memory for this huge array, then I get a segmentation fault saying: Program received signal SIGSEGV, Segmentation fault. 0xb7dd5226 in mallopt () from /lib/tls/i686/cmov/libc.so.6 I have not given any compiler options. I think that the error is because I am allocating too big a size ? Can anyone please, suggest me how to store/manage such a matrix in C/C+ + ? Can mmap be useful ? I am using linux on i386 with gcc (GCC) 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5) thanks anupam Back to top jacob navia Guest Posted: Fri May 11, 2007 9:12 am    Post subject: Re: large and sparse matrices mediratta (AT) gmail (DOT) com a écrit : Quote: Hi, I want to allocate memory for a large matrix, whose size will be around 2.5 million x 17000. Three fourth of its rows will have all zeroes, but it is not known which will be those rows. If I try to allocate memory for this huge array, then I get a segmentation fault saying: Program received signal SIGSEGV, Segmentation fault. 0xb7dd5226 in mallopt () from /lib/tls/i686/cmov/libc.so.6 I have not given any compiler options. I think that the error is because I am allocating too big a size ? Can anyone please, suggest me how to store/manage such a matrix in C/C+ + ? Can mmap be useful ? I am using linux on i386 with gcc (GCC) 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5) thanks anupam You want memory of 2 500 000 * 17 000 * sizeof(double). This is 340 000 000 000 bytes, around 316.6 GB. Even if you do not use double but just a char for your data you need more than 42 GB. There are several alternatives. For instance, typedef struct matRow { int index; // 0 to 2 500 000 struct matRow *NextRow; // Pointer to next row double data[17000]; } MATROW; Then, you store just the rows with some data in it. When you want to index the matrix, if the row is not in the list of rows the dta is zero. Of course this is naive and very inefficient. This is just the idea. To see more advanced sparse matrix software google for "sparse matrix implementation" or similar. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C Language All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.