Himanshu Jain on Mon, 07 Jan 2008 20:57:40 +0100 |
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Sparse matrices |
Hi all, I am working with large matrices >1000 * 1000 but with only a few non-zero entries in each row. Does PARI have any distinction between sparse and dense matrices. More specifically I want to compute the HNF of these matrices. The user guide mentions the use of hnfspec/hnfadd to reduce large sparse matrices. I looked at the code but could not understand it well enough to use it. Any tips on how hnfspec/hnfadd are to be used. Another doubt: Given a matrix M whose rank is equal to the number of columns (for example mathnf returns such matrices). I want to extract an invertible matrix from M say M' and compute the inverse of M'. I also need to know which rows were extracted from M to get M'. I first use indexrank to get M' and then gdiv to get inverse(M'). Is this the most efficient way? Thanks a lot, Himanshu