hi all, I contributed a toy implementation of block sparse matrices to the linear-algebra package (also attached). This is probably not meant for serious business, as all the code is m-files only, but is rather a demonstration of what can now be done in Octave.
Basic operations (+, -, *, ', .') are supported. No division, of course. Curiously enough, despite the m-file implementation, already for a 1000x1000 matrix with 10x10 blocks and 4 blocks per row (corresponds to a FE matrix of 1000-element conforming triangular grid with 3-rd order discontinuous polynomial elements), this toy implementation can outperform the built-in sparse matrices: nb = 10; n = 1000; nrhs = 1; [i, j] = find (sprand (n, n, 3/n) + speye (n)); a = rand (nb, nb, length (i)); s = blksparse (i, j, a, n, n); v = rand (nb*n, nrhs); tic; for it = 1:100/nrhs s * v; endfor toc s = sparse (s); tic; for it = 1:100/nrhs s * v; endfor toc On my computer (Core 2 Duo, g++ -O3 -march=native), I get: octave:1> ttbs Elapsed time is 0.180152 seconds. Elapsed time is 0.344266 seconds. with nrhs=10 (thus reducing interpreter overhead and improving cache locality for blksparse), it gets even better: octave:3> ttbs Elapsed time is 0.0802341 seconds. Elapsed time is 0.34509 seconds. Of course, as division is unsupported, the usefulness of this implementation is quite limited, but still it can be used e.g. for iterative solvers. Comments? Suggestions? Note that this code requires Octave tip as it relies on certain recent additions (blkmm, accumdim). -- RNDr. Jaroslav Hajek, PhD computing expert & GNU Octave developer Aeronautical Research and Test Institute (VZLU) Prague, Czech Republic url: www.highegg.matfyz.cz
blksparse.tgz
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