Hi Germán, You could be suffering from memory allocation costs, not so much the operations themselves. The rmtxop program uses doubles and 3 components per matrix entry, so that's (3x2048x2305 x 8 bytes) or 108 MBytes for each of your matrices. When you multiply one such matrix by a sky vector, you only have the additional memory needed by the vector (54 KBytes). When you add matrices, rmtxop keeps two of them in memory at a time, or 216 MBytes of memory. That's not a lot for most PCs these days, but the allocation and freeing of that much space may take some time if malloc is not efficient.
I should have asked if your matrices are stored as binary data. If they are ASCII (text), then for sure the strtod()/atof() calls will dominate calculation time completely. Switching to a binary double matrix representation would be faster and a better measure of the time these operations actually take. You would probably need to profile your code to get a clear idea of where it's spending its time. Cheers, -Greg P.S. The dctimestep uses floats instead of doubles, so takes half the memory. It's also optimized for matrix multiplications where there are zero rows or columns, so it's substantially faster for annual sky matrix calculations. > From: Germán Molina Larrain <germoli...@gmail.com> > Date: May 10, 2017 9:19:17 AM PDT > > Hello All, > > Thanks Douglas... I have not idea, really, how it is done internally. I do > not really mind this 'bug', but maybe something could be done to mke it > better??. > > Greg, > > the sky vector is MF4 (2305x1); the DC matrices are all (2048x2305). What I > was doing before was: > > Results = DC1*sky + DC2*sky + DC3*sky + DC3*sky > rmtxop DC1 sky_vec > lux1 > rmtxop DC2 sky_vec > lux2 > rmtxop DC3 sky_vec > lux3 > rmtxop DC4 sky_vec > lux4 > > rmtxop lux1 + lux2 + lux3 + lux4 > total_lux > > > > Results = (DC1+DC2+DC3+DC4)*sky > rmtxop DC1 + DC2 + DC3 + DC4 > TotalDC > rmtxop TotalDC sky_vec > total_lux > > When replacing, on the first case, rmtxop by dctimestep I got slightly faster > results. > > Best, > > Germán > > 2017-05-10 13:09 GMT-03:00 Gregory J. Ward <gregoryjw...@gmail.com>: > Can you reduce this to the actual commands, noting the matrix dimensions for > us? > > Thanks! > -Greg > >> From: Germán Molina Larrain <germoli...@gmail.com> >> Date: May 10, 2017 5:52:47 AM PDT >> >> Hello all, >> >> I am working on a research project that requires a lot of matrix matrix >> operations (i.e. add, multiply, substract). Since I am working with the >> ouptuts of RFLUXMTX, I am using RMTXOP. >> >> Since I have to do this lots of times, I designed my scripts so they are >> efficient. Accordingly, avoiding matrix multiplication was a priority... so >> I rearranged the equation: >> >> Results = DC1*sky + DC2*sky + DC3*sky + DC3*sky >> >> into >> >> Results = (DC1+DC2+DC3+DC4)*sky >> >> I thought the latter one would be much faster... but it takes double the >> time! Is there any reason for that? I am somehow surprised since, I >> understand, matrix multiplication is a O(n^3) algorithm while adding is a >> O(n^2) one. >> >> The DC matrices are the contribution from different windows to the workplane >> (using the 3-phase method... VTD) and the sky is a vector, not a matrix. >> >> Best, >> >> Germán > > _______________________________________________ > Radiance-dev mailing list > Radiance-dev@radiance-online.org > https://www.radiance-online.org/mailman/listinfo/radiance-dev > > > _______________________________________________ > Radiance-dev mailing list > Radiance-dev@radiance-online.org > https://www.radiance-online.org/mailman/listinfo/radiance-dev
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