June 5, 2000
1:22 p.m.
Paul Gettings writes:
However, the matrix is empty except for the main diagonal. Multiplying by a diagonalized matrix is just vectorized multiplication: a 0 0 0 b 0 . <x, y, z> = <az, by, cz> 0 0 c My mistake - I need to multiply the 7731x7731 by a 7731x220 element matrix - square matrix times rectangular matrix, not just 2 diagonal matrices. Otherwise, the problem wouldn't be so hard. :)
Still it's not so bad, you just need to break the 7731x220 matrix into 220 vectors of length 7731 and multiply each of them by the diagonal "matrix", one at a time, and glue the results back together. The 7731x220 matrix should weigh in at about 6MB, hopefully you have enough memory for this...