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-/ .* Improved

last updated: 2000-06-30


The monad -/ . * (determinant) on square matrices is now implemented by Gaussian elimination with full pivoting. (Previously, it used the general code for u . v that worked for all verbs.) The result is improved efficiency in time and space, as the following comparisons illustrate:

   ts=: 6!:2 , 7!:2@]
   x=: 0.01 * _5e4+?(n,n)$1e5
   ts '-/ .* x'
n             J 4.05       J 4.04
1 0.000155048 6720       0.000150857 6784
2 0.000163429 6912 0.000163429 6976
3 0.000150857 6720 0.000236343 9024
4 0.000153371 6848 0.000542248 16384
5 0.000155048 6848 0.00213714 25472
6 0.000190248 7104 0.0120828 43328
7 0.000165943 7104 0.0837802 80448
8 0.000175162 7616 0.66968 151936
9 0.000183543 7616 6.08026 239872
10 0.000196114 7616 60.9625 410304



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