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+ on Sparse Arguments Improved |
initial writing: 2001-08-02 |
The dyad + (and other atomic functions such as - * )
on sparse arguments are now more efficient in time and space. For example:
s=: 13 17 19 x=: ?.1600$1e6 i=: ?.(1600,#s)$s p=: (800{.x) (<"1 ]800{.i)}1$.s q=: (800}.x) (<"1 ]800}.i)}1$.s ts=: 6!:2 , 7!:2@] NB. time and space ts 'p+q'
Expression | J 5.01 | J 4.06 | Ratio | ||||||||
p + q | 0.000450895 | 33792 | 0.001660546 | 153856 | 3.68 | 4.55 | |||||
p - q | 0.000447822 | 33792 | 0.001658311 | 153856 | 3.70 | 4.55 | |||||
p * q | 0.000249473 | 5248 | 0.000749537 | 52608 | 3.00 | 10.02 | |||||
p % q | 0.000645613 | 33792 | 0.001753016 | 153856 | 2.72 | 4.55 | |||||
p = q | 0.000742552 | 19456 | 0.001741841 | 127232 | 2.35 | 6.54 | |||||
p ~:q | 0.000748978 | 19456 | 0.001632051 | 127232 | 2.18 | 6.54 | |||||
p < q | 0.000670756 | 19456 | 0.001730108 | 136448 | 2.58 | 7.01 |