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u&.(a.&i.) Improved |
initial writing: 2007-10-17 |
The phrase u&.(a.&i.) (also u&.(a.i.])) have been made more efficient in the following cases:
| Case | Requirements | ||
| monad | (u-:u"0) y | ||
| monad | u is m b./ | where m e. 16+i.16 | |
| dyad | u is m b. | where m e. 16+i.16 | |
The m b. cases provide bitwise functions on character arguments. Note that the requirement u-:u"0 does not imply that the rank of u must be 0.
The following benchmarks demonstrate the improvement.
x=: a. {~ 1e6 ?@$ 256
y=: a. {~ 1e6 ?@$ 256
c=: a. {~ ?256
ts=: 6!:2 , 7!:2@] NB. time and space
ts 'Expression'
| Expression | J 6.02 | J 6.01 | Ratio | |||||||||
| (256|>:)&.(a.&i.) y | 0.004724 | 1.06458e6 | 0.050507 | 1.25868e7 | 10.69 | 11.82 | ||||||
| 123&(22 b.)&.(a.&i.) y | 0.001583 | 1.06470e6 | 0.030874 | 9.44115e6 | 19.51 | 8.87 | ||||||
| x 22 b.&.(a.&i.) y | 0.002221 | 1.05197e6 | 0.043039 | 1.25867e7 | 19.38 | 11.96 | ||||||
| c 22 b.&.(a.&i.) y | 0.001419 | 1.05216e6 | 0.030395 | 9.44102e6 | 21.43 | 8.97 | ||||||
| 25 b./&.(a.i.]) y | 0.000529 | 1.66400e3 | 0.007741 | 4.20090e6 | 14.63 | 2524.58 | ||||||