What was I thinking? i. is much more prestigious than /:
x=: ?1e8$65536
y=: 0+x NB. avoid selfie optimizations. The effect is still
present, but less pronounced
x4=: 10 u:x
y4=: 10 u:y
x2=: 2 u:x4
y2=: 2 u:y4
timex'x i.y'
0.728156
timex'x4 i.y4'
3.8804
timex'x2 i.y2'
0.651964
Probably an oversight when 4-byte chars were added, on the theory that
2-byte chars would always get small-range optimization. (Which is, as a
matter of fact, not the case.)
Attached is a patch fixing the problem. This also helps with 4-column
matrices of 1-byte chars etc. (I think there may be reasonably cheap
gains to be made across the board for i. on matrices of few columns, but
at the very least small POT deserves to be fast.) This should also
improve performance for smaller 2-byte arrays that do not make the
small-range cut. With the patch:
timex'x4 i.y4'
0.613455
-E
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