If we have a square, the speedup can be extremely large
(in best case example below, it's ~40000 times faster):
$ time ./busybox_old factor 18446743988964486098
18446743988964486098: 2 3037000493 3037000493
real 0m4.246s
$ time ./busybox factor 18446743988964486098
18446743988964486098: 2 3037000493 3037000493
real 0m0.000s
function old new delta
isqrt_odd - 57 +57
print_w - 36 +36
factorize 218 236 +18
print_h - 7 +7
factorize_numstr 65 72 +7
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(add/remove: 3/0 grow/shrink: 2/0 up/down: 125/0) Total: 125 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
thus far only able to factor up to ULLONG_MAX
function old new delta
factor_main - 378 +378
packed_usage 31427 31502 +75
applet_names 2590 2597 +7
applet_main 1500 1504 +4
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(add/remove: 2/0 grow/shrink: 3/0 up/down: 464/0) Total: 464 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
