021d50405
Denys Vlasenko
2017-04-13
Subject
factor: improve comments for sieving logic
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coreutils/factor.c+6 -2
| @@ -73,7 +73,7 @@ static NOINLINE void factorize(wide_t N) | |
| MULTIPLE_OF_3 = 1 << 2, | |
| MULTIPLE_OF_5 = 1 << 6, | |
| MULTIPLE_OF_7 = 1 << 11, | |
| - | MULTIPLE_3_5_7 = MULTIPLE_OF_3 | MULTIPLE_OF_5 | MULTIPLE_OF_7, |
| + | MULTIPLE_DETECTED = MULTIPLE_OF_3 | MULTIPLE_OF_5 | MULTIPLE_OF_7, |
| }; | |
| unsigned sieve_word; | |
| @@ -102,9 +102,13 @@ static NOINLINE void factorize(wide_t N) | |
| // count5 = 6; | |
| // count7 = 9; | |
| sieve_word = 0 | |
| + | /* initial count for SHIFT_n is (n-1)/2*3: */ |
| + (MULTIPLE_OF_3 - 3 * SHIFT_3) | |
| + (MULTIPLE_OF_5 - 6 * SHIFT_5) | |
| + (MULTIPLE_OF_7 - 9 * SHIFT_7) | |
| + | //+ (MULTIPLE_OF_11 - 15 * SHIFT_11) |
| + | //+ (MULTIPLE_OF_11 - 18 * SHIFT_13) |
| + | //+ (MULTIPLE_OF_11 - 24 * SHIFT_17) |
| ; | |
| factor = 3; | |
| for (;;) { | |
| @@ -133,7 +137,7 @@ static NOINLINE void factorize(wide_t N) | |
| // if (count3 && count5 && count7) | |
| // continue; | |
| sieve_word += INCREMENT_EACH; | |
| - | if (!(sieve_word & MULTIPLE_3_5_7)) |
| + | if (!(sieve_word & MULTIPLE_DETECTED)) |
| continue; | |
| /* | |
| * "factor" is multiple of 3 33% of the time (count3 reached 0), | |