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big: Improve timing code.

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This commit is contained in:
Jeroen van Rijn
2021-08-11 20:59:53 +02:00
parent 35d8976de4
commit 511057ca36
2 changed files with 53 additions and 48 deletions
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core/math/big/helpers.odin
+11 -26
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@@ -205,19 +205,19 @@ int_bitfield_extract :: proc(a: ^Int, offset, count: int) -> (res: _WORD, err: E
*/
if count == 1 {
limb := offset / _DIGIT_BITS;
if limb < 0 || limb >= a.used { return 0, .Invalid_Argument; }
if limb < 0 || limb >= a.used { return 0, .Invalid_Argument; }
i := _WORD(1 << _WORD((offset % _DIGIT_BITS)));
return 1 if ((_WORD(a.digit[limb]) & i) != 0) else 0, nil;
}
if count > _WORD_BITS || count < 1 { return 0, .Invalid_Argument; }
if count > _WORD_BITS || count < 1 { return 0, .Invalid_Argument; }
/*
There are 3 possible cases.
- [offset:][:count] covers 1 DIGIT,
e.g. offset: 0, count: 60 = bits 0..59
e.g. offset: 0, count: 60 = bits 0..59
- [offset:][:count] covers 2 DIGITS,
e.g. offset: 5, count: 60 = bits 5..59, 0..4
e.g. offset: 5, count: 60 = bits 5..59, 0..4
e.g. offset: 0, count: 120 = bits 0..59, 60..119
- [offset:][:count] covers 3 DIGITS,
e.g. offset: 40, count: 100 = bits 40..59, 0..59, 0..19
@@ -230,41 +230,26 @@ int_bitfield_extract :: proc(a: ^Int, offset, count: int) -> (res: _WORD, err: E
num_bits := min(bits_left, _DIGIT_BITS - bits_offset);
// fmt.printf("offset: %v | count: %v\n\n", offset, count);
// fmt.printf("left: %v | bits_offset: %v | limb: %v | num: %v\n\n", bits_left, bits_offset, limb, num_bits);
shift := offset % _DIGIT_BITS;
mask := (_WORD(1) << uint(num_bits)) - 1;
// fmt.printf("shift: %v | mask: %v\n", shift, mask);
// fmt.printf("d: %v\n", a.digit[limb]);
res = (_WORD(a.digit[limb]) >> uint(shift)) & mask;
// fmt.printf("res: %v\n", res);
shift := offset % _DIGIT_BITS;
mask := (_WORD(1) << uint(num_bits)) - 1;
res = (_WORD(a.digit[limb]) >> uint(shift)) & mask;
bits_left -= num_bits;
if bits_left == 0 { return res, nil; }
res_shift := num_bits;
num_bits = min(bits_left, _DIGIT_BITS);
mask = (1 << uint(num_bits)) - 1;
num_bits = min(bits_left, _DIGIT_BITS);
mask = (1 << uint(num_bits)) - 1;
v := (_WORD(a.digit[limb + 1]) & mask) << uint(res_shift);
res |= v;
res |= (_WORD(a.digit[limb + 1]) & mask) << uint(res_shift);
bits_left -= num_bits;
if bits_left == 0 { return res, nil; }
// fmt.printf("bits_left: %v | offset: %v | num: %v\n", bits_left, offset, num_bits);
mask = (1 << uint(bits_left)) - 1;
res_shift += _DIGIT_BITS;
v = (_WORD(a.digit[limb + 2]) & mask) << uint(res_shift);
res |= v;
res |= (_WORD(a.digit[limb + 2]) & mask) << uint(res_shift);
return res, nil;
}