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vm: a bit faster not to trim on each iteration...

db4
John Benediktsson 2012-08-04 09:13:05 -07:00
parent f7bb7c6a32
commit 61a6b5692f
1 changed files with 30 additions and 16 deletions
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46
vm/bignum.cpp
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@ -1772,7 +1772,8 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
bignum_twodigit_type x, y, q, s, t, A, B, C, D; bignum_twodigit_type x, y, q, s, t, A, B, C, D;
int nbits, k; int nbits, k;
bignum_length_type size_a, size_b, size_c; bignum_length_type size_a, size_b, size_c;
bignum_digit_type *scan_a, *scan_b, *scan_c, *scan_d, *a_end, *b_end; bignum_digit_type *scan_a, *scan_b, *scan_c, *scan_d;
bignum_digit_type *a_end, *b_end, *c_end;
/* clone the bignums so we can modify them in-place */ /* clone the bignums so we can modify them in-place */
scan_a = BIGNUM_START_PTR (a); scan_a = BIGNUM_START_PTR (a);
@ -1838,15 +1839,32 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
if (size_b == 0) { if (size_b == 0) {
return a; return a;
} }
e = bignum_remainder (a, b); e = bignum_trim (a);
GC_BIGNUM (e); GC_BIGNUM(e);
if (e == BIGNUM_OUT_OF_BAND) { f = bignum_trim (b);
return e; GC_BIGNUM(f);
c = bignum_remainder (e, f);
GC_BIGNUM (c);
if (c == BIGNUM_OUT_OF_BAND) {
return c;
} }
a = b;
// copy 'b' to 'a'
scan_a = BIGNUM_START_PTR (a);
scan_b = BIGNUM_START_PTR (b);
b_end = scan_b + size_b;
while (scan_b < b_end) *(scan_a++) = *(scan_b++);
size_a = size_b; size_a = size_b;
b = e;
size_b = BIGNUM_LENGTH (e); // copy 'c' to 'b'
scan_b = BIGNUM_START_PTR (b);
scan_c = BIGNUM_START_PTR (c);
size_c = BIGNUM_LENGTH (c);
BIGNUM_ASSERT (size_c <= size_b);
c_end = scan_c + size_c;
while (scan_c < c_end) *(scan_b++) = *(scan_c++);
size_b = size_c;
continue; continue;
} }
@ -1901,14 +1919,10 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
BIGNUM_ASSERT (s == 0); BIGNUM_ASSERT (s == 0);
BIGNUM_ASSERT (t == 0); BIGNUM_ASSERT (t == 0);
e = bignum_trim (a); // update size_a and size_b to remove any zeros at end
GC_BIGNUM(e); while (size_a > 0 && *(--scan_a) == 0) size_a--;
a = e; while (size_b > 0 && *(--scan_b) == 0) size_b--;
size_a = BIGNUM_LENGTH (a);
f = bignum_trim (b);
GC_BIGNUM(f);
b = f;
size_b = BIGNUM_LENGTH (b);
BIGNUM_ASSERT (size_a >= size_b); BIGNUM_ASSERT (size_a >= size_b);
} }