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big: Fix sqrt, div, add with certain inputs.

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This commit is contained in:
Jeroen van Rijn
2021-08-11 20:59:52 +02:00
parent 7afd1b15a8
commit 149c7b88df
7 changed files with 455 additions and 122 deletions
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core/math/big/basic.odin
+13 -17
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@@ -359,7 +359,7 @@ int_halve :: proc(dest, src: ^Int) -> (err: Error) {
*/
fwd_carry := DIGIT(0);
for x := dest.used; x >= 0; x -= 1 {
for x := dest.used - 1; x >= 0; x -= 1 {
/*
Get the carry for the next iteration.
*/
@@ -761,21 +761,16 @@ sqrmod :: proc { int_sqrmod, };
*/
_int_add :: proc(dest, a, b: ^Int) -> (err: Error) {
dest := dest; x := a; y := b;
if err = clear_if_uninitialized(x); err != .None {
return err;
}
if err = clear_if_uninitialized(y); err != .None {
return err;
}
old_used, min_used, max_used, i: int;
if x.used < y.used {
x, y = y, x;
assert(x.used >= y.used);
}
min_used = x.used;
max_used = y.used;
min_used = y.used;
max_used = x.used;
old_used = dest.used;
if err = grow(dest, max(max_used + 1, _DEFAULT_DIGIT_COUNT)); err != .None {
@@ -827,7 +822,6 @@ _int_add :: proc(dest, a, b: ^Int) -> (err: Error) {
Add remaining carry.
*/
dest.digit[i] = carry;
zero_count := old_used - dest.used;
/*
Zero remainder.
@@ -1111,6 +1105,7 @@ _int_div_3 :: proc(quotient, numerator: ^Int) -> (remainder: int, err: Error) {
_int_div_small :: proc(quotient, remainder, numerator, denominator: ^Int) -> (err: Error) {
ta, tb, tq, q := &Int{}, &Int{}, &Int{}, &Int{};
c: int;
goto_end: for {
if err = one(tq); err != .None { break goto_end; }
@@ -1121,20 +1116,21 @@ _int_div_small :: proc(quotient, remainder, numerator, denominator: ^Int) -> (er
if err = abs(ta, numerator); err != .None { break goto_end; }
if err = abs(tb, denominator); err != .None { break goto_end; }
if err = shl(tb, tb, n); err != .None { break goto_end; }
if err = shl(tq, tq, n); err != .None { break goto_end; }
for ; n >= 0; n -= 1 {
c: int;
if c, err = cmp(tb, ta); err != .None { break goto_end; }
if c != 1 {
for n >= 0 {
if c, _ = cmp_mag(ta, tb); c == 0 || c == 1 {
// ta -= tb
if err = sub(ta, ta, tb); err != .None { break goto_end; }
if err = add( q, tq, q); err != .None { break goto_end; }
// q += tq
if err = add( q, q, tq); err != .None { break goto_end; }
}
if err = shr1(tb, tb); err != .None { break goto_end; }
if err = shr1(tq, tq); err != .None { break goto_end; }
}
n -= 1;
}
/*
Now q == quotient and ta == remainder.