Commit ee47643b6eb175f4414a50c19afa0c22b2d15949 | zig

Signed-off-by: tison <wander4096@gmail.com>

2 files changed, 21 insertions(+), 2 deletions(-)

lib/std/math/big/int.zig+2-2

...	...	@@ -69,7 +69,7 @@ pub fn calcPowLimbsBufferLen(a_bit_count: usize, y: usize) usize {
69	69	pub fn calcSqrtLimbsBufferLen(a_bit_count: usize) usize {
70	70	const a_limb_count = (a_bit_count - 1) / limb_bits + 1;
71	71	const shift = (a_bit_count + 1) / 2;
72		const u_s_rem_limb_count = 1 + ((shift - 1) / limb_bits + 1);
	72	const u_s_rem_limb_count = 1 + ((shift / limb_bits) + 1);
73	73	return a_limb_count + 3 * u_s_rem_limb_count + calcDivLimbsBufferLen(a_limb_count, u_s_rem_limb_count);
74	74	}
75	75
...	...	@@ -1380,7 +1380,7 @@ pub const Mutable = struct {
1380	1380	var u = b: {
1381	1381	const start = buf_index;
1382	1382	const shift = (a.bitCountAbs() + 1) / 2;
1383		buf_index += 1 + ((shift - 1) / limb_bits + 1);
	1383	buf_index += 1 + ((shift / limb_bits) + 1);
1384	1384	var m = Mutable.init(limbs_buffer[start..buf_index], 1);
1385	1385	m.shiftLeft(m.toConst(), shift); // u must be >= ⌊√a⌋, and should be as small as possible for efficiency
1386	1386	break :b m;

lib/std/math/big/int_test.zig+19

...	...	@@ -3161,6 +3161,7 @@ test "big.int.Managed sqrt(0) = 0" {
3161	3161	try a.setString(10, "0");
3162	3162
3163	3163	try res.sqrt(&a);
	3164	try testing.expectEqual(@as(i32, 0), try res.to(i32));
3164	3165	}
3165	3166
3166	3167	test "big.int.Managed sqrt(-1) = error" {
...	...	@@ -3175,3 +3176,21 @@ test "big.int.Managed sqrt(-1) = error" {
3175	3176
3176	3177	try testing.expectError(error.SqrtOfNegativeNumber, res.sqrt(&a));
3177	3178	}
	3179
	3180	test "big.int.Managed sqrt(n) succeed with res.bitCountAbs() >= usize bits" {
	3181	const allocator = testing.allocator;
	3182	var a = try Managed.initSet(allocator, 1);
	3183	defer a.deinit();
	3184
	3185	var res = try Managed.initSet(allocator, 1);
	3186	defer res.deinit();
	3187
	3188	// a.bitCountAbs() = 127 so the first attempt has 64 bits >= usize bits
	3189	try a.setString(10, "136036462105870278006290938611834481486");
	3190	try res.sqrt(&a);
	3191
	3192	var expected = try Managed.initSet(allocator, 1);
	3193	defer expected.deinit();
	3194	try expected.setString(10, "11663466984815033033");
	3195	try std.testing.expectEqual(std.math.Order.eq, expected.order(res));
	3196	}