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std.math.asinh: fixed -0.0 evaluating to 0.0

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Ruben Dimas 2023-09-12 02:19:21 -04:00 committed by Marc Tiehuis
parent 7827265ea8
commit a8a4f1755e
1 changed files with 10 additions and 19 deletions
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29
lib/std/math/asinh.zig
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@ -28,30 +28,25 @@ pub fn asinh(x: anytype) @TypeOf(x) {
fn asinh32(x: f32) f32 {
const u = @as(u32, @bitCast(x));
const i = u & 0x7FFFFFFF;
const s = i >> 31;
const s = u >> 31;
var rx = @as(f32, @bitCast(i)); // |x|
// TODO: Shouldn't need this explicit check.
if (math.isNegativeInf(x)) {
return x;
}
// |x| >= 0x1p12 or inf or nan
if (i >= 0x3F800000 + (12 << 23)) {
rx = @log(rx) + 0.69314718055994530941723212145817656;
}
// |x| >= 2
else if (i >= 0x3F800000 + (1 << 23)) {
rx = @log(2 * x + 1 / (@sqrt(x * x + 1) + x));
rx = @log(2 * rx + 1 / (@sqrt(rx * rx + 1) + rx));
}
// |x| >= 0x1p-12, up to 1.6ulp error
else if (i >= 0x3F800000 - (12 << 23)) {
rx = math.log1p(x + x * x / (@sqrt(x * x + 1) + 1));
rx = math.log1p(rx + rx * rx / (@sqrt(rx * rx + 1) + 1));
}
// |x| < 0x1p-12, inexact if x != 0
else {
math.doNotOptimizeAway(x + 0x1.0p120);
math.doNotOptimizeAway(rx + 0x1.0p120);
}
return if (s != 0) -rx else rx;
@ -60,29 +55,25 @@ fn asinh32(x: f32) f32 {
fn asinh64(x: f64) f64 {
const u = @as(u64, @bitCast(x));
const e = (u >> 52) & 0x7FF;
const s = e >> 63;
const s = u >> 63;
var rx = @as(f64, @bitCast(u & (maxInt(u64) >> 1))); // |x|
if (math.isNegativeInf(x)) {
return x;
}
// |x| >= 0x1p26 or inf or nan
if (e >= 0x3FF + 26) {
rx = @log(rx) + 0.693147180559945309417232121458176568;
}
// |x| >= 2
else if (e >= 0x3FF + 1) {
rx = @log(2 * x + 1 / (@sqrt(x * x + 1) + x));
rx = @log(2 * rx + 1 / (@sqrt(rx * rx + 1) + rx));
}
// |x| >= 0x1p-12, up to 1.6ulp error
else if (e >= 0x3FF - 26) {
rx = math.log1p(x + x * x / (@sqrt(x * x + 1) + 1));
rx = math.log1p(rx + rx * rx / (@sqrt(rx * rx + 1) + 1));
}
// |x| < 0x1p-12, inexact if x != 0
else {
math.doNotOptimizeAway(x + 0x1.0p120);
math.doNotOptimizeAway(rx + 0x1.0p120);
}
return if (s != 0) -rx else rx;
@ -121,7 +112,7 @@ test "math.asinh64" {
test "math.asinh32.special" {
try expect(asinh32(0.0) == 0.0);
try expect(asinh32(-0.0) == -0.0);
try expect(@as(u32, @bitCast(asinh32(-0.0))) == @as(u32, 2147483648));
try expect(math.isPositiveInf(asinh32(math.inf(f32))));
try expect(math.isNegativeInf(asinh32(-math.inf(f32))));
try expect(math.isNan(asinh32(math.nan(f32))));
@ -129,7 +120,7 @@ test "math.asinh32.special" {
test "math.asinh64.special" {
try expect(asinh64(0.0) == 0.0);
try expect(asinh64(-0.0) == -0.0);
try expect(@as(u64, @bitCast(asinh64(-0.0))) == @as(u64, 9223372036854775808));
try expect(math.isPositiveInf(asinh64(math.inf(f64))));
try expect(math.isNegativeInf(asinh64(-math.inf(f64))));
try expect(math.isNan(asinh64(math.nan(f64))));