29 lines
670 B
Zig
29 lines
670 B
Zig
const math = @import("index.zig");
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pub fn expo2(x: var) -> @typeOf(x) {
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const T = @typeOf(x);
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switch (T) {
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f32 => expo2f(x),
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f64 => expo2d(x),
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else => @compileError("expo2 not implemented for " ++ @typeName(T)),
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}
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}
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fn expo2f(x: f32) -> f32 {
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const k: u32 = 235;
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const kln2 = 0x1.45C778p+7;
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const u = (0x7F + k / 2) << 23;
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const scale = @bitCast(f32, u);
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math.exp(x - kln2) * scale * scale
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}
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fn expo2d(x: f64) -> f64 {
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const k: u32 = 2043;
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const kln2 = 0x1.62066151ADD8BP+10;
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const u = (0x3FF + k / 2) << 20;
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const scale = @bitCast(f64, u64(u) << 32);
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math.exp(x - kln2) * scale * scale
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}
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