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https://github.com/ziglang/zig.git
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dc62dde982
This is to account for the small differences in math functions of different libcs. For example, if the compiler links against glibc, but the target is musl libc, then these values might be slightly different. Arguably, this is a bug in the compiler because comptime should emulate the target, including rounding errors in libc math functions. However that behavior is not what this particular test is intended to cover.
76 lines
2.2 KiB
Zig
76 lines
2.2 KiB
Zig
const std = @import("std");
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const Random = std.rand.Random;
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const ZigTable = struct {
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r: f64,
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x: [257]f64,
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f: [257]f64,
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pdf: fn (f64) f64,
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is_symmetric: bool,
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zero_case: fn (*Random, f64) f64,
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};
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fn ZigTableGen(comptime is_symmetric: bool, comptime r: f64, comptime v: f64, comptime f: fn (f64) f64, comptime f_inv: fn (f64) f64, comptime zero_case: fn (*Random, f64) f64) ZigTable {
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var tables: ZigTable = undefined;
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tables.is_symmetric = is_symmetric;
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tables.r = r;
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tables.pdf = f;
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tables.zero_case = zero_case;
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tables.x[0] = v / f(r);
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tables.x[1] = r;
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for (tables.x[2..256]) |*entry, i| {
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const last = tables.x[2 + i - 1];
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entry.* = f_inv(v / last + f(last));
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}
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tables.x[256] = 0;
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for (tables.f[0..]) |*entry, i| {
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entry.* = f(tables.x[i]);
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}
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return tables;
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}
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const norm_r = 3.6541528853610088;
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const norm_v = 0.00492867323399;
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fn norm_f(x: f64) f64 {
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return @exp(-x * x / 2.0);
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}
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fn norm_f_inv(y: f64) f64 {
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return @sqrt(-2.0 * @log(y));
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}
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fn norm_zero_case(random: *Random, u: f64) f64 {
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_ = random;
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_ = u;
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return 0.0;
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}
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const NormalDist = blk: {
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@setEvalBranchQuota(30000);
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break :blk ZigTableGen(true, norm_r, norm_v, norm_f, norm_f_inv, norm_zero_case);
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};
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test "bug 920 fixed" {
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if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest; // TODO
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const NormalDist1 = blk: {
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break :blk ZigTableGen(true, norm_r, norm_v, norm_f, norm_f_inv, norm_zero_case);
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};
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for (NormalDist1.f) |_, i| {
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// Here we use `expectApproxEqAbs` instead of `expectEqual` to account for the small
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// differences in math functions of different libcs. For example, if the compiler
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// links against glibc, but the target is musl libc, then these values might be
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// slightly different.
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// Arguably, this is a bug in the compiler because comptime should emulate the target,
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// including rounding errors in libc math functions. However that behavior is not
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// what this particular test is intended to cover.
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try std.testing.expectApproxEqAbs(NormalDist1.f[i], NormalDist.f[i], @sqrt(std.math.floatEps(f64)));
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}
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}
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