35 lines
1.2 KiB
Go
35 lines
1.2 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: MIT
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package core
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import "testing"
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// TestWhereHalfCanonicalisesNaN pins the float16 fast path of Where:
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// every selected half value narrows through HalfFromFloat64 on the way
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// out, so a NaN loses its payload and lands as the canonical 0x7E00 with
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// its sign kept, while every finite value survives the round trip bit
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// for bit. A payload copy would leak the incoming patterns 0x7C01 and
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// 0x7D00 instead.
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func TestWhereHalfCanonicalisesNaN(t *testing.T) {
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cond := mustFromInts(t, []int64{1, 0, 1, 0}, 4)
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// x: a signalling NaN with payload, 2, a negative signalling NaN, and
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// a slot the condition does not pick. y: 4, 3, 4 and -1.
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x := mustFromHalves(t, []uint16{0x7C01, 0x4000, 0xFE01, 0x3C00}, 4)
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y := mustFromHalves(t, []uint16{0x4400, 0x4200, 0x4400, 0xBC00}, 4)
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out, err := Where(cond, x, y)
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if err != nil {
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t.Fatalf("Where: %v", err)
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}
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if out.Dtype() != Float16 {
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t.Fatalf("Where answered dtype %s, want float16", out.Dtype())
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}
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want := []uint16{0x7E00, 0x4200, 0xFE00, 0xBC00}
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got := out.RawHalves()
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for i, w := range want {
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if got[i] != w {
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t.Fatalf("element %d = %#04x, want %#04x", i, got[i], w)
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}
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}
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}
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