57 lines
1.7 KiB
Go
57 lines
1.7 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 stats
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import (
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"testing"
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"sourcedock.dev/petrbalvin/tensor/internal/core"
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)
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// The pooled pair-slope buffer is sliced to the pair count before the
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// median reads it: a reused buffer carries a longer tail from an earlier
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// fit, and the median must never see it. The sequence below makes the
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// long fit prime the pool and the short fits reuse it; a garbage
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// collection between the calls would drop the entry and weaken the pin,
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// so the fits run back to back.
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func TestTheilSenPooledReuseKeepsExactSlope(t *testing.T) {
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// Both fixtures sit exactly on y = 3x - 2, so every pair slope is
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// exactly 3 and the answers are exact whatever the pair order.
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makeLine := func(n int) (*core.Array, *core.Array) {
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xs := make([]float64, n)
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ys := make([]float64, n)
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for i := range n {
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xs[i] = float64(i) + 0.5
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ys[i] = 3*xs[i] - 2
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}
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x, err := core.FromFloats(xs, n)
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if err != nil {
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t.Fatalf("FromFloats: %v", err)
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}
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y, err := core.FromFloats(ys, n)
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if err != nil {
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t.Fatalf("FromFloats: %v", err)
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}
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return x, y
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}
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bigX, bigY := makeLine(300)
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smallX, smallY := makeLine(40)
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if _, _, err := TheilSenRegression(bigX, bigY); err != nil {
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t.Fatalf("long fit: %v", err)
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}
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for round := range 3 {
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intercept, slope, err := TheilSenRegression(smallX, smallY)
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if err != nil {
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t.Fatalf("short fit %d: %v", round, err)
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}
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if slope != 3 {
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t.Fatalf("short fit %d: slope = %v, want exactly 3", round, slope)
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}
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if intercept != -2 {
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t.Fatalf("short fit %d: intercept = %v, want exactly -2", round, intercept)
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}
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}
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}
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