tensor/signal/transform_cache_pins_test.go

package signal

import (
	"math"
	"testing"

	"sourcedock.dev/petrbalvin/tensor/internal/core"
)

// The fit cache is keyed by the window and the order together; a key
// that lost the order would answer one order's weights for another.
// Each reference is computed with an empty cache, so a collision
// between the two keys cannot hide behind a shared fit row.
func TestSavitzkyGolayCacheKeyCarriesOrder(t *testing.T) {
	n := 64
	vals := make([]float64, n)
	for i := range vals {
		x := float64(i) / float64(n-1)
		vals[i] = x*x*x - 2*x
	}
	src, err := core.FromFloats(vals, n)
	if err != nil {
		t.Fatal(err)
	}
	run := func() (map[int][]float64, error) {
		sgFitKeys = map[sgFitKey]*sgFits{}
		got := map[int][]float64{}
		for _, order := range []int{1, 2, 3} {
			out, err := SavitzkyGolay(src, 7, order)
			if err != nil {
				return nil, err
			}
			raw := out.RawFloats()
			got[order] = append([]float64(nil), raw...)
		}
		return got, nil
	}
	want, err := run()
	if err != nil {
		t.Fatal(err)
	}
	got, err := run()
	if err != nil {
		t.Fatal(err)
	}
	// The orders must differ from one another on a curved signal,
	// otherwise the comparison below pins nothing.
	for a := 1; a <= 2; a++ {
		for i := range want[a] {
			if want[a][i] != want[a+1][i] {
				break
			}
			if i == len(want[a])-1 {
				t.Fatalf("orders %d and %d agree everywhere; the fixture does not separate them", a, a+1)
			}
		}
	}
	for order := 1; order <= 3; order++ {
		for i := range want[order] {
			if want[order][i] != got[order][i] {
				t.Fatalf("order %d, sample %d: cached run answered %v, fresh-cache run answered %v", order, i, got[order][i], want[order][i])
			}
		}
	}
}

// Sweeping more scales than the cache's entry cap must leave every
// answer unchanged and the cache bounded.
func TestCWTSpectrumCacheCap(t *testing.T) {
	n := 32
	vals := make([]float64, n)
	for i := range vals {
		vals[i] = math.Sin(2*math.Pi*float64(i)/8) + 0.25*math.Sin(2*math.Pi*float64(i)/3)
	}
	src, err := core.FromFloats(vals, n)
	if err != nil {
		t.Fatal(err)
	}
	const scales = cwtSpectrumCacheMax + 8
	scaleList := make([]float64, scales)
	for k := range scaleList {
		scaleList[k] = 2 + float64(k)*0.5
	}
	build := func() [][]complex128 {
		cwtSpectrumKeys = map[cwtSpectrumKey][]complex128{}
		out, err := CWT(src, Morlet, scaleList, 1)
		if err != nil {
			t.Fatalf("CWT: %v", err)
		}
		raw, err := out.ComplexValues("CWT")
		if err != nil {
			t.Fatalf("ComplexValues: %v", err)
		}
		rows := make([][]complex128, len(scaleList))
		for k := range rows {
			rows[k] = append([]complex128(nil), raw[k*n:(k+1)*n]...)
		}
		return rows
	}
	want := build()
	got := build()
	if len(cwtSpectrumKeys) > cwtSpectrumCacheMax {
		t.Fatalf("the spectrum cache holds %d entries over the cap %d", len(cwtSpectrumKeys), cwtSpectrumCacheMax)
	}
	for k := range want {
		for i := range want[k] {
			if want[k][i] != got[k][i] {
				t.Fatalf("scale %v, sample %d: %v vs %v", scaleList[k], i, got[k][i], want[k][i])
			}
		}
	}
}