78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
package numerics
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import (
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"math"
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"testing"
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)
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func TestRK4ExponentialDecay(t *testing.T) {
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// dAlt/dt = -Alt → exact: Alt(t) = Alt0 * exp(-t).
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f := func(_ float64, y GeoVec) GeoVec { return GeoVec{Altitude: -y.Altitude} }
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y := GeoVec{Altitude: 1}
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tnow, dt := 0.0, 0.01
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for range 100 {
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y = RK4Step(tnow, y, dt, f)
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tnow += dt
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}
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want := math.Exp(-1.0)
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if math.Abs(y.Altitude-want) > 1e-8 {
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t.Errorf("RK4 exp decay at t=1: got %v, want %v", y.Altitude, want)
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}
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}
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func TestRK4ReverseTime(t *testing.T) {
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// dAlt/dt = Alt → exact: Alt(t) = Alt0 * exp(t).
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f := func(_ float64, y GeoVec) GeoVec { return GeoVec{Altitude: y.Altitude} }
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y := GeoVec{Altitude: math.E}
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tnow, dt := 1.0, -0.01
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for range 100 {
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y = RK4Step(tnow, y, dt, f)
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tnow += dt
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}
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if math.Abs(y.Altitude-1.0) > 1e-8 {
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t.Errorf("RK4 reverse: got %v, want 1.0", y.Altitude)
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}
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}
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func TestRefineCrossing(t *testing.T) {
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y1 := GeoVec{Altitude: 1}
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y2 := GeoVec{Altitude: -1.5}
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crossed := func(_ float64, y GeoVec) bool { return y.Altitude <= 0 }
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tr, yr := RefineCrossing(0, y1, 1, y2, crossed, 0.001)
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if math.Abs(tr-0.4) > 0.01 {
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t.Errorf("refined t = %v, want ~0.4", tr)
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}
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if math.Abs(yr.Altitude) > 0.01 {
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t.Errorf("refined alt = %v, want ~0", yr.Altitude)
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}
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}
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func TestGeoAddWrapsLongitude(t *testing.T) {
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y := GeoAdd(GeoVec{Lng: 350}, 1, GeoVec{Lng: 20})
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if math.Abs(y.Lng-10) > 1e-9 {
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t.Errorf("GeoAdd wrap: lng = %v, want 10", y.Lng)
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}
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}
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func TestGeoLerpWrap(t *testing.T) {
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mid := GeoLerp(GeoVec{Lng: 350}, GeoVec{Lng: 10}, 0.5)
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if math.Abs(mid.Lng) > 1e-9 && math.Abs(mid.Lng-360) > 1e-9 {
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t.Errorf("GeoLerp lng wrap: %v, want 0 or 360", mid.Lng)
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}
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}
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func TestPathSoA(t *testing.T) {
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p := NewPath(4)
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p.Append(0, GeoVec{Lat: 1, Lng: 2, Altitude: 3})
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p.Append(60, GeoVec{Lat: 4, Lng: 5, Altitude: 6})
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if p.Len() != 2 {
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t.Fatalf("len = %d, want 2", p.Len())
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}
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tt, last := p.Last()
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if tt != 60 || last.Lat != 4 {
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t.Errorf("last = %v, %+v", tt, last)
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}
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}
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