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recover_from_samples_test.go
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recover_from_samples_test.go
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package kzg
import (
"fmt"
"github.com/protolambda/go-kzg/bls"
"math/rand"
"testing"
)
func TestFFTSettings_RecoverPolyFromSamples_Simple(t *testing.T) {
// Create some random data, with padding...
fs := NewFFTSettings(2)
poly := make([]bls.Fr, fs.MaxWidth, fs.MaxWidth)
for i := uint64(0); i < fs.MaxWidth/2; i++ {
bls.AsFr(&poly[i], i)
}
for i := fs.MaxWidth / 2; i < fs.MaxWidth; i++ {
poly[i] = bls.ZERO
}
debugFrs("poly", poly)
// Get data for polynomial SLOW_INDICES
data, err := fs.FFT(poly, false)
if err != nil {
t.Fatal(err)
}
debugFrs("data", data)
subset := make([]*bls.Fr, fs.MaxWidth, fs.MaxWidth)
subset[0] = &data[0]
subset[3] = &data[3]
debugFrPtrs("subset", subset)
recovered, err := fs.RecoverPolyFromSamples(subset, fs.ZeroPolyViaMultiplication)
if err != nil {
t.Fatal(err)
}
debugFrs("recovered", recovered)
for i := range recovered {
if got := &recovered[i]; !bls.EqualFr(got, &data[i]) {
t.Errorf("recovery at index %d got %s but expected %s", i, bls.FrStr(got), bls.FrStr(&data[i]))
}
}
// And recover the original coeffs for good measure
back, err := fs.FFT(recovered, true)
if err != nil {
t.Fatal(err)
}
debugFrs("back", back)
for i := uint64(0); i < fs.MaxWidth/2; i++ {
if got := &back[i]; !bls.EqualFr(got, &poly[i]) {
t.Errorf("coeff at index %d got %s but expected %s", i, bls.FrStr(got), bls.FrStr(&poly[i]))
}
}
for i := fs.MaxWidth / 2; i < fs.MaxWidth; i++ {
if got := &back[i]; !bls.EqualZero(got) {
t.Errorf("expected zero padding in index %d", i)
}
}
}
func TestFFTSettings_RecoverPolyFromSamples(t *testing.T) {
// Create some random poly, with padding so we get redundant data
fs := NewFFTSettings(10)
poly := make([]bls.Fr, fs.MaxWidth, fs.MaxWidth)
for i := uint64(0); i < fs.MaxWidth/2; i++ {
bls.AsFr(&poly[i], i)
}
for i := fs.MaxWidth / 2; i < fs.MaxWidth; i++ {
poly[i] = bls.ZERO
}
debugFrs("poly", poly)
// Get coefficients for polynomial SLOW_INDICES
data, err := fs.FFT(poly, false)
if err != nil {
t.Fatal(err)
}
debugFrs("data", data)
// Util to pick a random subnet of the values
randomSubset := func(known uint64, rngSeed uint64) []*bls.Fr {
withMissingValues := make([]*bls.Fr, fs.MaxWidth, fs.MaxWidth)
for i := range data {
withMissingValues[i] = &data[i]
}
rng := rand.New(rand.NewSource(int64(rngSeed)))
missing := fs.MaxWidth - known
pruned := rng.Perm(int(fs.MaxWidth))[:missing]
for _, i := range pruned {
withMissingValues[i] = nil
}
return withMissingValues
}
// Try different amounts of known indices, and try it in multiple random ways
var lastKnown uint64 = 0
for knownRatio := 0.7; knownRatio < 1.0; knownRatio += 0.05 {
known := uint64(float64(fs.MaxWidth) * knownRatio)
if known == lastKnown {
continue
}
lastKnown = known
for i := 0; i < 3; i++ {
t.Run(fmt.Sprintf("random_subset_%d_known_%d", i, known), func(t *testing.T) {
subset := randomSubset(known, uint64(i))
debugFrPtrs("subset", subset)
recovered, err := fs.RecoverPolyFromSamples(subset, fs.ZeroPolyViaMultiplication)
if err != nil {
t.Fatal(err)
}
debugFrs("recovered", recovered)
for i := range recovered {
if got := &recovered[i]; !bls.EqualFr(got, &data[i]) {
t.Errorf("recovery at index %d got %s but expected %s", i, bls.FrStr(got), bls.FrStr(&data[i]))
}
}
// And recover the original coeffs for good measure
back, err := fs.FFT(recovered, true)
if err != nil {
t.Fatal(err)
}
debugFrs("back", back)
half := uint64(len(back)) / 2
for i := uint64(0); i < half; i++ {
if got := &back[i]; !bls.EqualFr(got, &poly[i]) {
t.Errorf("coeff at index %d got %s but expected %s", i, bls.FrStr(got), bls.FrStr(&poly[i]))
}
}
for i := half; i < fs.MaxWidth; i++ {
if got := &back[i]; !bls.EqualZero(got) {
t.Errorf("expected zero padding in index %d", i)
}
}
})
}
}
}