| // Copyright ©2017 The Gonum Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package sampleuv |
| |
| import ( |
| "testing" |
| |
| "golang.org/x/exp/rand" |
| |
| "gonum.org/v1/gonum/floats" |
| ) |
| |
| func TestWithoutReplacement(t *testing.T) { |
| for cas, test := range []struct { |
| N int |
| K int |
| Src *rand.Rand |
| Trials int |
| Tol float64 |
| }{ |
| { |
| // Test with perm and source. |
| N: 10, K: 5, Src: rand.New(rand.NewSource(1)), |
| Trials: 100000, Tol: 1e-3, |
| }, |
| { |
| // Test without perm and with source. |
| N: 10, K: 3, Src: rand.New(rand.NewSource(1)), |
| Trials: 100000, Tol: 1e-3, |
| }, |
| } { |
| dist := make([]float64, test.N) |
| for trial := 0; trial < test.Trials; trial++ { |
| idxs := make([]int, test.K) |
| WithoutReplacement(idxs, test.N, test.Src) |
| |
| allDiff := true |
| for i := 0; i < len(idxs); i++ { |
| v := idxs[i] |
| for j := i + 1; j < len(idxs); j++ { |
| if v == idxs[j] { |
| allDiff = false |
| break |
| } |
| } |
| } |
| if !allDiff { |
| t.Errorf("Cas %d: Repeat in sampling. Idxs =%v", cas, idxs) |
| } |
| for _, v := range idxs { |
| dist[v]++ |
| } |
| } |
| div := 1 / (float64(test.Trials) * float64(test.K)) |
| floats.Scale(div, dist) |
| want := make([]float64, test.N) |
| for i := range want { |
| want[i] = 1 / float64(test.N) |
| } |
| if !floats.EqualApprox(want, dist, test.Tol) { |
| t.Errorf("Cas %d: biased sampling. Want = %v, got = %v", cas, want, dist) |
| } |
| } |
| } |