github.com/jingcheng-WU/gonum@v0.9.1-0.20210323123734-f1a2a11a8f7b/stat/distmat/permutation_test.go (about)

     1  // Copyright ©2020 The Gonum Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package distmat
     6  
     7  import (
     8  	"testing"
     9  
    10  	"golang.org/x/exp/rand"
    11  
    12  	"github.com/jingcheng-WU/gonum/mat"
    13  )
    14  
    15  func TestUniformPermutation(t *testing.T) {
    16  	up := NewUniformPermutation(rand.NewSource(1))
    17  	for _, n := range []int{10, 32, 64, 100} {
    18  		m := mat.NewDense(n, n, nil)
    19  		up.PermTo(m)
    20  		// Test that each row and column satisfies the permutation matrix
    21  		// invariant that all rows and columns have a single unit element
    22  		// and the remaining elements are zero.
    23  		for i := 0; i < n; i++ {
    24  			checkHasSingleUnitElement(t, "row", i, mat.Row(nil, i, m))
    25  			checkHasSingleUnitElement(t, "col", i, mat.Col(nil, i, m))
    26  		}
    27  	}
    28  }
    29  
    30  func checkHasSingleUnitElement(t *testing.T, dir string, n int, v []float64) {
    31  	t.Helper()
    32  	var sum float64
    33  	for i, x := range v {
    34  		switch x {
    35  		case 0, 1:
    36  			sum += x
    37  		default:
    38  			t.Errorf("unexpected value in %s %d position %d: %v", dir, n, i, v)
    39  		}
    40  	}
    41  	if sum != 1 {
    42  		t.Errorf("%s %d is not a valid vector: %v", dir, n, v)
    43  	}
    44  }