github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/internal/mathutil/rand_test.go (about)

     1  // Copyright 2020 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package mathutil
    16  
    17  import (
    18  	"testing"
    19  	"time"
    20  
    21  	"github.com/stretchr/testify/require"
    22  )
    23  
    24  func TestRandWithTime(t *testing.T) {
    25  	rng1 := NewWithTime()
    26  	// NOTE: On windows platform, this Sleep is necessary. Because time.Now() is
    27  	// imprecise, calling UnixNano() twice returns the same value. We have to make
    28  	// sure the elapsed time is longer than 1ms to get different values.
    29  	time.Sleep(time.Millisecond)
    30  	rng2 := NewWithTime()
    31  	got1 := rng1.Gen()
    32  	got2 := rng2.Gen()
    33  	require.True(t, got1 < 1.0)
    34  	require.True(t, got1 >= 0.0)
    35  	require.True(t, got1 != rng1.Gen())
    36  	require.True(t, got2 < 1.0)
    37  	require.True(t, got2 >= 0.0)
    38  	require.True(t, got2 != rng2.Gen())
    39  	require.True(t, got1 != got2)
    40  }
    41  
    42  func TestRandWithSeed(t *testing.T) {
    43  	tests := [4]struct {
    44  		seed  int64
    45  		once  float64
    46  		twice float64
    47  	}{{0, 0.15522042769493574, 0.620881741513388},
    48  		{1, 0.40540353712197724, 0.8716141803857071},
    49  		{-1, 0.9050373219931845, 0.37014932126752037},
    50  		{9223372036854775807, 0.9050373219931845, 0.37014932126752037}}
    51  	for _, test := range tests {
    52  		rng := NewWithSeed(test.seed)
    53  		got1 := rng.Gen()
    54  		require.Equal(t, got1, test.once)
    55  		got2 := rng.Gen()
    56  		require.Equal(t, got2, test.twice)
    57  	}
    58  }
    59  
    60  func TestRandWithSeed1AndSeed2(t *testing.T) {
    61  	seed1 := uint32(10000000)
    62  	seed2 := uint32(1000000)
    63  
    64  	rng := NewWithTime()
    65  	rng.SetSeed1(seed1)
    66  	rng.SetSeed2(seed2)
    67  
    68  	require.Equal(t, rng.Gen(), 0.028870999839968048)
    69  	require.Equal(t, rng.Gen(), 0.11641535266900002)
    70  	require.Equal(t, rng.Gen(), 0.49546379455874096)
    71  	require.Equal(t, rng.GetSeed1(), uint32(532000198))
    72  	require.Equal(t, rng.GetSeed2(), uint32(689000330))
    73  }