github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/workload/workloadimpl/precomputedrand_test.go (about)

     1  // Copyright 2019 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package workloadimpl_test
    12  
    13  import (
    14  	"fmt"
    15  	"testing"
    16  
    17  	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
    18  	"github.com/cockroachdb/cockroach/pkg/workload/workloadimpl"
    19  	"github.com/stretchr/testify/require"
    20  	"golang.org/x/exp/rand"
    21  )
    22  
    23  const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    24  
    25  func TestPrecomputedRand(t *testing.T) {
    26  	const precomputeLen = 100
    27  
    28  	seed0 := workloadimpl.PrecomputedRandInit(rand.NewSource(0), precomputeLen, alphabet)()
    29  	seed1 := workloadimpl.PrecomputedRandInit(rand.NewSource(1), precomputeLen, alphabet)()
    30  	numbers := workloadimpl.PrecomputedRandInit(rand.NewSource(0), precomputeLen, `0123456789`)()
    31  
    32  	const shorterThanPrecomputed, longerThanPrecomputed = precomputeLen / 10, precomputeLen + 7
    33  
    34  	offset := 0
    35  	fillBytes := func(pr workloadimpl.PrecomputedRand, length int) []byte {
    36  		buf := make([]byte, length)
    37  		offset = pr.FillBytes(offset, buf)
    38  		return buf
    39  	}
    40  
    41  	short0 := fillBytes(seed0, shorterThanPrecomputed)
    42  	long0 := fillBytes(seed0, longerThanPrecomputed)
    43  
    44  	// Offset has advanced, we should get a different result.
    45  	short0Different := fillBytes(seed0, shorterThanPrecomputed)
    46  	require.NotEqual(t, short0, short0Different)
    47  
    48  	// Reset the offset and verify that the results are repeatable
    49  	offset = 0
    50  	short0B := fillBytes(seed0, shorterThanPrecomputed)
    51  	long0B := fillBytes(seed0, longerThanPrecomputed)
    52  	require.Equal(t, short0, short0B)
    53  	require.Equal(t, long0, long0B)
    54  
    55  	// Reset the offset and verify that a different seed gets different results.
    56  	offset = 0
    57  	short1 := fillBytes(seed1, shorterThanPrecomputed)
    58  	long1 := fillBytes(seed1, longerThanPrecomputed)
    59  	require.NotEqual(t, short0, short1)
    60  	require.NotEqual(t, long0, long1)
    61  
    62  	// Reset the offset and verify that a different alphabet gets different
    63  	// results.
    64  	offset = 0
    65  	shortNumbers := fillBytes(numbers, shorterThanPrecomputed)
    66  	longNumbers := fillBytes(numbers, longerThanPrecomputed)
    67  	require.NotEqual(t, short0, shortNumbers)
    68  	require.NotEqual(t, long0, longNumbers)
    69  }
    70  
    71  func BenchmarkPrecomputedRand(b *testing.B) {
    72  	const precomputeLen = 10000
    73  	pr := workloadimpl.PrecomputedRandInit(
    74  		rand.NewSource(uint64(timeutil.Now().UnixNano())), precomputeLen, alphabet)()
    75  
    76  	const shortLen, mediumLen, longLen = 2, 100, 100000
    77  	scratch := make([]byte, longLen)
    78  	var randOffset int
    79  
    80  	for _, l := range []int{shortLen, mediumLen, longLen} {
    81  		b.Run(fmt.Sprintf(`len=%d`, l), func(b *testing.B) {
    82  			randOffset = 0
    83  			buf := scratch[:l]
    84  			for i := 0; i < b.N; i++ {
    85  				randOffset = pr.FillBytes(randOffset, buf)
    86  			}
    87  			b.SetBytes(int64(len(buf)))
    88  		})
    89  	}
    90  }