github.com/lfch/etcd-io/tests/v3@v3.0.0-20221004140520-eac99acd3e9d/functional/tester/cluster_shuffle.go (about)

     1  // Copyright 2018 The etcd Authors
     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 tester
    16  
    17  import (
    18  	"math/rand"
    19  	"time"
    20  
    21  	"go.uber.org/zap"
    22  )
    23  
    24  func (clus *Cluster) shuffleCases() {
    25  	rand.Seed(time.Now().UnixNano())
    26  	offset := rand.Intn(1000)
    27  	n := len(clus.cases)
    28  	cp := coprime(n)
    29  
    30  	css := make([]Case, n)
    31  	for i := 0; i < n; i++ {
    32  		css[i] = clus.cases[(cp*i+offset)%n]
    33  	}
    34  	clus.cases = css
    35  	clus.lg.Info("shuffled test failure cases", zap.Int("total", n))
    36  }
    37  
    38  /*
    39  x and y of GCD 1 are coprime to each other
    40  
    41  x1 = ( coprime of n * idx1 + offset ) % n
    42  x2 = ( coprime of n * idx2 + offset ) % n
    43  (x2 - x1) = coprime of n * (idx2 - idx1) % n
    44  
    45  	= (idx2 - idx1) = 1
    46  
    47  Consecutive x's are guaranteed to be distinct
    48  */
    49  func coprime(n int) int {
    50  	coprime := 1
    51  	for i := n / 2; i < n; i++ {
    52  		if gcd(i, n) == 1 {
    53  			coprime = i
    54  			break
    55  		}
    56  	}
    57  	return coprime
    58  }
    59  
    60  func gcd(x, y int) int {
    61  	if y == 0 {
    62  		return x
    63  	}
    64  	return gcd(y, x%y)
    65  }