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 // Copyright 2018 The etcd Authors // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package tester import ( "math/rand" "time" "go.uber.org/zap" ) func (clus *Cluster) shuffleCases() { rand.Seed(time.Now().UnixNano()) offset := rand.Intn(1000) n := len(clus.cases) cp := coprime(n) css := make([]Case, n) for i := 0; i < n; i++ { css[i] = clus.cases[(cp*i+offset)%n] } clus.cases = css clus.lg.Info("shuffled test failure cases", zap.Int("total", n)) } /* x and y of GCD 1 are coprime to each other x1 = ( coprime of n * idx1 + offset ) % n x2 = ( coprime of n * idx2 + offset ) % n (x2 - x1) = coprime of n * (idx2 - idx1) % n = (idx2 - idx1) = 1 Consecutive x's are guaranteed to be distinct */ func coprime(n int) int { coprime := 1 for i := n / 2; i < n; i++ { if gcd(i, n) == 1 { coprime = i break } } return coprime } func gcd(x, y int) int { if y == 0 { return x } return gcd(y, x%y) }