1 // Copyright 2013 The Go 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 testing 6 7 import ( 8 "runtime" 9 ) 10 11 // AllocsPerRun returns the average number of allocations during calls to f. 12 // Although the return value has type float64, it will always be an integral value. 13 // 14 // To compute the number of allocations, the function will first be run once as 15 // a warm-up. The average number of allocations over the specified number of 16 // runs will then be measured and returned. 17 // 18 // AllocsPerRun sets GOMAXPROCS to 1 during its measurement and will restore 19 // it before returning. 20 func AllocsPerRun(runs int, f func()) (avg float64) { 21 defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1)) 22 23 // Warm up the function 24 f() 25 26 // Measure the starting statistics 27 var memstats runtime.MemStats 28 runtime.ReadMemStats(&memstats) 29 mallocs := 0 - memstats.Mallocs 30 31 // Run the function the specified number of times 32 for i := 0; i < runs; i++ { 33 f() 34 } 35 36 // Read the final statistics 37 runtime.ReadMemStats(&memstats) 38 mallocs += memstats.Mallocs 39 40 // Average the mallocs over the runs (not counting the warm-up). 41 // We are forced to return a float64 because the API is silly, but do 42 // the division as integers so we can ask if AllocsPerRun()==1 43 // instead of AllocsPerRun()<2. 44 return float64(mallocs / uint64(runs)) 45 } 46