// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package testing
import (
"runtime"
)
// AllocsPerRun returns the average number of allocations during calls to f.
// Although the return value has type float64, it will always be an integral value.
//
// To compute the number of allocations, the function will first be run once as
// a warm-up. The average number of allocations over the specified number of
// runs will then be measured and returned.
//
// AllocsPerRun sets [runtime.GOMAXPROCS] to 1 during its measurement and will restore
// it before returning.
func AllocsPerRun(runs int, f func()) (avg float64) {
if parallelStart.Load() != parallelStop.Load() {
panic("testing: AllocsPerRun called during parallel test")
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
// Warm up the function
f()
// Measure the starting statistics
var memstats runtime.MemStats
runtime.ReadMemStats(&memstats)
mallocs := 0 - memstats.Mallocs
// Run the function the specified number of times
for i := 0; i < runs; i++ {
f()
}
// Read the final statistics
runtime.ReadMemStats(&memstats)
mallocs += memstats.Mallocs
// Average the mallocs over the runs (not counting the warm-up).
// We are forced to return a float64 because the API is silly, but do
// the division as integers so we can ask if AllocsPerRun()==1
// instead of AllocsPerRun()<2.
return float64(mallocs / uint64(runs))
}
