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