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// run
// Copyright 2015 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.
// This test computes the precision of the compiler's internal multiprecision floats.
package main
import (
"fmt"
"math"
"runtime"
)
const ulp = (1.0 + (2.0 / 3.0)) - (5.0 / 3.0)
func main() {
// adjust precision depending on compiler
var prec float64
switch runtime.Compiler {
case "gc":
prec = math.Inf(1) // exact precision using rational arithmetic
case "gccgo":
prec = 256
default:
// unknown compiler
return
}
p := 1 - math.Log(math.Abs(ulp))/math.Log(2)
if math.Abs(p-prec) > 1e-10 {
fmt.Printf("BUG: got %g; want %g\n", p, prec)
}
}
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