| // 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) |
| } |
| } |
