Source file src/strconv/ftoa_test.go

Documentation: strconv

     1  // Copyright 2009 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 strconv_test
     6  
     7  import (
     8  	"math"
     9  	"math/rand"
    10  	. "strconv"
    11  	"testing"
    12  )
    13  
    14  type ftoaTest struct {
    15  	f    float64
    16  	fmt  byte
    17  	prec int
    18  	s    string
    19  }
    20  
    21  func fdiv(a, b float64) float64 { return a / b }
    22  
    23  const (
    24  	below1e23 = 99999999999999974834176
    25  	above1e23 = 100000000000000008388608
    26  )
    27  
    28  var ftoatests = []ftoaTest{
    29  	{1, 'e', 5, "1.00000e+00"},
    30  	{1, 'f', 5, "1.00000"},
    31  	{1, 'g', 5, "1"},
    32  	{1, 'g', -1, "1"},
    33  	{1, 'x', -1, "0x1p+00"},
    34  	{1, 'x', 5, "0x1.00000p+00"},
    35  	{20, 'g', -1, "20"},
    36  	{20, 'x', -1, "0x1.4p+04"},
    37  	{1234567.8, 'g', -1, "1.2345678e+06"},
    38  	{1234567.8, 'x', -1, "0x1.2d687cccccccdp+20"},
    39  	{200000, 'g', -1, "200000"},
    40  	{200000, 'x', -1, "0x1.86ap+17"},
    41  	{200000, 'X', -1, "0X1.86AP+17"},
    42  	{2000000, 'g', -1, "2e+06"},
    43  
    44  	// g conversion and zero suppression
    45  	{400, 'g', 2, "4e+02"},
    46  	{40, 'g', 2, "40"},
    47  	{4, 'g', 2, "4"},
    48  	{.4, 'g', 2, "0.4"},
    49  	{.04, 'g', 2, "0.04"},
    50  	{.004, 'g', 2, "0.004"},
    51  	{.0004, 'g', 2, "0.0004"},
    52  	{.00004, 'g', 2, "4e-05"},
    53  	{.000004, 'g', 2, "4e-06"},
    54  
    55  	{0, 'e', 5, "0.00000e+00"},
    56  	{0, 'f', 5, "0.00000"},
    57  	{0, 'g', 5, "0"},
    58  	{0, 'g', -1, "0"},
    59  	{0, 'x', 5, "0x0.00000p+00"},
    60  
    61  	{-1, 'e', 5, "-1.00000e+00"},
    62  	{-1, 'f', 5, "-1.00000"},
    63  	{-1, 'g', 5, "-1"},
    64  	{-1, 'g', -1, "-1"},
    65  
    66  	{12, 'e', 5, "1.20000e+01"},
    67  	{12, 'f', 5, "12.00000"},
    68  	{12, 'g', 5, "12"},
    69  	{12, 'g', -1, "12"},
    70  
    71  	{123456700, 'e', 5, "1.23457e+08"},
    72  	{123456700, 'f', 5, "123456700.00000"},
    73  	{123456700, 'g', 5, "1.2346e+08"},
    74  	{123456700, 'g', -1, "1.234567e+08"},
    75  
    76  	{1.2345e6, 'e', 5, "1.23450e+06"},
    77  	{1.2345e6, 'f', 5, "1234500.00000"},
    78  	{1.2345e6, 'g', 5, "1.2345e+06"},
    79  
    80  	{1e23, 'e', 17, "9.99999999999999916e+22"},
    81  	{1e23, 'f', 17, "99999999999999991611392.00000000000000000"},
    82  	{1e23, 'g', 17, "9.9999999999999992e+22"},
    83  
    84  	{1e23, 'e', -1, "1e+23"},
    85  	{1e23, 'f', -1, "100000000000000000000000"},
    86  	{1e23, 'g', -1, "1e+23"},
    87  
    88  	{below1e23, 'e', 17, "9.99999999999999748e+22"},
    89  	{below1e23, 'f', 17, "99999999999999974834176.00000000000000000"},
    90  	{below1e23, 'g', 17, "9.9999999999999975e+22"},
    91  
    92  	{below1e23, 'e', -1, "9.999999999999997e+22"},
    93  	{below1e23, 'f', -1, "99999999999999970000000"},
    94  	{below1e23, 'g', -1, "9.999999999999997e+22"},
    95  
    96  	{above1e23, 'e', 17, "1.00000000000000008e+23"},
    97  	{above1e23, 'f', 17, "100000000000000008388608.00000000000000000"},
    98  	{above1e23, 'g', 17, "1.0000000000000001e+23"},
    99  
   100  	{above1e23, 'e', -1, "1.0000000000000001e+23"},
   101  	{above1e23, 'f', -1, "100000000000000010000000"},
   102  	{above1e23, 'g', -1, "1.0000000000000001e+23"},
   103  
   104  	{fdiv(5e-304, 1e20), 'g', -1, "5e-324"},   // avoid constant arithmetic
   105  	{fdiv(-5e-304, 1e20), 'g', -1, "-5e-324"}, // avoid constant arithmetic
   106  
   107  	{32, 'g', -1, "32"},
   108  	{32, 'g', 0, "3e+01"},
   109  
   110  	{100, 'x', -1, "0x1.9p+06"},
   111  	{100, 'y', -1, "%y"},
   112  
   113  	{math.NaN(), 'g', -1, "NaN"},
   114  	{-math.NaN(), 'g', -1, "NaN"},
   115  	{math.Inf(0), 'g', -1, "+Inf"},
   116  	{math.Inf(-1), 'g', -1, "-Inf"},
   117  	{-math.Inf(0), 'g', -1, "-Inf"},
   118  
   119  	{-1, 'b', -1, "-4503599627370496p-52"},
   120  
   121  	// fixed bugs
   122  	{0.9, 'f', 1, "0.9"},
   123  	{0.09, 'f', 1, "0.1"},
   124  	{0.0999, 'f', 1, "0.1"},
   125  	{0.05, 'f', 1, "0.1"},
   126  	{0.05, 'f', 0, "0"},
   127  	{0.5, 'f', 1, "0.5"},
   128  	{0.5, 'f', 0, "0"},
   129  	{1.5, 'f', 0, "2"},
   130  
   131  	// https://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
   132  	{2.2250738585072012e-308, 'g', -1, "2.2250738585072014e-308"},
   133  	// https://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
   134  	{2.2250738585072011e-308, 'g', -1, "2.225073858507201e-308"},
   135  
   136  	// Issue 2625.
   137  	{383260575764816448, 'f', 0, "383260575764816448"},
   138  	{383260575764816448, 'g', -1, "3.8326057576481645e+17"},
   139  
   140  	// Issue 29491.
   141  	{498484681984085570, 'f', -1, "498484681984085570"},
   142  	{-5.8339553793802237e+23, 'g', -1, "-5.8339553793802237e+23"},
   143  
   144  	// rounding
   145  	{2.275555555555555, 'x', -1, "0x1.23456789abcdep+01"},
   146  	{2.275555555555555, 'x', 0, "0x1p+01"},
   147  	{2.275555555555555, 'x', 2, "0x1.23p+01"},
   148  	{2.275555555555555, 'x', 16, "0x1.23456789abcde000p+01"},
   149  	{2.275555555555555, 'x', 21, "0x1.23456789abcde00000000p+01"},
   150  	{2.2755555510520935, 'x', -1, "0x1.2345678p+01"},
   151  	{2.2755555510520935, 'x', 6, "0x1.234568p+01"},
   152  	{2.275555431842804, 'x', -1, "0x1.2345668p+01"},
   153  	{2.275555431842804, 'x', 6, "0x1.234566p+01"},
   154  	{3.999969482421875, 'x', -1, "0x1.ffffp+01"},
   155  	{3.999969482421875, 'x', 4, "0x1.ffffp+01"},
   156  	{3.999969482421875, 'x', 3, "0x1.000p+02"},
   157  	{3.999969482421875, 'x', 2, "0x1.00p+02"},
   158  	{3.999969482421875, 'x', 1, "0x1.0p+02"},
   159  	{3.999969482421875, 'x', 0, "0x1p+02"},
   160  }
   161  
   162  func TestFtoa(t *testing.T) {
   163  	for i := 0; i < len(ftoatests); i++ {
   164  		test := &ftoatests[i]
   165  		s := FormatFloat(test.f, test.fmt, test.prec, 64)
   166  		if s != test.s {
   167  			t.Error("testN=64", test.f, string(test.fmt), test.prec, "want", test.s, "got", s)
   168  		}
   169  		x := AppendFloat([]byte("abc"), test.f, test.fmt, test.prec, 64)
   170  		if string(x) != "abc"+test.s {
   171  			t.Error("AppendFloat testN=64", test.f, string(test.fmt), test.prec, "want", "abc"+test.s, "got", string(x))
   172  		}
   173  		if float64(float32(test.f)) == test.f && test.fmt != 'b' {
   174  			s := FormatFloat(test.f, test.fmt, test.prec, 32)
   175  			if s != test.s {
   176  				t.Error("testN=32", test.f, string(test.fmt), test.prec, "want", test.s, "got", s)
   177  			}
   178  			x := AppendFloat([]byte("abc"), test.f, test.fmt, test.prec, 32)
   179  			if string(x) != "abc"+test.s {
   180  				t.Error("AppendFloat testN=32", test.f, string(test.fmt), test.prec, "want", "abc"+test.s, "got", string(x))
   181  			}
   182  		}
   183  	}
   184  }
   185  
   186  func TestFtoaRandom(t *testing.T) {
   187  	N := int(1e4)
   188  	if testing.Short() {
   189  		N = 100
   190  	}
   191  	t.Logf("testing %d random numbers with fast and slow FormatFloat", N)
   192  	for i := 0; i < N; i++ {
   193  		bits := uint64(rand.Uint32())<<32 | uint64(rand.Uint32())
   194  		x := math.Float64frombits(bits)
   195  
   196  		shortFast := FormatFloat(x, 'g', -1, 64)
   197  		SetOptimize(false)
   198  		shortSlow := FormatFloat(x, 'g', -1, 64)
   199  		SetOptimize(true)
   200  		if shortSlow != shortFast {
   201  			t.Errorf("%b printed as %s, want %s", x, shortFast, shortSlow)
   202  		}
   203  
   204  		prec := rand.Intn(12) + 5
   205  		shortFast = FormatFloat(x, 'e', prec, 64)
   206  		SetOptimize(false)
   207  		shortSlow = FormatFloat(x, 'e', prec, 64)
   208  		SetOptimize(true)
   209  		if shortSlow != shortFast {
   210  			t.Errorf("%b printed as %s, want %s", x, shortFast, shortSlow)
   211  		}
   212  	}
   213  }
   214  
   215  var ftoaBenches = []struct {
   216  	name    string
   217  	float   float64
   218  	fmt     byte
   219  	prec    int
   220  	bitSize int
   221  }{
   222  	{"Decimal", 33909, 'g', -1, 64},
   223  	{"Float", 339.7784, 'g', -1, 64},
   224  	{"Exp", -5.09e75, 'g', -1, 64},
   225  	{"NegExp", -5.11e-95, 'g', -1, 64},
   226  
   227  	{"Big", 123456789123456789123456789, 'g', -1, 64},
   228  	{"BinaryExp", -1, 'b', -1, 64},
   229  
   230  	{"32Integer", 33909, 'g', -1, 32},
   231  	{"32ExactFraction", 3.375, 'g', -1, 32},
   232  	{"32Point", 339.7784, 'g', -1, 32},
   233  	{"32Exp", -5.09e25, 'g', -1, 32},
   234  	{"32NegExp", -5.11e-25, 'g', -1, 32},
   235  
   236  	{"64Fixed1", 123456, 'e', 3, 64},
   237  	{"64Fixed2", 123.456, 'e', 3, 64},
   238  	{"64Fixed3", 1.23456e+78, 'e', 3, 64},
   239  	{"64Fixed4", 1.23456e-78, 'e', 3, 64},
   240  
   241  	// Trigger slow path (see issue #15672).
   242  	{"Slowpath64", 622666234635.3213e-320, 'e', -1, 64},
   243  }
   244  
   245  func BenchmarkFormatFloat(b *testing.B) {
   246  	for _, c := range ftoaBenches {
   247  		b.Run(c.name, func(b *testing.B) {
   248  			for i := 0; i < b.N; i++ {
   249  				FormatFloat(c.float, c.fmt, c.prec, c.bitSize)
   250  			}
   251  		})
   252  	}
   253  }
   254  
   255  func BenchmarkAppendFloat(b *testing.B) {
   256  	dst := make([]byte, 30)
   257  	for _, c := range ftoaBenches {
   258  		b.Run(c.name, func(b *testing.B) {
   259  			for i := 0; i < b.N; i++ {
   260  				AppendFloat(dst[:0], c.float, c.fmt, c.prec, c.bitSize)
   261  			}
   262  		})
   263  	}
   264  }
   265  

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