...
Run Format

Source file src/math/big/ratconv_test.go

Documentation: math/big

  // 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.
  
  package big
  
  import (
  	"bytes"
  	"fmt"
  	"math"
  	"strconv"
  	"strings"
  	"testing"
  )
  
  type StringTest struct {
  	in, out string
  	ok      bool
  }
  
  var setStringTests = []StringTest{
  	{"0", "0", true},
  	{"-0", "0", true},
  	{"1", "1", true},
  	{"-1", "-1", true},
  	{"1.", "1", true},
  	{"1e0", "1", true},
  	{"1.e1", "10", true},
  	{in: "1e"},
  	{in: "1.e"},
  	{in: "1e+14e-5"},
  	{in: "1e4.5"},
  	{in: "r"},
  	{in: "a/b"},
  	{in: "a.b"},
  	{"-0.1", "-1/10", true},
  	{"-.1", "-1/10", true},
  	{"2/4", "1/2", true},
  	{".25", "1/4", true},
  	{"-1/5", "-1/5", true},
  	{"8129567.7690E14", "812956776900000000000", true},
  	{"78189e+4", "781890000", true},
  	{"553019.8935e+8", "55301989350000", true},
  	{"98765432109876543210987654321e-10", "98765432109876543210987654321/10000000000", true},
  	{"9877861857500000E-7", "3951144743/4", true},
  	{"2169378.417e-3", "2169378417/1000000", true},
  	{"884243222337379604041632732738665534", "884243222337379604041632732738665534", true},
  	{"53/70893980658822810696", "53/70893980658822810696", true},
  	{"106/141787961317645621392", "53/70893980658822810696", true},
  	{"204211327800791583.81095", "4084226556015831676219/20000", true},
  	{"0e9999999999", "0", true}, // issue #16176
  	{in: "1/0"},
  	{in: "4/3/2"}, // issue 17001
  	{in: "4/3/"},
  	{in: "4/3."},
  	{in: "4/"},
  }
  
  // These are not supported by fmt.Fscanf.
  var setStringTests2 = []StringTest{
  	{"0x10", "16", true},
  	{"-010/1", "-8", true}, // TODO(gri) should we even permit octal here?
  	{"-010.", "-10", true},
  	{"0x10/0x20", "1/2", true},
  	{"0b1000/3", "8/3", true},
  	{in: "4/3x"},
  	// TODO(gri) add more tests
  }
  
  func TestRatSetString(t *testing.T) {
  	var tests []StringTest
  	tests = append(tests, setStringTests...)
  	tests = append(tests, setStringTests2...)
  
  	for i, test := range tests {
  		x, ok := new(Rat).SetString(test.in)
  
  		if ok {
  			if !test.ok {
  				t.Errorf("#%d SetString(%q) expected failure", i, test.in)
  			} else if x.RatString() != test.out {
  				t.Errorf("#%d SetString(%q) got %s want %s", i, test.in, x.RatString(), test.out)
  			}
  		} else if x != nil {
  			t.Errorf("#%d SetString(%q) got %p want nil", i, test.in, x)
  		}
  	}
  }
  
  func TestRatScan(t *testing.T) {
  	var buf bytes.Buffer
  	for i, test := range setStringTests {
  		x := new(Rat)
  		buf.Reset()
  		buf.WriteString(test.in)
  
  		_, err := fmt.Fscanf(&buf, "%v", x)
  		if err == nil != test.ok {
  			if test.ok {
  				t.Errorf("#%d (%s) error: %s", i, test.in, err)
  			} else {
  				t.Errorf("#%d (%s) expected error", i, test.in)
  			}
  			continue
  		}
  		if err == nil && x.RatString() != test.out {
  			t.Errorf("#%d got %s want %s", i, x.RatString(), test.out)
  		}
  	}
  }
  
  var floatStringTests = []struct {
  	in   string
  	prec int
  	out  string
  }{
  	{"0", 0, "0"},
  	{"0", 4, "0.0000"},
  	{"1", 0, "1"},
  	{"1", 2, "1.00"},
  	{"-1", 0, "-1"},
  	{"0.05", 1, "0.1"},
  	{"-0.05", 1, "-0.1"},
  	{".25", 2, "0.25"},
  	{".25", 1, "0.3"},
  	{".25", 3, "0.250"},
  	{"-1/3", 3, "-0.333"},
  	{"-2/3", 4, "-0.6667"},
  	{"0.96", 1, "1.0"},
  	{"0.999", 2, "1.00"},
  	{"0.9", 0, "1"},
  	{".25", -1, "0"},
  	{".55", -1, "1"},
  }
  
  func TestFloatString(t *testing.T) {
  	for i, test := range floatStringTests {
  		x, _ := new(Rat).SetString(test.in)
  
  		if x.FloatString(test.prec) != test.out {
  			t.Errorf("#%d got %s want %s", i, x.FloatString(test.prec), test.out)
  		}
  	}
  }
  
  // Test inputs to Rat.SetString. The prefix "long:" causes the test
  // to be skipped except in -long mode.  (The threshold is about 500us.)
  var float64inputs = []string{
  	// Constants plundered from strconv/testfp.txt.
  
  	// Table 1: Stress Inputs for Conversion to 53-bit Binary, < 1/2 ULP
  	"5e+125",
  	"69e+267",
  	"999e-026",
  	"7861e-034",
  	"75569e-254",
  	"928609e-261",
  	"9210917e+080",
  	"84863171e+114",
  	"653777767e+273",
  	"5232604057e-298",
  	"27235667517e-109",
  	"653532977297e-123",
  	"3142213164987e-294",
  	"46202199371337e-072",
  	"231010996856685e-073",
  	"9324754620109615e+212",
  	"78459735791271921e+049",
  	"272104041512242479e+200",
  	"6802601037806061975e+198",
  	"20505426358836677347e-221",
  	"836168422905420598437e-234",
  	"4891559871276714924261e+222",
  
  	// Table 2: Stress Inputs for Conversion to 53-bit Binary, > 1/2 ULP
  	"9e-265",
  	"85e-037",
  	"623e+100",
  	"3571e+263",
  	"81661e+153",
  	"920657e-023",
  	"4603285e-024",
  	"87575437e-309",
  	"245540327e+122",
  	"6138508175e+120",
  	"83356057653e+193",
  	"619534293513e+124",
  	"2335141086879e+218",
  	"36167929443327e-159",
  	"609610927149051e-255",
  	"3743626360493413e-165",
  	"94080055902682397e-242",
  	"899810892172646163e+283",
  	"7120190517612959703e+120",
  	"25188282901709339043e-252",
  	"308984926168550152811e-052",
  	"6372891218502368041059e+064",
  
  	// Table 14: Stress Inputs for Conversion to 24-bit Binary, <1/2 ULP
  	"5e-20",
  	"67e+14",
  	"985e+15",
  	"7693e-42",
  	"55895e-16",
  	"996622e-44",
  	"7038531e-32",
  	"60419369e-46",
  	"702990899e-20",
  	"6930161142e-48",
  	"25933168707e+13",
  	"596428896559e+20",
  
  	// Table 15: Stress Inputs for Conversion to 24-bit Binary, >1/2 ULP
  	"3e-23",
  	"57e+18",
  	"789e-35",
  	"2539e-18",
  	"76173e+28",
  	"887745e-11",
  	"5382571e-37",
  	"82381273e-35",
  	"750486563e-38",
  	"3752432815e-39",
  	"75224575729e-45",
  	"459926601011e+15",
  
  	// Constants plundered from strconv/atof_test.go.
  
  	"0",
  	"1",
  	"+1",
  	"1e23",
  	"1E23",
  	"100000000000000000000000",
  	"1e-100",
  	"123456700",
  	"99999999999999974834176",
  	"100000000000000000000001",
  	"100000000000000008388608",
  	"100000000000000016777215",
  	"100000000000000016777216",
  	"-1",
  	"-0.1",
  	"-0", // NB: exception made for this input
  	"1e-20",
  	"625e-3",
  
  	// largest float64
  	"1.7976931348623157e308",
  	"-1.7976931348623157e308",
  	// next float64 - too large
  	"1.7976931348623159e308",
  	"-1.7976931348623159e308",
  	// the border is ...158079
  	// borderline - okay
  	"1.7976931348623158e308",
  	"-1.7976931348623158e308",
  	// borderline - too large
  	"1.797693134862315808e308",
  	"-1.797693134862315808e308",
  
  	// a little too large
  	"1e308",
  	"2e308",
  	"1e309",
  
  	// way too large
  	"1e310",
  	"-1e310",
  	"1e400",
  	"-1e400",
  	"long:1e400000",
  	"long:-1e400000",
  
  	// denormalized
  	"1e-305",
  	"1e-306",
  	"1e-307",
  	"1e-308",
  	"1e-309",
  	"1e-310",
  	"1e-322",
  	// smallest denormal
  	"5e-324",
  	"4e-324",
  	"3e-324",
  	// too small
  	"2e-324",
  	// way too small
  	"1e-350",
  	"long:1e-400000",
  	// way too small, negative
  	"-1e-350",
  	"long:-1e-400000",
  
  	// try to overflow exponent
  	// [Disabled: too slow and memory-hungry with rationals.]
  	// "1e-4294967296",
  	// "1e+4294967296",
  	// "1e-18446744073709551616",
  	// "1e+18446744073709551616",
  
  	// http://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
  	"2.2250738585072012e-308",
  	// http://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
  	"2.2250738585072011e-308",
  
  	// A very large number (initially wrongly parsed by the fast algorithm).
  	"4.630813248087435e+307",
  
  	// A different kind of very large number.
  	"22.222222222222222",
  	"long:2." + strings.Repeat("2", 4000) + "e+1",
  
  	// Exactly halfway between 1 and math.Nextafter(1, 2).
  	// Round to even (down).
  	"1.00000000000000011102230246251565404236316680908203125",
  	// Slightly lower; still round down.
  	"1.00000000000000011102230246251565404236316680908203124",
  	// Slightly higher; round up.
  	"1.00000000000000011102230246251565404236316680908203126",
  	// Slightly higher, but you have to read all the way to the end.
  	"long:1.00000000000000011102230246251565404236316680908203125" + strings.Repeat("0", 10000) + "1",
  
  	// Smallest denormal, 2^(-1022-52)
  	"4.940656458412465441765687928682213723651e-324",
  	// Half of smallest denormal, 2^(-1022-53)
  	"2.470328229206232720882843964341106861825e-324",
  	// A little more than the exact half of smallest denormal
  	// 2^-1075 + 2^-1100.  (Rounds to 1p-1074.)
  	"2.470328302827751011111470718709768633275e-324",
  	// The exact halfway between smallest normal and largest denormal:
  	// 2^-1022 - 2^-1075.  (Rounds to 2^-1022.)
  	"2.225073858507201136057409796709131975935e-308",
  
  	"1152921504606846975",  //   1<<60 - 1
  	"-1152921504606846975", // -(1<<60 - 1)
  	"1152921504606846977",  //   1<<60 + 1
  	"-1152921504606846977", // -(1<<60 + 1)
  
  	"1/3",
  }
  
  // isFinite reports whether f represents a finite rational value.
  // It is equivalent to !math.IsNan(f) && !math.IsInf(f, 0).
  func isFinite(f float64) bool {
  	return math.Abs(f) <= math.MaxFloat64
  }
  
  func TestFloat32SpecialCases(t *testing.T) {
  	for _, input := range float64inputs {
  		if strings.HasPrefix(input, "long:") {
  			if !*long {
  				continue
  			}
  			input = input[len("long:"):]
  		}
  
  		r, ok := new(Rat).SetString(input)
  		if !ok {
  			t.Errorf("Rat.SetString(%q) failed", input)
  			continue
  		}
  		f, exact := r.Float32()
  
  		// 1. Check string -> Rat -> float32 conversions are
  		// consistent with strconv.ParseFloat.
  		// Skip this check if the input uses "a/b" rational syntax.
  		if !strings.Contains(input, "/") {
  			e64, _ := strconv.ParseFloat(input, 32)
  			e := float32(e64)
  
  			// Careful: negative Rats too small for
  			// float64 become -0, but Rat obviously cannot
  			// preserve the sign from SetString("-0").
  			switch {
  			case math.Float32bits(e) == math.Float32bits(f):
  				// Ok: bitwise equal.
  			case f == 0 && r.Num().BitLen() == 0:
  				// Ok: Rat(0) is equivalent to both +/- float64(0).
  			default:
  				t.Errorf("strconv.ParseFloat(%q) = %g (%b), want %g (%b); delta = %g", input, e, e, f, f, f-e)
  			}
  		}
  
  		if !isFinite(float64(f)) {
  			continue
  		}
  
  		// 2. Check f is best approximation to r.
  		if !checkIsBestApprox32(t, f, r) {
  			// Append context information.
  			t.Errorf("(input was %q)", input)
  		}
  
  		// 3. Check f->R->f roundtrip is non-lossy.
  		checkNonLossyRoundtrip32(t, f)
  
  		// 4. Check exactness using slow algorithm.
  		if wasExact := new(Rat).SetFloat64(float64(f)).Cmp(r) == 0; wasExact != exact {
  			t.Errorf("Rat.SetString(%q).Float32().exact = %t, want %t", input, exact, wasExact)
  		}
  	}
  }
  
  func TestFloat64SpecialCases(t *testing.T) {
  	for _, input := range float64inputs {
  		if strings.HasPrefix(input, "long:") {
  			if !*long {
  				continue
  			}
  			input = input[len("long:"):]
  		}
  
  		r, ok := new(Rat).SetString(input)
  		if !ok {
  			t.Errorf("Rat.SetString(%q) failed", input)
  			continue
  		}
  		f, exact := r.Float64()
  
  		// 1. Check string -> Rat -> float64 conversions are
  		// consistent with strconv.ParseFloat.
  		// Skip this check if the input uses "a/b" rational syntax.
  		if !strings.Contains(input, "/") {
  			e, _ := strconv.ParseFloat(input, 64)
  
  			// Careful: negative Rats too small for
  			// float64 become -0, but Rat obviously cannot
  			// preserve the sign from SetString("-0").
  			switch {
  			case math.Float64bits(e) == math.Float64bits(f):
  				// Ok: bitwise equal.
  			case f == 0 && r.Num().BitLen() == 0:
  				// Ok: Rat(0) is equivalent to both +/- float64(0).
  			default:
  				t.Errorf("strconv.ParseFloat(%q) = %g (%b), want %g (%b); delta = %g", input, e, e, f, f, f-e)
  			}
  		}
  
  		if !isFinite(f) {
  			continue
  		}
  
  		// 2. Check f is best approximation to r.
  		if !checkIsBestApprox64(t, f, r) {
  			// Append context information.
  			t.Errorf("(input was %q)", input)
  		}
  
  		// 3. Check f->R->f roundtrip is non-lossy.
  		checkNonLossyRoundtrip64(t, f)
  
  		// 4. Check exactness using slow algorithm.
  		if wasExact := new(Rat).SetFloat64(f).Cmp(r) == 0; wasExact != exact {
  			t.Errorf("Rat.SetString(%q).Float64().exact = %t, want %t", input, exact, wasExact)
  		}
  	}
  }
  

View as plain text