library/core/tests/num/dec2flt/rawfp.rs

   1 use core::num::dec2flt::rawfp::RawFloat;
   2 use core::num::dec2flt::rawfp::{fp_to_float, next_float, prev_float, round_normal};
   3 use core::num::diy_float::Fp;
   4
   5 fn integer_decode(f: f64) -> (u64, i16, i8) {
   6     RawFloat::integer_decode(f)
   7 }
   8
   9 #[test]
  10 fn fp_to_float_half_to_even() {
  11     fn is_normalized(sig: u64) -> bool {
  12         // intentionally written without {min,max}_sig() as a sanity check
  13         sig >> 52 == 1 && sig >> 53 == 0
  14     }
  15
  16     fn conv(sig: u64) -> u64 {
  17         // The significands are perfectly in range, so the exponent should not matter
  18         let (m1, e1, _) = integer_decode(fp_to_float::<f64>(Fp { f: sig, e: 0 }));
  19         assert_eq!(e1, 0 + 64 - 53);
  20         let (m2, e2, _) = integer_decode(fp_to_float::<f64>(Fp { f: sig, e: 55 }));
  21         assert_eq!(e2, 55 + 64 - 53);
  22         assert_eq!(m2, m1);
  23         let (m3, e3, _) = integer_decode(fp_to_float::<f64>(Fp { f: sig, e: -78 }));
  24         assert_eq!(e3, -78 + 64 - 53);
  25         assert_eq!(m3, m2);
  26         m3
  27     }
  28
  29     let odd = 0x1F_EDCB_A012_345F;
  30     let even = odd - 1;
  31     assert!(is_normalized(odd));
  32     assert!(is_normalized(even));
  33     assert_eq!(conv(odd << 11), odd);
  34     assert_eq!(conv(even << 11), even);
  35     assert_eq!(conv(odd << 11 | 1 << 10), odd + 1);
  36     assert_eq!(conv(even << 11 | 1 << 10), even);
  37     assert_eq!(conv(even << 11 | 1 << 10 | 1), even + 1);
  38     assert_eq!(conv(odd << 11 | 1 << 9), odd);
  39     assert_eq!(conv(even << 11 | 1 << 9), even);
  40     assert_eq!(conv(odd << 11 | 0x7FF), odd + 1);
  41     assert_eq!(conv(even << 11 | 0x7FF), even + 1);
  42     assert_eq!(conv(odd << 11 | 0x3FF), odd);
  43     assert_eq!(conv(even << 11 | 0x3FF), even);
  44 }
  45
  46 #[test]
  47 fn integers_to_f64() {
  48     assert_eq!(fp_to_float::<f64>(Fp { f: 1, e: 0 }), 1.0);
  49     assert_eq!(fp_to_float::<f64>(Fp { f: 42, e: 7 }), (42 << 7) as f64);
  50     assert_eq!(fp_to_float::<f64>(Fp { f: 1 << 20, e: 30 }), (1u64 << 50) as f64);
  51     assert_eq!(fp_to_float::<f64>(Fp { f: 4, e: -3 }), 0.5);
  52 }
  53
  54 const SOME_FLOATS: [f64; 9] = [
  55     0.1f64,
  56     33.568,
  57     42.1e-5,
  58     777.0e9,
  59     1.1111,
  60     0.347997,
  61     9843579834.35892,
  62     12456.0e-150,
  63     54389573.0e-150,
  64 ];
  65
  66 #[test]
  67 fn human_f64_roundtrip() {
  68     for &x in &SOME_FLOATS {
  69         let (f, e, _) = integer_decode(x);
  70         let fp = Fp { f: f, e: e };
  71         assert_eq!(fp_to_float::<f64>(fp), x);
  72     }
  73 }
  74
  75 #[test]
  76 fn rounding_overflow() {
  77     let x = Fp { f: 0xFF_FF_FF_FF_FF_FF_FF_00u64, e: 42 };
  78     let rounded = round_normal::<f64>(x);
  79     let adjusted_k = x.e + 64 - 53;
  80     assert_eq!(rounded.sig, 1 << 52);
  81     assert_eq!(rounded.k, adjusted_k + 1);
  82 }
  83
  84 #[test]
  85 fn prev_float_monotonic() {
  86     let mut x = 1.0;
  87     for _ in 0..100 {
  88         let x1 = prev_float(x);
  89         assert!(x1 < x);
  90         assert!(x - x1 < 1e-15);
  91         x = x1;
  92     }
  93 }
  94
  95 const MIN_SUBNORMAL: f64 = 5e-324;
  96
  97 #[test]
  98 fn next_float_zero() {
  99     let tiny = next_float(0.0);
 100     assert_eq!(tiny, MIN_SUBNORMAL);
 101     assert!(tiny != 0.0);
 102 }
 103
 104 #[test]
 105 fn next_float_subnormal() {
 106     let second = next_float(MIN_SUBNORMAL);
 107     // For subnormals, MIN_SUBNORMAL is the ULP
 108     assert!(second != MIN_SUBNORMAL);
 109     assert!(second > 0.0);
 110     assert_eq!(second - MIN_SUBNORMAL, MIN_SUBNORMAL);
 111 }
 112
 113 #[test]
 114 fn next_float_inf() {
 115     assert_eq!(next_float(f64::MAX), f64::INFINITY);
 116     assert_eq!(next_float(f64::INFINITY), f64::INFINITY);
 117 }
 118
 119 #[test]
 120 fn next_prev_identity() {
 121     for &x in &SOME_FLOATS {
 122         assert_eq!(prev_float(next_float(x)), x);
 123         assert_eq!(prev_float(prev_float(next_float(next_float(x)))), x);
 124         assert_eq!(next_float(prev_float(x)), x);
 125         assert_eq!(next_float(next_float(prev_float(prev_float(x)))), x);
 126     }
 127 }
 128
 129 #[test]
 130 fn next_float_monotonic() {
 131     let mut x = 0.49999999999999;
 132     assert!(x < 0.5);
 133     for _ in 0..200 {
 134         let x1 = next_float(x);
 135         assert!(x1 > x);
 136         assert!(x1 - x < 1e-15, "next_float_monotonic: delta = {:?}", x1 - x);
 137         x = x1;
 138     }
 139     assert!(x > 0.5);
 140 }
 141
 142 #[test]
 143 fn test_f32_integer_decode() {
 144     assert_eq!(3.14159265359f32.integer_decode(), (13176795, -22, 1));
 145     assert_eq!((-8573.5918555f32).integer_decode(), (8779358, -10, -1));
 146     assert_eq!(2f32.powf(100.0).integer_decode(), (8388608, 77, 1));
 147     assert_eq!(0f32.integer_decode(), (0, -150, 1));
 148     assert_eq!((-0f32).integer_decode(), (0, -150, -1));
 149     assert_eq!(f32::INFINITY.integer_decode(), (8388608, 105, 1));
 150     assert_eq!(f32::NEG_INFINITY.integer_decode(), (8388608, 105, -1));
 151
 152     // Ignore the "sign" (quiet / signalling flag) of NAN.
 153     // It can vary between runtime operations and LLVM folding.
 154     let (nan_m, nan_e, _nan_s) = f32::NAN.integer_decode();
 155     assert_eq!((nan_m, nan_e), (12582912, 105));
 156 }
 157
 158 #[test]
 159 fn test_f64_integer_decode() {
 160     assert_eq!(3.14159265359f64.integer_decode(), (7074237752028906, -51, 1));
 161     assert_eq!((-8573.5918555f64).integer_decode(), (4713381968463931, -39, -1));
 162     assert_eq!(2f64.powf(100.0).integer_decode(), (4503599627370496, 48, 1));
 163     assert_eq!(0f64.integer_decode(), (0, -1075, 1));
 164     assert_eq!((-0f64).integer_decode(), (0, -1075, -1));
 165     assert_eq!(f64::INFINITY.integer_decode(), (4503599627370496, 972, 1));
 166     assert_eq!(f64::NEG_INFINITY.integer_decode(), (4503599627370496, 972, -1));
 167
 168     // Ignore the "sign" (quiet / signalling flag) of NAN.
 169     // It can vary between runtime operations and LLVM folding.
 170     let (nan_m, nan_e, _nan_s) = f64::NAN.integer_decode();
 171     assert_eq!((nan_m, nan_e), (6755399441055744, 972));
 172 }