| use core::num::flt2dec::estimator::*; |
| |
| #[test] |
| fn test_estimate_scaling_factor() { |
| macro_rules! assert_almost_eq { |
| ($actual:expr, $expected:expr) => ({ |
| let actual = $actual; |
| let expected = $expected; |
| println!("{} - {} = {} - {} = {}", stringify!($expected), stringify!($actual), |
| expected, actual, expected - actual); |
| assert!(expected == actual || expected == actual + 1, |
| "expected {}, actual {}", expected, actual); |
| }) |
| } |
| |
| assert_almost_eq!(estimate_scaling_factor(1, 0), 0); |
| assert_almost_eq!(estimate_scaling_factor(2, 0), 1); |
| assert_almost_eq!(estimate_scaling_factor(10, 0), 1); |
| assert_almost_eq!(estimate_scaling_factor(11, 0), 2); |
| assert_almost_eq!(estimate_scaling_factor(100, 0), 2); |
| assert_almost_eq!(estimate_scaling_factor(101, 0), 3); |
| assert_almost_eq!(estimate_scaling_factor(10000000000000000000, 0), 19); |
| assert_almost_eq!(estimate_scaling_factor(10000000000000000001, 0), 20); |
| |
| // 1/2^20 = 0.00000095367... |
| assert_almost_eq!(estimate_scaling_factor(1 * 1048576 / 1000000, -20), -6); |
| assert_almost_eq!(estimate_scaling_factor(1 * 1048576 / 1000000 + 1, -20), -5); |
| assert_almost_eq!(estimate_scaling_factor(10 * 1048576 / 1000000, -20), -5); |
| assert_almost_eq!(estimate_scaling_factor(10 * 1048576 / 1000000 + 1, -20), -4); |
| assert_almost_eq!(estimate_scaling_factor(100 * 1048576 / 1000000, -20), -4); |
| assert_almost_eq!(estimate_scaling_factor(100 * 1048576 / 1000000 + 1, -20), -3); |
| assert_almost_eq!(estimate_scaling_factor(1048575, -20), 0); |
| assert_almost_eq!(estimate_scaling_factor(1048576, -20), 0); |
| assert_almost_eq!(estimate_scaling_factor(1048577, -20), 1); |
| assert_almost_eq!(estimate_scaling_factor(10485759999999999999, -20), 13); |
| assert_almost_eq!(estimate_scaling_factor(10485760000000000000, -20), 13); |
| assert_almost_eq!(estimate_scaling_factor(10485760000000000001, -20), 14); |
| |
| // extreme values: |
| // 2^-1074 = 4.94065... * 10^-324 |
| // (2^53-1) * 2^971 = 1.79763... * 10^308 |
| assert_almost_eq!(estimate_scaling_factor(1, -1074), -323); |
| assert_almost_eq!(estimate_scaling_factor(0x1fffffffffffff, 971), 309); |
| |
| for i in -1074..972 { |
| let expected = super::ldexp_f64(1.0, i).log10().ceil(); |
| assert_almost_eq!(estimate_scaling_factor(1, i as i16), expected as i16); |
| } |
| } |