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Diffstat (limited to '')
-rw-r--r-- | library/core/tests/num/flt2dec/estimator.rs | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/library/core/tests/num/flt2dec/estimator.rs b/library/core/tests/num/flt2dec/estimator.rs new file mode 100644 index 000000000..da203b5f3 --- /dev/null +++ b/library/core/tests/num/flt2dec/estimator.rs @@ -0,0 +1,62 @@ +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); + + // Miri is too slow + let step = if cfg!(miri) { 37 } else { 1 }; + + for i in (-1074..972).step_by(step) { + let expected = super::ldexp_f64(1.0, i).log10().ceil(); + assert_almost_eq!(estimate_scaling_factor(1, i as i16), expected as i16); + } +} |