rust/library/core/tests/num/dec2flt/lemire.rs
Alex Huszagh 8752b40369 Changed dec2flt to use the Eisel-Lemire algorithm.
Implementation is based off fast-float-rust, with a few notable changes.

- Some unsafe methods have been removed.
- Safe methods with inherently unsafe functionality have been removed.
- All unsafe functionality is documented and provably safe.
- Extensive documentation has been added for simpler maintenance.
- Inline annotations on internal routines has been removed.
- Fixed Python errors in src/etc/test-float-parse/runtests.py.
- Updated test-float-parse to be a library, to avoid missing rand dependency.
- Added regression tests for #31109 and #31407 in core tests.
- Added regression tests for #31109 and #31407 in ui tests.
- Use the existing slice primitive to simplify shared dec2flt methods
- Remove Miri ignores from dec2flt, due to faster parsing times.

- resolves #85198
- resolves #85214
- resolves #85234
- fixes #31407
- fixes #31109
- fixes #53015
- resolves #68396
- closes https://github.com/aldanor/fast-float-rust/issues/15
2021-07-17 00:30:34 -05:00

54 lines
2.3 KiB
Rust

use core::num::dec2flt::lemire::compute_float;
fn compute_float32(q: i64, w: u64) -> (i32, u64) {
let fp = compute_float::<f32>(q, w);
(fp.e, fp.f)
}
fn compute_float64(q: i64, w: u64) -> (i32, u64) {
let fp = compute_float::<f64>(q, w);
(fp.e, fp.f)
}
#[test]
fn compute_float_f32_rounding() {
// These test near-halfway cases for single-precision floats.
assert_eq!(compute_float32(0, 16777216), (151, 0));
assert_eq!(compute_float32(0, 16777217), (151, 0));
assert_eq!(compute_float32(0, 16777218), (151, 1));
assert_eq!(compute_float32(0, 16777219), (151, 2));
assert_eq!(compute_float32(0, 16777220), (151, 2));
// These are examples of the above tests, with
// digits from the exponent shifted to the mantissa.
assert_eq!(compute_float32(-10, 167772160000000000), (151, 0));
assert_eq!(compute_float32(-10, 167772170000000000), (151, 0));
assert_eq!(compute_float32(-10, 167772180000000000), (151, 1));
// Let's check the lines to see if anything is different in table...
assert_eq!(compute_float32(-10, 167772190000000000), (151, 2));
assert_eq!(compute_float32(-10, 167772200000000000), (151, 2));
}
#[test]
fn compute_float_f64_rounding() {
// These test near-halfway cases for double-precision floats.
assert_eq!(compute_float64(0, 9007199254740992), (1076, 0));
assert_eq!(compute_float64(0, 9007199254740993), (1076, 0));
assert_eq!(compute_float64(0, 9007199254740994), (1076, 1));
assert_eq!(compute_float64(0, 9007199254740995), (1076, 2));
assert_eq!(compute_float64(0, 9007199254740996), (1076, 2));
assert_eq!(compute_float64(0, 18014398509481984), (1077, 0));
assert_eq!(compute_float64(0, 18014398509481986), (1077, 0));
assert_eq!(compute_float64(0, 18014398509481988), (1077, 1));
assert_eq!(compute_float64(0, 18014398509481990), (1077, 2));
assert_eq!(compute_float64(0, 18014398509481992), (1077, 2));
// These are examples of the above tests, with
// digits from the exponent shifted to the mantissa.
assert_eq!(compute_float64(-3, 9007199254740992000), (1076, 0));
assert_eq!(compute_float64(-3, 9007199254740993000), (1076, 0));
assert_eq!(compute_float64(-3, 9007199254740994000), (1076, 1));
assert_eq!(compute_float64(-3, 9007199254740995000), (1076, 2));
assert_eq!(compute_float64(-3, 9007199254740996000), (1076, 2));
}