| #![allow(unreachable_code)] |
| use core::f64; |
| |
| const TOINT: f64 = 1. / f64::EPSILON; |
| |
| /// Ceil (f64) |
| /// |
| /// Finds the nearest integer greater than or equal to `x`. |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub fn ceil(x: f64) -> f64 { |
| // On wasm32 we know that LLVM's intrinsic will compile to an optimized |
| // `f64.ceil` native instruction, so we can leverage this for both code size |
| // and speed. |
| llvm_intrinsically_optimized! { |
| #[cfg(target_arch = "wasm32")] { |
| return unsafe { ::core::intrinsics::ceilf64(x) } |
| } |
| } |
| #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))] |
| { |
| //use an alternative implementation on x86, because the |
| //main implementation fails with the x87 FPU used by |
| //debian i386, probablly due to excess precision issues. |
| //basic implementation taken from https://github.com/rust-lang/libm/issues/219 |
| use super::fabs; |
| if fabs(x).to_bits() < 4503599627370496.0_f64.to_bits() { |
| let truncated = x as i64 as f64; |
| if truncated < x { |
| return truncated + 1.0; |
| } else { |
| return truncated; |
| } |
| } else { |
| return x; |
| } |
| } |
| let u: u64 = x.to_bits(); |
| let e: i64 = (u >> 52 & 0x7ff) as i64; |
| let y: f64; |
| |
| if e >= 0x3ff + 52 || x == 0. { |
| return x; |
| } |
| // y = int(x) - x, where int(x) is an integer neighbor of x |
| y = if (u >> 63) != 0 { |
| x - TOINT + TOINT - x |
| } else { |
| x + TOINT - TOINT - x |
| }; |
| // special case because of non-nearest rounding modes |
| if e < 0x3ff { |
| force_eval!(y); |
| return if (u >> 63) != 0 { -0. } else { 1. }; |
| } |
| if y < 0. { |
| x + y + 1. |
| } else { |
| x + y |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| use core::f64::*; |
| |
| #[test] |
| fn sanity_check() { |
| assert_eq!(ceil(1.1), 2.0); |
| assert_eq!(ceil(2.9), 3.0); |
| } |
| |
| /// The spec: https://en.cppreference.com/w/cpp/numeric/math/ceil |
| #[test] |
| fn spec_tests() { |
| // Not Asserted: that the current rounding mode has no effect. |
| assert!(ceil(NAN).is_nan()); |
| for f in [0.0, -0.0, INFINITY, NEG_INFINITY].iter().copied() { |
| assert_eq!(ceil(f), f); |
| } |
| } |
| } |