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#![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);
}
}
}
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