pymath

0 ULP (bit-exact) compatibility with CPython's math and cmath modules.

Every function produces identical results to Python at the binary representation level - not just "close enough", but exactly the same bits.

Overview

pymath is a strict port of CPython's math library to Rust. Each function has been carefully translated from CPython's C implementation, preserving the same algorithms, constants, and corner case handling.

Compatibility Status

math (55/55)

• ceil
• copysign
• fabs
• floor
• fmod
• frexp
• isclose
• isfinite
• isinf
• isnan
• ldexp
• modf
• nextafter
• remainder
• trunc
• ulp
• cbrt
• exp
• exp2
• expm1
• log
• log10
• log1p
• log2
• pow
• sqrt
• acos
• acosh
• asin
• asinh
• atan
• atan2
• atanh
• cos
• cosh
• sin
• sinh
• tan
• tanh
• erf
• erfc
• gamma
• lgamma
• dist
• fsum
• hypot
• prod
• sumprod
• degrees
• radians
• pi
• e
• tau
• inf
• nan

math.integer (6/6, requires num-bigint or malachite-bigint feature)

• comb
• factorial
• gcd
• isqrt
• lcm
• perm

cmath (24/24, requires complex feature)

• abs
• isclose
• isfinite
• isinf
• isnan
• phase
• polar
• rect
• exp
• log
• log10
• sqrt
• acos
• acosh
• asin
• asinh
• atan
• atanh
• cos
• cosh
• sin
• sinh
• tan
• tanh

Usage

use pymath::math::{sqrt, gamma, lgamma};

fn main() {
    let sqrt_result = sqrt(2.0).unwrap();
    let gamma_result = gamma(4.5).unwrap();
    let lgamma_result = lgamma(4.5).unwrap();
}

Bit-exact verification

# Python 3.14
>>> import math
>>> math.gamma(0.5).hex()
'0x1.c5bf891b4ef6ap+0'

// Rust - identical bits
assert_eq!(
    pymath::math::gamma(0.5).unwrap().to_bits(),
    0x3ffc5bf891b4ef6a
);

Bit representation may vary across platforms, but CPython and pymath built on the same environment will always produce identical results.

Features

• complex (default) - Enable cmath module for complex number functions
• num-bigint - Enable integer functions using num-bigint
• malachite-bigint - Enable integer functions using malachite-bigint
• mul_add - Use hardware FMA for bit-exact macOS compatibility

Module Structure

• pymath::math - Real number math functions (Python's math module)
• pymath::cmath - Complex number functions (Python's cmath module)
• pymath::m - Direct libm bindings