mirror of
https://github.com/c3lang/c3c.git
synced 2026-02-27 12:01:16 +00:00
8bb974829d
* math: implement discrete and continuous distributions Implement a comprehensive set of continuous and discrete probability distributions with support for PDF, CDF, inverse CDF, random sampling, mean, and variance calculations. The following distributions are implemented: * Normal * Uniform * Exponential * Chi-Squared * F-Distribution * Student t * Binomial * Poisson * update releasenotes.md * Formatting --------- Co-authored-by: Christoffer Lerno <christoffer@aegik.com>
78 lines
1.9 KiB
Plaintext
78 lines
1.9 KiB
Plaintext
module std::math::nolibc @if(env::NO_LIBC || $feature(C3_MATH));
|
|
|
|
<*
|
|
Error function for float.
|
|
*>
|
|
fn float _erff(float x)
|
|
{
|
|
// Handle special cases.
|
|
if (x == 0.0) return 0.0;
|
|
if (x == float.inf) return 1.0;
|
|
if (x == -float.inf) return -1.0;
|
|
|
|
// Use symmetry: erf(-x) = -erf(x)
|
|
float sign = 1.0;
|
|
if (x < 0.0)
|
|
{
|
|
x = -x;
|
|
sign = -1.0;
|
|
}
|
|
|
|
const float P1 = 0.4067420160f;
|
|
const float P2 = 0.0072279182f;
|
|
const float A1 = 0.3168798904f;
|
|
const float A2 = -0.1383293141f;
|
|
const float A3 = 1.0868083034f;
|
|
const float A4 = -1.1169415512f;
|
|
const float A5 = 1.2064490307f;
|
|
const float A6 = -0.3931277152f;
|
|
const float A7 = 0.0382613542f;
|
|
|
|
float t = 1.0f / (1.0f + P1 * x + P2 * x * x);
|
|
float t2 = t * t;
|
|
float sum = A1 * t + A2 * t2 + A3 * t2 * t + A4 * t2 * t2;
|
|
sum += A5 * t2 * t2 * t + A6 * t2 * t2 * t2 + A7 * t2 * t2 * t2 * t;
|
|
|
|
// For intermediate x, use continued fraction.
|
|
return sign * (1.0f - sum * math::exp(-x * x));
|
|
}
|
|
|
|
<*
|
|
Error function for double.
|
|
*>
|
|
fn double _erf(double x)
|
|
{
|
|
// Handle special cases.
|
|
if (x == 0.0) return 0.0;
|
|
if (x == double.inf) return 1.0;
|
|
if (x == -double.inf) return -1.0;
|
|
|
|
// Use symmetry: erf(-x) = -erf(x)
|
|
double sign = 1.0;
|
|
if (x < 0.0)
|
|
{
|
|
x = -x;
|
|
sign = -1.0;
|
|
}
|
|
|
|
const double P1 = 0.406742016006509;
|
|
const double P2 = 0.0072279182302319;
|
|
const double A1 = 0.316879890481381;
|
|
const double A2 = -0.138329314150635;
|
|
const double A3 = 1.08680830347054;
|
|
const double A4 = -1.11694155120396;
|
|
const double A5 = 1.20644903073232;
|
|
const double A6 = -0.393127715207728;
|
|
const double A7 = 0.0382613542530727;
|
|
|
|
double t = 1.0 / (1.0 + P1 * x + P2 * x * x);
|
|
double t2 = t * t;
|
|
double sum = A1 * t + A2 * t2 + A3 * t2 * t + A4 * t2 * t2;
|
|
sum += A5 * t2 * t2 * t + A6 * t2 * t2 * t2 + A7 * t2 * t2 * t2 * t;
|
|
|
|
// For intermediate x, use continued fraction.
|
|
return sign * (1.0 - sum * math::exp(-x * x));
|
|
}
|
|
|
|
|