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norm_cdf_poly

solmath::normal

Function norm_cdf_poly 

Source 
pub fn norm_cdf_poly(x: i128) -> Result<i128, SolMathError>
Expand description

Standard normal CDF: Phi(x) at SCALE.

6-piece minimax polynomial + continued-fraction asymptotic tail.

  • x: signed fixed-point at SCALE (1e12).
  • Returns: i128 probability in [0, SCALE_I]. Returns 0 for x < -8SCALE, SCALE_I for x > 8SCALE.
  • Errors: Overflow on internal arithmetic overflow (extremely unlikely).
  • Accuracy: max 4 ULP, 50% exact. Monotone with zero boundary discontinuity.