Eric Coissac
8c7017a99d
- Update obioptions.Version from "Release 4.4.29" to "/v/ Release v5" - Update version.txt from 4.29 → .30 (automated by Makefile)
1.5 KiB
obistats Package: Semantic Overview
The obistats package provides low-level statistical and combinatorial utilities in pure Go, focusing on numerical robustness and performance.
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Sign Function (
mathSign)
Returns the sign of afloat64:-1,0, or+1. Handles NaN by returning NaN. -
Precomputed Factorials (
smallFact)
Precomputes factorials from0!to20!(fits in 64-bit signed integer), enabling fast exact binomial coefficient computation for smalln. -
Binomial Coefficient (
mathChoose)
Computes\binom{n}{k}efficiently:- For
n ≤ 20: uses integer arithmetic (multiplication + division) for exact results. - For larger
n: leverages logarithms viamathLchooseand exponentiates (exp(log(Choose))) to avoid overflow.
- For
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Log-Binomial Coefficient (
mathLchoose)
Computes\log \binom{n}{k}via the log-gamma function:\log \binom{n}{k} = \lg(n+1) - \lg(k+1) - \lg(n-k+1)Ensures numerical stability for large
n, avoiding overflow/underflow. -
Internal Helper (
lchoose)
Core implementation of log-binomial usingmath.Lgamma, reused by both exact and large-scale paths.
Design Notes:
- Prioritizes correctness (e.g., NaN propagation, edge-case handling).
- Balances speed and precision: exact integer arithmetic for small inputs; log-space computation for scalability.
- Mirrors functionality from an internal benchmarking module, adapted here as a standalone utility.