egutierrez
d115d8e830
Nuevo dominio cpp/functions/datascience con primitivas puras CPU para post- proceso de samples Monte Carlo y diagnostico de cadenas MCMC. Diseñadas como gemelas CPU de los kernels GPU (rng pareja con gpu_rng_glsl, MH 1D/ND con mc_metropolis_hastings_gpu) para validar numericamente y para datasets pequeños donde el dispatch GPU no compensa. - rng: xoshiro256++ con uniform / normal (Box-Muller) / below (Lemire) / categorical. Determinista bit-exacto dado seed. - stats_summary: sum (Kahan), mean, var/std (Welford one-pass), min, max, quantile / percentile (R type-7). - autocorr: r(k), ACF, tau_int (Sokal) — diagnostico ACF y ESS. - rhat_ess: Gelman-Rubin clasico y split + ESS basico (multi-chain). - beta_dist: lgamma (Lanczos), beta_pdf, beta_cdf (continued fraction), beta_quantile, mean/var/std — para inferencia Beta-Binomial. - drawdown: max_dd absoluto/pct + underwater series para sesiones simuladas y backtests. - samples_to_grid_2d: binning 2D CPU para alimentar heatmap_cpp_viz / contour_cpp_viz desde samples (x[], y[]). - metropolis_hastings: MH 1D y ND con target log-pdf como std::function (no normalizada). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
97 lines
3.0 KiB
C++
97 lines
3.0 KiB
C++
#include "datascience/metropolis_hastings.h"
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#include <cmath>
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#include <vector>
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namespace fn::ds {
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MHResult mh_run_1d(const std::function<double(double)>& target_log_pdf,
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double x0,
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double proposal_sigma,
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std::size_t n_samples,
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double* out_chain,
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Rng& r) {
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MHResult res{};
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if (n_samples == 0 || out_chain == nullptr) return res;
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out_chain[0] = x0;
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double curr = x0;
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double log_p_curr = target_log_pdf(curr);
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std::size_t accepted = 0;
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for (std::size_t i = 1; i < n_samples; ++i) {
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double prop = curr + proposal_sigma * rng_normal(r);
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double log_p_prop = target_log_pdf(prop);
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double log_alpha = log_p_prop - log_p_curr;
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bool accept = false;
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if (log_alpha >= 0.0) {
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accept = true;
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} else {
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double u = rng_uniform(r);
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if (u < std::exp(log_alpha)) accept = true;
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}
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if (accept) {
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curr = prop;
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log_p_curr = log_p_prop;
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++accepted;
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}
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out_chain[i] = curr;
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}
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res.n_samples = n_samples;
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res.n_accepted = accepted;
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res.accept_rate = (n_samples > 1)
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? static_cast<double>(accepted) / static_cast<double>(n_samples - 1)
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: 0.0;
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return res;
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}
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MHResult mh_run_nd(const std::function<double(const double*)>& target_log_pdf,
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const double* x0,
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const double* proposal_sigma,
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int d,
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std::size_t n_samples,
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double* out_chain,
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Rng& r) {
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MHResult res{};
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if (d <= 0 || n_samples == 0 || out_chain == nullptr ||
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x0 == nullptr || proposal_sigma == nullptr) return res;
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std::vector<double> curr(d);
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std::vector<double> prop(d);
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for (int k = 0; k < d; ++k) curr[k] = x0[k];
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for (int k = 0; k < d; ++k) out_chain[k] = curr[k];
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double log_p_curr = target_log_pdf(curr.data());
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std::size_t accepted = 0;
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for (std::size_t i = 1; i < n_samples; ++i) {
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for (int k = 0; k < d; ++k) {
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prop[k] = curr[k] + proposal_sigma[k] * rng_normal(r);
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}
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double log_p_prop = target_log_pdf(prop.data());
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double log_alpha = log_p_prop - log_p_curr;
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bool accept = false;
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if (log_alpha >= 0.0) {
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accept = true;
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} else {
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double u = rng_uniform(r);
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if (u < std::exp(log_alpha)) accept = true;
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}
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if (accept) {
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for (int k = 0; k < d; ++k) curr[k] = prop[k];
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log_p_curr = log_p_prop;
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++accepted;
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}
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for (int k = 0; k < d; ++k) {
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out_chain[i * static_cast<std::size_t>(d) + k] = curr[k];
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}
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}
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res.n_samples = n_samples;
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res.n_accepted = accepted;
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res.accept_rate = (n_samples > 1)
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? static_cast<double>(accepted) / static_cast<double>(n_samples - 1)
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: 0.0;
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return res;
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}
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} // namespace fn::ds
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