public static void dream_algm(int chain_num, int cr_num, double[] fit, int gen_num,
double[] gr, ref bool gr_conv, ref int gr_count, int gr_num, double gr_threshold,
double[] jumprate_table, int jumpstep, double[] limits, int pair_num,
int par_num, int printstep,
Func <int, double[], int, DensityResult> prior_density,
Func <int, double[], double> sample_likelihood,
ref double[] z)
//****************************************************************************80
//
// Purpose:
//
// DREAM_ALGM gets a candidate parameter sample.
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 25 May 2013
//
// Author:
//
// Original FORTRAN90 version by Guannan Zhang.
// C++ version by John Burkardt.
//
// Reference:
//
// Jasper Vrugt, CJF ter Braak, CGH Diks, Bruce Robinson, James Hyman,
// Dave Higdon,
// Accelerating Markov Chain Monte Carlo Simulation by Differential
// Evolution with Self-Adaptive Randomized Subspace Sampling,
// International Journal of Nonlinear Sciences and Numerical Simulation,
// Volume 10, Number 3, March 2009, pages 271-288.
//
// Parameters:
//
// Input, int CHAIN_NUM, the total number of chains.
// 3 <= CHAIN_NUM.
//
// Input, int CR_NUM, the total number of CR values.
// 1 <= CR_NUM.
//
// Input, double FIT[CHAIN_NUM*GEN_NUM], the likelihood of
// each sample.
//
// Input, int GEN_NUM, the total number of generations.
// 2 <= GEN_NUM.
//
// Input, double GR[PAR_NUM*GR_NUM],
// the Gelman-Rubin R statistic.
//
// Input/output, int &GR_CONV, the Gelman-Rubin convergence flag.
//
// Input/output, int &GR_COUNT, counts the number of generations
// at which the Gelman-Rubin statistic has been computed.
//
// Input, int GR_NUM, the number of times the Gelman-Rubin
// statistic may be computed.
//
// Input, double GR_THRESHOLD, the convergence tolerance for
// the Gelman-Rubin statistic.
//
// Input, double JUMPRATE_TABLE[PAR_NUM], the jumprate table.
//
// Input, int JUMPSTEP, forces a "long jump" every
// JUMPSTEP generations.
//
// Input, double LIMITS[2*PAR_NUM], lower and upper bounds
// for each parameter.
//
// Input, int PAIR_NUM, the number of pairs of
// crossover chains.
// 0 <= PAIR_NUM.
//
// Input, int PAR_NUM, the total number of parameters.
// 1 <= PAR_NUM.
//
// Input, int PRINTSTEP, the interval between generations on
// which the Gelman-Rubin statistic will be computed and written to a file.
//
// Input/output, double Z[PAR_NUM*CHAIN_NUM*GEN_NUM], the Markov chain
// sample data.
//
// Local parameters:
//
// Local, int CHAIN_INDEX, the index of the current chain.
// 1 <= CHAIN_INDEX <= CHAIN_NUM.
//
// Local, double CR[CR_NUM], the CR values.
//
// Local, double CR_DIS[CR_NUM], the CR distances.
//
// Local, int CR_INDEX, the index of the selected CR value.
// 1 <= CR_INDEX <= CR_NUM.
//
// Local, double CR_PROB[CR_NUM], the probability of each CR.
//
// Local, double CR_UPS[CR_NUM], the number of updates for each CR.
//
// Local, int GEN_INDEX, the index of the current generation.
// 1 <= GEN_INDEX <= GEN_NUM.
//
// Local, double ZP[PAR_NUM], a candidate sample.
//
// Local, int ZP_ACCEPT, the number of candidates accepted.
//
// Local, double ZP_ACCEPT_RATE, the rate at which generated
// candidates were accepted.
//
// Local, int ZP_COUNT, the number of candidates generated.
//
// Local, double ZP_RATIO, the Metropolis ratio for a candidate.
//
{
int gen_index;
double[] zp_old = new double[par_num];
int zp_count = 0;
int zp_accept = 0;
//
// Initialize the CR values.
//
double[] cr = new double[cr_num];
double[] cr_dis = new double[cr_num];
double[] cr_prob = new double[cr_num];
int[] cr_ups = new int[cr_num];
CR.cr_init(ref cr, ref cr_dis, cr_num, ref cr_prob, ref cr_ups);
for (gen_index = 1; gen_index < gen_num; gen_index++)
{
int chain_index;
for (chain_index = 0; chain_index < chain_num; chain_index++)
{
//
// Choose CR_INDEX, the index of a CR.
//
int cr_index = CR.cr_index_choose(cr_num, cr_prob);
//
// Generate a sample candidate ZP.
//
double[] zp = Sample.sample_candidate(chain_index, chain_num, cr, cr_index, cr_num,
gen_index, gen_num, jumprate_table, jumpstep, limits, pair_num,
par_num, z);
zp_count += 1;
//
// Compute the log likelihood function for ZP.
//
double zp_fit = sample_likelihood(par_num, zp);
int i;
for (i = 0; i < par_num; i++)
{
zp_old[i] = z[i + chain_index * par_num + (gen_index - 1) * par_num * chain_num];
}
double zp_old_fit = fit[chain_index + (gen_index - 1) * chain_num];
//
// Compute the Metropolis ratio for ZP.
//
double pd1 = prior_density(par_num, zp, 0).result;
double pd2 = prior_density(par_num,
z, +0 + chain_index * par_num + (gen_index - 1) * par_num * chain_num).result;
double zp_ratio = Math.Exp(
zp_fit + Math.Log(pd1) -
(zp_old_fit + Math.Log(pd2)));
zp_ratio = Math.Min(zp_ratio, 1.0);
//
// Accept the candidate, or copy the value from the previous generation.
//
double r = PDF.r8_uniform_01_sample();
if (r <= zp_ratio)
{
for (i = 0; i < par_num; i++)
{
z[i + chain_index * par_num + gen_index * par_num * chain_num] = zp[i];
}
zp_accept += 1;
fit[chain_index + gen_index * chain_num] = zp_fit;
}
else
{
for (i = 0; i < par_num; i++)
{
z[i + chain_index * par_num + gen_index * par_num * chain_num] = zp_old[i];
}
fit[chain_index + gen_index * chain_num] = zp_old_fit;
}
switch (gr_conv)
{
//
// Update the CR distance.
//
case false:
{
switch (cr_num)
{
case > 1:
CR.cr_dis_update(chain_index, chain_num, ref cr_dis, cr_index,
cr_num, ref cr_ups, gen_index, gen_num, par_num, z);
break;
}
break;
}
}
}
switch (gr_conv)
{
//
// Update the multinomial distribution of CR.
//
case false:
{
switch (cr_num)
{
case > 1:
{
switch ((gen_index + 1) % 10)
{
case 0:
CR.cr_prob_update(cr_dis, cr_num, ref cr_prob, cr_ups);
break;
}
break;
}
}
break;
}
}
switch ((gen_index + 1) % printstep)
{
//
// Every PRINTSTEP interval,
// * compute the Gelman Rubin R statistic for this generation,
// and determine if convergence has occurred.
//
case 0:
GelmanRubin.gr_compute(chain_num, gen_index, gen_num, ref gr, ref gr_conv, ref gr_count,
gr_num, gr_threshold, par_num, z);
break;
}
switch (gr_conv)
{
//
// Check for outlier chains.
//
case false:
{
switch ((gen_index + 1) % 10)
{
case 0:
Chain.chain_outliers(chain_num, gen_index, gen_num, par_num, fit, z);
break;
}
break;
}
}
}
//
// Compute the acceptance rate.
//
double zp_accept_rate = zp_accept / (double)zp_count;
Console.WriteLine("");
Console.WriteLine(" The acceptance rate is " + zp_accept_rate + "");
}
