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Diffstat (limited to 'experiments/integral.c')
-rw-r--r-- | experiments/integral.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/experiments/integral.c b/experiments/integral.c new file mode 100644 index 0000000..46827d9 --- /dev/null +++ b/experiments/integral.c @@ -0,0 +1,113 @@ +#include <complex.h> +#include <math.h> +#include <omp.h> +#include <string.h> + +#include <gsl/gsl_sf.h> +#include <gsl/gsl_blas.h> +#include <gsl/gsl_math.h> +#include <gsl/gsl_poly.h> +#include <gsl/gsl_randist.h> + +#include "extent-sampling.h" +#include "utils.h" + +#define DIMENSION_START 5 +#define DIMENSION_STEP 5 +#define DIMENSION_STOP 100 + +#define RTOLS 3 +#define RTOL1 0.2 +#define RTOL2 0.1 +#define RTOL3 0.05 + +#define MAX_EXTENT 1.0 + +#define POLYNOMIAL_DEGREE 3 +double poly_coeffs[POLYNOMIAL_DEGREE + 1] = {-0.09375, 0.6875, -1.5, 1}; + +typedef double (*true_integral_t) (unsigned int); +gsl_rng* r; + +double uniform_oracle (const gsl_vector* x) { + return gsl_ran_flat(r, 0, MAX_EXTENT); +} + +double polynomial_integrand (double r, const gsl_vector* x) { + return gsl_poly_eval(poly_coeffs, POLYNOMIAL_DEGREE + 1, r); +} + +double polynomial_true_integral (unsigned int n) { + double integrand[POLYNOMIAL_DEGREE + 1]; + for (int k=0; k<=POLYNOMIAL_DEGREE; k++) + integrand[k] = poly_coeffs[k]/(n + k)/(n + k + 1); + return surface_area_of_ball(n) + / MAX_EXTENT + * gsl_pow_uint(MAX_EXTENT, n + 1) + * gsl_poly_eval(integrand, POLYNOMIAL_DEGREE+1, MAX_EXTENT); +} + +double gaussian_integrand (double r, const gsl_vector* x) { + return exp(-gsl_pow_2(r)/2); +} + +double gaussian_true_integral (unsigned int n) { + return pow(2, 0.5*n - 1) + * surface_area_of_ball(n) + / MAX_EXTENT + * (MAX_EXTENT*lower_incomplete_gamma(0.5*n, 0.5*gsl_pow_2(MAX_EXTENT)) + - sqrt(2) * lower_incomplete_gamma(0.5*(n + 1), 0.5*gsl_pow_2(MAX_EXTENT))); +} + +double x_coordinate_integrand (double r, const gsl_vector* x) { + return fabs(r*gsl_vector_get(x, 0)); +} + +double x_coordinate_true_integral (unsigned int n) { + return surface_area_of_ball(n+3) / 2 / (n+2) / gsl_pow_2(M_PI) + * gsl_pow_uint(MAX_EXTENT, n+1) + / MAX_EXTENT; +} + +void run_experiment (integrand_t integrand, extent_oracle_t oracle, true_integral_t true_integral, const char* filename_prefix) +{ + gsl_rstat_workspace* stats = gsl_rstat_alloc(); + printf("dimension\trtol=%g\trtol=%g\trtol=%g\n", RTOL1, RTOL2, RTOL3); + double rtol[RTOLS] = {RTOL1, RTOL2, RTOL3}; + FILE *fp[RTOLS]; + for (int i=0; i<RTOLS; i++) { + char *filename; + asprintf(&filename, "%s-%g.dat", filename_prefix, rtol[i]); + fp[i] = fopen(filename, "w"); + fprintf(fp[i], "dimension\tsamples\n"); + free(filename); + } + for (int dim=DIMENSION_START; dim<=DIMENSION_STOP; dim+=DIMENSION_STEP) { + printf("%d\t", dim); + for (int i=0; i<RTOLS; i++) { + integral(integrand, oracle, true_integral(dim), r, dim, rtol[i], stats); + fprintf(fp[i], "%d\t%zd\n", dim, gsl_rstat_n(stats)); + printf("%zd\t", gsl_rstat_n(stats)); + } + printf("\n"); + gsl_rstat_reset(stats); + } + for (int i=0; i<RTOLS; i++) fclose(fp[i]); + gsl_rstat_free(stats); +} + +int main (int argc, char** argv) +{ + gsl_rng_env_setup(); + r = gsl_rng_alloc(gsl_rng_default); + + printf("# polynomial\n"); + run_experiment(polynomial_integrand, uniform_oracle, polynomial_true_integral, "integral-polynomial"); + printf("# gaussian\n"); + run_experiment(gaussian_integrand, uniform_oracle, gaussian_true_integral, "integral-gaussian"); + printf("# x-coordinate\n"); + run_experiment(x_coordinate_integrand, uniform_oracle, x_coordinate_true_integral, "integral-x-coordinate"); + + gsl_rng_free(r); + return 0; +} |