Commit 72127be9 authored by Matthieu Schaller's avatar Matthieu Schaller
Browse files

Documentation and missing file.

parent 7f52855a
/*******************************************************************************
* This file is part of SWIFT.
* Copyright (c) 2017 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
******************************************************************************/
/* Config parameters. */
#include "../config.h"
/* This object's header. */
#include "gravity.h"
/* Local headers. */
#include "active.h"
#include "error.h"
/**
* @brief Run a brute-force gravity calculation for a subset of particles.
*
* All gpart with ID modulo SWIFT_GRAVITY_FORCE_CHECKS will get their forces
* computed.
*
* @param s The #space to use.
* @param e The #engine (to access the current time).
*/
void gravity_exact_force_compute(struct space *s, const struct engine *e) {
#ifdef SWIFT_GRAVITY_FORCE_CHECKS
const ticks tic = getticks();
const double const_G = e->physical_constants->const_newton_G;
int counter = 0;
for (size_t i = 0; i < s->nr_gparts; ++i) {
struct gpart *gpi = &s->gparts[i];
/* Is the particle active and part of the subset to be tested ? */
if (gpi->id_or_neg_offset % SWIFT_GRAVITY_FORCE_CHECKS == 0 &&
gpart_is_active(gpi, e)) {
/* Be ready for the calculation */
gpi->a_grav[0] = 0.f;
gpi->a_grav[1] = 0.f;
gpi->a_grav[2] = 0.f;
/* Interact it with all other particles in the space.*/
for (size_t j = 0; j < s->nr_gparts; ++j) {
/* No self interaction */
if (i == j) continue;
struct gpart *gpj = &s->gparts[j];
/* Compute the pairwise distance. */
float dx[3] = {gpi->x[0] - gpj->x[0], // x
gpi->x[1] - gpj->x[1], // y
gpi->x[2] - gpj->x[2]}; // z
const float r2 = dx[0] * dx[0] + dx[1] * dx[1] + dx[2] * dx[2];
runner_iact_grav_pp_nonsym(0.f, r2, dx, gpi, gpj);
}
/* Finish the calculation */
gravity_end_force(gpi, const_G);
/* Store the exact answer */
gpi->a_grav_exact[0] = gpi->a_grav[0];
gpi->a_grav_exact[1] = gpi->a_grav[1];
gpi->a_grav_exact[2] = gpi->a_grav[2];
/* Restore everything */
gpi->a_grav[0] = 0.f;
gpi->a_grav[1] = 0.f;
gpi->a_grav[2] = 0.f;
counter++;
}
}
message("Computed exact gravity for %d gparts.", counter);
if (e->verbose)
message("took %.3f %s.", clocks_from_ticks(getticks() - tic),
clocks_getunit());
#else
error("Gravity checking function called without the corresponding flag.");
#endif
}
/**
* @brief Check the accuracy of the gravity calculation by comparing the
* accelerations
* to the brute-force computed ones.
*
* All gpart with ID modulo SWIFT_GRAVITY_FORCE_CHECKS will be checked.
*
* @param s The #space to use.
* @param e The #engine (to access the current time).
* @param rel_tol The maximal relative error. Will call error() if one particle
* has a larger error.
*/
void gravity_exact_force_check(struct space *s, const struct engine *e,
float rel_tol) {
#ifdef SWIFT_GRAVITY_FORCE_CHECKS
const double const_G = e->physical_constants->const_newton_G;
int counter = 0;
/* Some accumulators */
float err_rel[3];
float err_rel_max[3] = {0.f, 0.f, 0.f};
float err_rel_min[3] = {FLT_MAX, FLT_MAX, FLT_MAX};
float err_rel_mean[3] = {0.f, 0.f, 0.f};
float err_rel_mean2[3] = {0.f, 0.f, 0.f};
float err_rel_std[3] = {0.f, 0.f, 0.f};
for (size_t i = 0; i < s->nr_gparts; ++i) {
struct gpart *gpi = &s->gparts[i];
/* Is the particle was active and part of the subset to be tested ? */
if (gpi->id_or_neg_offset % SWIFT_GRAVITY_FORCE_CHECKS == 0 &&
gpart_is_starting(gpi, e)) {
/* Compute relative error */
for (int k = 0; k < 3; ++k)
if (fabsf(gpi->a_grav_exact[k]) > FLT_EPSILON * const_G)
err_rel[k] = (gpi->a_grav[k] - gpi->a_grav_exact[k]) /
fabsf(gpi->a_grav_exact[k]);
else
err_rel[k] = 0.f;
/* Check that we are not above tolerance */
if (fabsf(err_rel[0]) > rel_tol || fabsf(err_rel[1]) > rel_tol ||
fabsf(err_rel[2]) > rel_tol)
error("Error too large ! gp->a_grav=[%e %e %e] gp->a_exact=[%e %e %e]",
gpi->a_grav[0], gpi->a_grav[1], gpi->a_grav[2],
gpi->a_grav_exact[0], gpi->a_grav_exact[1], gpi->a_grav_exact[2]);
/* Construct some statistics */
for (int k = 0; k < 3; ++k) {
err_rel_max[k] = max(err_rel_max[k], fabsf(err_rel[k]));
err_rel_min[k] = min(err_rel_min[k], fabsf(err_rel[k]));
err_rel_mean[k] += err_rel[k];
err_rel_mean2[k] += err_rel[k] * err_rel[k];
}
counter++;
}
}
/* Final operation on the stats */
if (counter > 0) {
for (int k = 0; k < 3; ++k) {
err_rel_mean[k] /= counter;
err_rel_mean2[k] /= counter;
err_rel_std[k] =
sqrtf(err_rel_mean2[k] - err_rel_mean[k] * err_rel_mean[k]);
}
}
/* Report on the findings */
message("Checked gravity for %d gparts.", counter);
for (int k = 0; k < 3; ++k)
message("Error on a_grav[%d]: min=%e max=%e mean=%e std=%e", k,
err_rel_min[k], err_rel_max[k], err_rel_mean[k], err_rel_std[k]);
#else
error("Gravity checking function called without the corresponding flag.");
#endif
}
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment