Commit 47bfee49 authored by rttw52's avatar rttw52

Sorry I messed up the git so it's one big commit.

Updated RTD as per your recomendations.

Added ForceChecks to paramater_example.yml

Changed brute_force_gravity_flag to force_checks_snapshot_flag

Removed epsilon from gravity_exact_force_file_exits

Made functions in src/kernel_long_gravity.h double
parent c445930d
......@@ -53,8 +53,8 @@ simply the Newtonian sum, i.e.,
To run SWIFT in this mode, configure the code with
``--enable-gravity-force-checks=N``, which means that the exact forces will be
computed for every :math:`N^{th}` particle (i.e., to compute the exact forces
for all particles set ``N=1``).
computed for every :math:`N^{th}` particle based on their ID (i.e., to compute
the exact forces for all particles set ``N=1``).
Two `.dat` files will be output during each timestep, one containing the forces
(really it is the accelerations that are stored) as computed by ``_swift_``, and
......@@ -66,5 +66,8 @@ the number of particles contributing to each force component is also stored
(these numbers will add up to :math:`n-1`).
This mode will slow down the code *considerably*, and it is not recommended to
run on problems with more than :math:`10^{5}` particles. This mode must be run
on a single node/rank and is only designed for pure gravity tests (i.e., DMO).
be run on problems with more than :math:`10^{5}` particles when
``--enable-gravity-force-checks=1``. For larger runs, sampling a sub-set of
particles via the argument ``N`` of the configuration option is recommended.
This mode must be run on a single node/rank, and is primarily designed for pure
gravity tests (i.e., DMO).
......@@ -1258,19 +1258,20 @@ Showing all the parameters for a basic cosmologica test-case, one would have:
Gravity Force Checks
--------------------
By default, when configured with ``--enable-gravity-force-checks`` the "exact"
forces will be computed for all active particles during each timestep.
By default, when the code is configured with ``--enable-gravity-force-checks``,
the "exact" forces of all active gparts are computed during each timestep.
To give a bit more control over this, you can select to only compute the exact
forces during the timesteps that all the particles are active, and/or only at
the timesteps when a snapshot is being dumped, i.e.,
To give a bit more control over this, you can select to only perform the exact
force computation during the timesteps that all gparts are active, and/or only
at the timesteps when a snapshot is being dumped, i.e.,
.. code:: YAML
ForceChecks:
only_when_all_active: 1 # Only compute exact forces during timesteps when all particles are active.
only_when_all_active: 1 # Only compute exact forces during timesteps when all gparts are active.
only_at_snapshots: 1 # Only compute exact forces during timesteps when a snapshot is being dumped.
Note that if ``only_when_all_active:1`` and ``only_when_all_active:1``, the
exact forces will be computed during the first timestep after the snapshot
output time when all particles are active.
If ``only_when_all_active:1`` and ``only_when_all_active:1`` are enabled
together, and all the gparts are not active during the timestep of the snapshot
dump, the exact forces computation is performed on the first timestep at which
all the gparts are active after that snapshot output timestep.
......@@ -77,7 +77,11 @@ Gravity:
dithering: 1 # (Optional) Activate the dithering of the gravity mesh at every rebuild (this is the default value).
dithering_ratio: 1.0 # (Optional) Magnitude of each component of the dithering vector in units of the top-level cell sizes (this is the default value).
# Parameters for the Friends-Of-Friends algorithm
# Parameters when running with SWIFT_GRAVITY_FORCE_CHECKS
ForceChecks:
only_when_all_active: 1 # (Optional) Only compute exact forces during timesteps when all gparts are active (default: 0).
only_at_snapshots: 1 # (Optional) Only compute exact forces during timesteps when a snapshot is being dumped (default: 0).
FOF:
basename: fof_output # Filename for the FOF outputs (Unused when FoF is only run to seed BHs).
scale_factor_first: 0.91 # Scale-factor of first FoF black hole seeding calls (needed for cosmological runs).
......
......@@ -2165,7 +2165,7 @@ void engine_init_particles(struct engine *e, int flag_entropy_ICs,
e->wallclock_time = (float)clocks_diff(&time1, &time2);
#ifdef SWIFT_GRAVITY_FORCE_CHECKS
e->brute_force_gravity_flag = 0;
e->force_checks_snapshot_flag = 0;
#endif
if (e->verbose) message("took %.3f %s.", e->wallclock_time, clocks_getunit());
......@@ -2362,12 +2362,13 @@ void engine_step(struct engine *e) {
if ((e->all_gparts_active && e->force_checks_only_all_active) ||
!e->force_checks_only_all_active) {
/* Is this a snapshot timestep (and the option is selected)? */
if ((e->brute_force_gravity_flag == 1 &&
e->force_checks_only_at_snapshots) ||
!e->force_checks_only_at_snapshots) {
/* Do checks */
gravity_exact_force_compute(e->s, e);
if ((e->force_checks_snapshot_flag &&
e->force_checks_only_at_snapshots) ||
!e->force_checks_only_at_snapshots) {
/* Do checks */
gravity_exact_force_compute(e->s, e);
}
}
}
}
......@@ -2395,15 +2396,16 @@ void engine_step(struct engine *e) {
if ((e->all_gparts_active && e->force_checks_only_all_active) ||
!e->force_checks_only_all_active) {
/* Is this a snapshot timestep (and the option is selected)? */
if ((e->brute_force_gravity_flag == 1 &&
e->force_checks_only_at_snapshots) ||
!e->force_checks_only_at_snapshots) {
/* Do checks */
gravity_exact_force_check(e->s, e, 1e-1);
/* Reset flag waiting for next output time */
e->brute_force_gravity_flag = 0;
if ((e->force_checks_snapshot_flag &&
e->force_checks_only_at_snapshots) ||
!e->force_checks_only_at_snapshots) {
/* Do checks */
gravity_exact_force_check(e->s, e, 1e-1);
/* Reset flag waiting for next output time */
e->force_checks_snapshot_flag = 0;
}
}
}
}
......@@ -2535,7 +2537,7 @@ void engine_check_for_dumps(struct engine *e) {
#ifdef SWIFT_GRAVITY_FORCE_CHECKS
/* Indicate we are allowed to do a brute force calculation now */
e->brute_force_gravity_flag = 1;
e->force_checks_snapshot_flag = 1;
#endif
/* Do we want a corresponding VELOCIraptor output? */
......
......@@ -495,8 +495,8 @@ struct engine {
/* Are all gparts active this timestep? */
int all_gparts_active;
/* Are we doing brute force calculations this timestep? */
int brute_force_gravity_flag;
/* Flag to tell brute force checks a snapshot was recently written. */
int force_checks_snapshot_flag;
#endif
};
......
......@@ -430,7 +430,7 @@ int gravity_exact_force_file_exits(const struct engine *e) {
char line[100];
char dummy1[10], dummy2[10];
double epsilon, newton_G;
double newton_G;
int N, periodic;
/* Reads file header */
if (fgets(line, 100, file) != line) error("Problem reading title");
......@@ -438,17 +438,12 @@ int gravity_exact_force_file_exits(const struct engine *e) {
sscanf(line, "%s %s %le", dummy1, dummy2, &newton_G);
if (fgets(line, 100, file) != line) error("Problem reading N");
sscanf(line, "%s %s %d", dummy1, dummy2, &N);
if (fgets(line, 100, file) != line) error("Problem reading epsilon");
sscanf(line, "%s %s %le", dummy1, dummy2, &epsilon);
if (fgets(line, 100, file) != line) error("Problem reading BC");
sscanf(line, "%s %s %d", dummy1, dummy2, &periodic);
fclose(file);
/* Check whether it matches the current parameters */
if (N == SWIFT_GRAVITY_FORCE_CHECKS && periodic == e->s->periodic &&
(fabs(epsilon - gravity_get_softening(0, e->gravity_properties)) /
epsilon <
1e-5) &&
(fabs(newton_G - e->physical_constants->const_newton_G) / newton_G <
1e-5)) {
return 1;
......
......@@ -222,25 +222,25 @@ kernel_long_grav_force_eval_double(const double u, double *const W) {
const double one_over_sqrt_pi = ((double)(M_2_SQRTPI * 0.5));
const double arg1 = u * 0.5f;
const double arg2 = -arg1 * arg1;
const double arg1 = u * 0.5;
const double arg2 = -arg1 * arg1;
const double term1 = approx_erfcf(arg1);
const double term2 = u * one_over_sqrt_pi * expf(arg2);
const double term1 = erfc(arg1);
const double term2 = u * one_over_sqrt_pi * exp(arg2);
*W = term1 + term2;
#else
const double x = 2.f * u;
const double exp_x = expf(x); // good_approx_expf(x);
const double alpha = 1.f / (1.f + exp_x);
const double x = 2. * u;
const double exp_x = exp(x);
const double alpha = 1. / (1. + exp_x);
/* We want 2*(x*alpha - x*alpha^2 - exp(x)*alpha + 1) */
*W = 1.f - alpha;
*W = *W * x - exp_x;
*W = *W * alpha + 1.f;
*W *= 2.f;
#endif
/* We want 2*(x*alpha - x*alpha^2 - exp(x)*alpha + 1) */
*W = 1. - alpha;
*W = *W * x - exp_x;
*W = *W * alpha + 1.;
*W *= 2.;
#endif
#endif
}
......
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