Skip to content
GitLab
Commit 9dbbde7a authored by Loic Hausammann's avatar Loic Hausammann
Browse files

implement the stars density over mpi

parent aa863097
Hide whitespace changes
Inline Side-by-side
examples/main.c
View file @ 9dbbde7a
......@@ -456,7 +456,6 @@ int main(int argc, char *argv[]) {
#ifdef WITH_MPI
if (with_mpole_reconstruction && nr_nodes > 1)
error("Cannot reconstruct m-poles every step over MPI (yet).");
if (with_feedback) error("Can't run with feedback over MPI (yet).");
if (with_star_formation)
error("Can't run with star formation over MPI (yet)");
if (with_limiter) error("Can't run with time-step limiter over MPI (yet)");
......
src/cell.c
View file @ 9dbbde7a
......@@ -181,6 +181,7 @@ int cell_pack(struct cell *restrict c, struct pcell *restrict pc,
/* Start by packing the data of the current cell. */
pc->hydro.h_max = c->hydro.h_max;
pc->stars.h_max = c->stars.h_max;
pc->hydro.ti_end_min = c->hydro.ti_end_min;
pc->hydro.ti_end_max = c->hydro.ti_end_max;
pc->grav.ti_end_min = c->grav.ti_end_min;
......@@ -285,6 +286,7 @@ int cell_unpack(struct pcell *restrict pc, struct cell *restrict c,
/* Unpack the current pcell. */
c->hydro.h_max = pc->hydro.h_max;
c->stars.h_max = pc->stars.h_max;
c->hydro.ti_end_min = pc->hydro.ti_end_min;
c->hydro.ti_end_max = pc->hydro.ti_end_max;
c->grav.ti_end_min = pc->grav.ti_end_min;
......@@ -1838,6 +1840,9 @@ void cell_activate_stars_sorts_up(struct cell *c, struct scheduler *s) {
*/
void cell_activate_stars_sorts(struct cell *c, int sid, struct scheduler *s) {
// TODO Alexei, remove this
if (c->nodeID != engine_rank) return;
/* Do we need to re-sort? */
if (c->stars.dx_max_sort > space_maxreldx * c->dmin) {
......@@ -3144,6 +3149,10 @@ int cell_unskip_stars_tasks(struct cell *c, struct scheduler *s) {
struct cell *cj = t->cj;
const int ci_active = cell_is_active_stars(ci, e);
const int cj_active = (cj != NULL) ? cell_is_active_stars(cj, e) : 0;
#ifdef WITH_MPI
const int ci_nodeID = ci->nodeID;
const int cj_nodeID = (cj != NULL) ? cj->nodeID : -1;
#endif
/* Only activate tasks that involve a local active cell. */
if ((ci_active && ci->nodeID == nodeID) ||
......@@ -3161,38 +3170,42 @@ int cell_unskip_stars_tasks(struct cell *c, struct scheduler *s) {
/* Set the correct sorting flags and activate hydro drifts */
else if (t->type == task_type_pair) {
/* Do ci */
/* stars for ci */
atomic_or(&ci->stars.requires_sorts, 1 << t->flags);
ci->stars.dx_max_sort_old = ci->stars.dx_max_sort;
/* hydro for cj */
atomic_or(&cj->hydro.requires_sorts, 1 << t->flags);
cj->hydro.dx_max_sort_old = cj->hydro.dx_max_sort;
/* Activate the drift tasks. */
if (ci->nodeID == nodeID) cell_activate_drift_spart(ci, s);
if (cj->nodeID == nodeID) cell_activate_drift_part(cj, s);
/* Check the sorts and activate them if needed. */
cell_activate_stars_sorts(ci, t->flags, s);
cell_activate_hydro_sorts(cj, t->flags, s);
if (ci_active && cj->hydro.count != 0 && ci->stars.count != 0) {
/* stars for ci */
atomic_or(&ci->stars.requires_sorts, 1 << t->flags);
ci->stars.dx_max_sort_old = ci->stars.dx_max_sort;
/* hydro for cj */
atomic_or(&cj->hydro.requires_sorts, 1 << t->flags);
cj->hydro.dx_max_sort_old = cj->hydro.dx_max_sort;
/* Activate the drift tasks. */
if (ci->nodeID == nodeID) cell_activate_drift_spart(ci, s);
if (cj->nodeID == nodeID) cell_activate_drift_part(cj, s);
/* Check the sorts and activate them if needed. */
cell_activate_stars_sorts(ci, t->flags, s);
cell_activate_hydro_sorts(cj, t->flags, s);
}
/* Do cj */
/* hydro for ci */
atomic_or(&ci->hydro.requires_sorts, 1 << t->flags);
ci->hydro.dx_max_sort_old = ci->hydro.dx_max_sort;
/* stars for cj */
atomic_or(&cj->stars.requires_sorts, 1 << t->flags);
cj->stars.dx_max_sort_old = cj->stars.dx_max_sort;
/* Activate the drift tasks. */
if (cj->nodeID == nodeID) cell_activate_drift_spart(cj, s);
if (ci->nodeID == nodeID) cell_activate_drift_part(ci, s);
/* Check the sorts and activate them if needed. */
cell_activate_hydro_sorts(ci, t->flags, s);
cell_activate_stars_sorts(cj, t->flags, s);
if (cj_active && ci->hydro.count != 0 && cj->stars.count != 0) {
/* hydro for ci */
atomic_or(&ci->hydro.requires_sorts, 1 << t->flags);
ci->hydro.dx_max_sort_old = ci->hydro.dx_max_sort;
/* stars for cj */
atomic_or(&cj->stars.requires_sorts, 1 << t->flags);
cj->stars.dx_max_sort_old = cj->stars.dx_max_sort;
/* Activate the drift tasks. */
if (cj->nodeID == nodeID) cell_activate_drift_spart(cj, s);
if (ci->nodeID == nodeID) cell_activate_drift_part(ci, s);
/* Check the sorts and activate them if needed. */
cell_activate_hydro_sorts(ci, t->flags, s);
cell_activate_stars_sorts(cj, t->flags, s);
}
}
/* Store current values of dx_max and h_max. */
......@@ -3207,85 +3220,81 @@ int cell_unskip_stars_tasks(struct cell *c, struct scheduler *s) {
/* Check whether there was too much particle motion, i.e. the
cell neighbour conditions were violated. */
if (cell_need_rebuild_for_stars_pair(ci, cj)) rebuild = 1;
if (cell_need_rebuild_for_hydro_pair(ci, cj)) rebuild = 1;
#ifdef WITH_MPI
error("MPI with stars not implemented");
/* /\* Activate the send/recv tasks. *\/ */
/* if (ci->nodeID != nodeID) { */
/* /\* If the local cell is active, receive data from the foreign cell.
* *\/ */
/* if (cj_active) { */
/* scheduler_activate(s, ci->hydro.recv_xv); */
/* if (ci_active) { */
/* scheduler_activate(s, ci->hydro.recv_rho); */
/* } */
/* } */
/* Activate the send/recv tasks. */
if (ci_nodeID != nodeID) {
/* /\* If the foreign cell is active, we want its ti_end values. *\/ */
/* if (ci_active) scheduler_activate(s, ci->mpi.recv_ti); */
// TODO Alexei: In this section, you will find some comments that
// are from the hydro code. It should look the same for the feedback.
/* If the local cell is active, receive data from the foreign cell. */
if (cj_active) {
scheduler_activate(s, ci->mpi.hydro.recv_xv);
/* if (ci_active) { */
/* scheduler_activate(s, ci->mpi.hydro.recv_rho); */
/* } */
}
/* /\* Is the foreign cell active and will need stuff from us? *\/ */
/* if (ci_active) { */
/* /\* If the foreign cell is active, we want its ti_end values. *\/ */
/* if (ci_active) scheduler_activate(s, ci->mpi.recv_ti); */
/* scheduler_activate_send(s, cj->hydro.send_xv, ci->nodeID); */
/* Is the foreign cell active and will need stuff from us? */
if (ci_active) {
/* /\* Drift the cell which will be sent; note that not all sent */
/* particles will be drifted, only those that are needed. *\/ */
/* cell_activate_drift_part(cj, s); */
scheduler_activate_send(s, cj->mpi.hydro.send_xv, ci_nodeID);
/* /\* If the local cell is also active, more stuff will be needed.
* *\/ */
/* if (cj_active) { */
/* scheduler_activate_send(s, cj->hydro.send_rho, ci->nodeID); */
/* Drift the cell which will be sent; note that not all sent
particles will be drifted, only those that are needed. */
cell_activate_drift_part(cj, s);
/* } */
/* } */
/* /\* If the local cell is also active, more stuff will be needed.
* *\/ */
/* if (cj_active) { */
/* scheduler_activate_send(s, cj->mpi.hydro.send_rho, ci_nodeID); */
/* /\* If the local cell is active, send its ti_end values. *\/ */
/* if (cj_active) scheduler_activate_send(s, cj->mpi.send_ti,
* ci->nodeID);
*/
/* } */
}
/* } else if (cj->nodeID != nodeID) { */
/* /\* If the local cell is active, send its ti_end values. *\/ */
/* if (cj_active) scheduler_activate_send(s, cj->mpi.send_ti,
* ci_nodeID); */
/* /\* If the local cell is active, receive data from the foreign cell.
* *\/ */
/* if (ci_active) { */
/* scheduler_activate(s, cj->hydro.recv_xv); */
/* if (cj_active) { */
/* scheduler_activate(s, cj->hydro.recv_rho); */
} else if (cj_nodeID != nodeID) {
/* } */
/* } */
/* If the local cell is active, receive data from the foreign cell. */
if (ci_active) {
scheduler_activate(s, cj->mpi.hydro.recv_xv);
/* if (cj_active) { */
/* scheduler_activate(s, cj->mpi.hydro.recv_rho); */
/* } */
}
/* /\* If the foreign cell is active, we want its ti_end values. *\/ */
/* if (cj_active) scheduler_activate(s, cj->mpi.recv_ti); */
/* /\* If the foreign cell is active, we want its ti_end values. *\/ */
/* if (cj_active) scheduler_activate(s, cj->mpi.recv_ti); */
/* /\* Is the foreign cell active and will need stuff from us? *\/ */
/* if (cj_active) { */
/* Is the foreign cell active and will need stuff from us? */
if (cj_active) {
/* scheduler_activate_send(s, ci->hydro.send_xv, cj->nodeID); */
scheduler_activate_send(s, ci->mpi.hydro.send_xv, cj_nodeID);
/* /\* Drift the cell which will be sent; note that not all sent */
/* particles will be drifted, only those that are needed. *\/ */
/* cell_activate_drift_part(ci, s); */
/* Drift the cell which will be sent; note that not all sent
particles will be drifted, only those that are needed. */
cell_activate_drift_part(ci, s);
/* /\* If the local cell is also active, more stuff will be needed.
* *\/ */
/* if (ci_active) { */
/* /\* If the local cell is also active, more stuff will be needed.
* *\/ */
/* if (ci_active) { */
/* scheduler_activate_send(s, ci->hydro.send_rho, cj->nodeID); */
/* scheduler_activate_send(s, ci->mpi.hydro.send_rho, cj_nodeID); */
/* } */
/* } */
/* } */
}
/* /\* If the local cell is active, send its ti_end values. *\/ */
/* if (ci_active) scheduler_activate_send(s, ci->mpi.send_ti,
* cj->nodeID);
*/
/* } */
/* /\* If the local cell is active, send its ti_end values. *\/ */
/* if (ci_active) scheduler_activate_send(s, ci->mpi.send_ti,
* cj_nodeID); */
}
#endif
}
}
......
src/cell.h
View file @ 9dbbde7a
......@@ -992,6 +992,23 @@ cell_need_rebuild_for_hydro_pair(const struct cell *ci, const struct cell *cj) {
ci->hydro.dx_max_part + cj->hydro.dx_max_part >
cj->dmin);
}
/**
* @brief Have particles in a pair of cells moved too much and require a rebuild
* ?
*
* @param ci The first #cell.
* @param cj The second #cell.
*/
__attribute__((always_inline)) INLINE static int
cell_need_rebuild_for_stars_pair(const struct cell *ci, const struct cell *cj) {
/* Is the cut-off radius plus the max distance the parts in both cells have */
/* moved larger than the cell size ? */
/* Note ci->dmin == cj->dmin */
return (kernel_gamma * max(ci->stars.h_max, cj->stars.h_max) +
ci->stars.dx_max_part + cj->stars.dx_max_part >
cj->dmin);
}
/**
* @brief Have star particles in a pair of cells moved too much and require a
......
src/debug.c
View file @ 9dbbde7a
......@@ -179,6 +179,14 @@ int checkSpacehmax(struct space *s) {
}
}
float cell_stars_h_max = 0.0f;
for (int k = 0; k < s->nr_cells; k++) {
if (s->cells_top[k].nodeID == s->e->nodeID &&
s->cells_top[k].stars.h_max > cell_stars_h_max) {
cell_stars_h_max = s->cells_top[k].stars.h_max;
}
}
/* Now all particles. */
float part_h_max = 0.0f;
for (size_t k = 0; k < s->nr_parts; k++) {
......@@ -187,10 +195,21 @@ int checkSpacehmax(struct space *s) {
}
}
/* Now all the sparticles. */
float spart_h_max = 0.0f;
for (size_t k = 0; k < s->nr_sparts; k++) {
if (s->sparts[k].h > spart_h_max) {
spart_h_max = s->sparts[k].h;
}
}
/* If within some epsilon we are OK. */
if (fabsf(cell_h_max - part_h_max) <= FLT_EPSILON) return 1;
if (fabsf(cell_h_max - part_h_max) <= FLT_EPSILON &&
fabsf(cell_stars_h_max - spart_h_max) <= FLT_EPSILON)
return 1;
/* There is a problem. Hunt it down. */
/* part */
for (int k = 0; k < s->nr_cells; k++) {
if (s->cells_top[k].nodeID == s->e->nodeID) {
if (s->cells_top[k].hydro.h_max > part_h_max) {
......@@ -207,6 +226,23 @@ int checkSpacehmax(struct space *s) {
}
}
/* spart */
for (int k = 0; k < s->nr_cells; k++) {
if (s->cells_top[k].nodeID == s->e->nodeID) {
if (s->cells_top[k].stars.h_max > spart_h_max) {
message("cell %d is inconsistent (%f > %f)", k,
s->cells_top[k].stars.h_max, spart_h_max);
}
}
}
for (size_t k = 0; k < s->nr_sparts; k++) {
if (s->sparts[k].h > cell_stars_h_max) {
message("spart %lld is inconsistent (%f > %f)", s->sparts[k].id,
s->sparts[k].h, cell_stars_h_max);
}
}
return 0;
}
......@@ -225,6 +261,8 @@ int checkCellhdxmax(const struct cell *c, int *depth) {
float h_max = 0.0f;
float dx_max = 0.0f;
float stars_h_max = 0.0f;
float stars_dx_max = 0.0f;
int result = 1;
const double loc_min[3] = {c->loc[0], c->loc[1], c->loc[2]};
......@@ -260,6 +298,33 @@ int checkCellhdxmax(const struct cell *c, int *depth) {
dx_max = max(dx_max, sqrt(dx2));
}
const size_t nr_sparts = c->stars.count;
struct spart *sparts = c->stars.parts;
for (size_t k = 0; k < nr_sparts; k++) {
struct spart *const sp = &sparts[k];
if (sp->x[0] < loc_min[0] || sp->x[0] >= loc_max[0] ||
sp->x[1] < loc_min[1] || sp->x[1] >= loc_max[1] ||
sp->x[2] < loc_min[2] || sp->x[2] >= loc_max[2]) {
message(
"Inconsistent part position p->x=[%e %e %e], c->loc=[%e %e %e] "
"c->width=[%e %e %e]",
sp->x[0], sp->x[1], sp->x[2], c->loc[0], c->loc[1], c->loc[2],
c->width[0], c->width[1], c->width[2]);
result = 0;
}
const float dx2 = sp->x_diff[0] * sp->x_diff[0] +
sp->x_diff[1] * sp->x_diff[1] +
sp->x_diff[2] * sp->x_diff[2];
stars_h_max = max(stars_h_max, sp->h);
stars_dx_max = max(stars_dx_max, sqrt(dx2));
}
if (c->split) {
for (int k = 0; k < 8; k++) {
if (c->progeny[k] != NULL) {
......@@ -283,6 +348,19 @@ int checkCellhdxmax(const struct cell *c, int *depth) {
result = 0;
}
if (c->stars.h_max != stars_h_max) {
message("%d Inconsistent stars_h_max: cell %f != parts %f", *depth,
c->stars.h_max, stars_h_max);
message("location: %f %f %f", c->loc[0], c->loc[1], c->loc[2]);
result = 0;
}
if (c->stars.dx_max_part != stars_dx_max) {
message("%d Inconsistent stars_dx_max: %f != %f", *depth,
c->stars.dx_max_part, stars_dx_max);
message("location: %f %f %f", c->loc[0], c->loc[1], c->loc[2]);
result = 0;
}
return result;
}
......
src/engine_maketasks.c
View file @ 9dbbde7a
......@@ -203,6 +203,86 @@ void engine_addtasks_send_hydro(struct engine *e, struct cell *ci,
#endif
}
/**
* @brief Add send tasks for the stars pairs to a hierarchy of cells.
*
* @param e The #engine.
* @param ci The sending #cell.
* @param cj Dummy cell containing the nodeID of the receiving node.
* @param t_xv The send_xv #task, if it has already been created.
* @param t_rho The send_rho #task, if it has already been created.
*/
void engine_addtasks_send_stars(struct engine *e, struct cell *ci,
struct cell *cj, struct task *t_xv,
struct task *t_rho) {
#ifdef WITH_MPI
struct link *l = NULL;
struct scheduler *s = &e->sched;
const int nodeID = cj->nodeID;
/* Check if any of the density tasks are for the target node. */
for (l = ci->stars.density; l != NULL; l = l->next)
if (l->t->ci->nodeID == nodeID ||
(l->t->cj != NULL && l->t->cj->nodeID == nodeID))
break;
/* If so, attach send tasks. */
if (l != NULL) {
/* Get the task if created in hydro part */
struct link *hydro = NULL;
for (hydro = ci->mpi.hydro.send_xv; hydro != NULL; hydro = hydro->next) {
if (hydro->t->ci->nodeID == nodeID ||
(hydro->t->cj != NULL && hydro->t->cj->nodeID == nodeID)) {
break;
}
}
// TODO Alexei: I guess that you can assume that if the send_xv exists,
// send_rho exists too
if (t_xv == NULL) {
/* Already exists, just need to get it */
if (hydro != NULL) {
// TODO Alexei: set t_feedback
t_xv = hydro->t;
/* This task does not exists, need to create it */
} else {
// TODO Alexei: create task and do correct unlocks
/* Make sure this cell is tagged. */
cell_ensure_tagged(ci);
/* Create the tasks and their dependencies? */
t_xv = scheduler_addtask(s, task_type_send, task_subtype_xv,
ci->mpi.tag, 0, ci, cj);
/* Drift before you send */
scheduler_addunlock(s, ci->hydro.super->hydro.drift, t_xv);
}
}
if (hydro == NULL) {
engine_addlink(e, &ci->mpi.hydro.send_xv, t_xv);
// TODO Alexei: addlink
/* engine_addlink(e, &ci->mpi.hydro.send_rho, t_rho); */
}
}
/* Recurse? */
if (ci->split)
for (int k = 0; k < 8; k++)
if (ci->progeny[k] != NULL)
engine_addtasks_send_stars(e, ci->progeny[k], cj, t_xv, t_rho);
#else
error("SWIFT was not compiled with MPI support.");
#endif
}
/**
* @brief Add send tasks for the time-step to a hierarchy of cells.
*
......@@ -348,6 +428,74 @@ void engine_addtasks_recv_hydro(struct engine *e, struct cell *c,
#endif
}
/**
* @brief Add recv tasks for stars pairs to a hierarchy of cells.
*
* @param e The #engine.
* @param c The foreign #cell.
* @param t_xv The recv_xv #task, if it has already been created.
* @param t_rho The recv_rho #task, if it has already been created.
*/
void engine_addtasks_recv_stars(struct engine *e, struct cell *c,
struct task *t_xv, struct task *t_rho) {
#ifdef WITH_MPI
struct scheduler *s = &e->sched;
int new_task = 0;
/* Have we reached a level where there are any stars (or hydro) tasks ? */
if (t_xv == NULL && (c->stars.density != NULL || c->hydro.density != NULL)) {
#ifdef SWIFT_DEBUG_CHECKS
/* Make sure this cell has a valid tag. */
if (c->mpi.tag < 0) error("Trying to receive from untagged cell.");
#endif // SWIFT_DEBUG_CHECKS
/* Create the tasks. */
if (c->mpi.hydro.recv_xv == NULL) {
new_task = 1;
t_xv = scheduler_addtask(s, task_type_recv, task_subtype_xv, c->mpi.tag,
0, c, NULL);
// TODO Alexei: create t_feedback task
/* t_rho = scheduler_addtask(s, task_type_recv, task_subtype_rho,
* c->mpi.tag, */
/* 0, c, NULL); */
} else {
// TODO Alexei: set t_feedback
t_xv = c->mpi.hydro.recv_xv;
}
}
// TODO Alexei: set pointer
c->mpi.hydro.recv_xv = t_xv;
/* c->mpi.hydro.recv_rho = t_rho; */
/* Add dependencies. */
if (c->hydro.sorts != NULL && new_task) {
scheduler_addunlock(s, t_xv, c->hydro.sorts);
}
// TODO Alexei: You will need to sort the particles after receiving the spart
for (struct link *l = c->stars.density; l != NULL; l = l->next) {
scheduler_addunlock(s, t_xv, l->t);
// TODO Alexei: I guess that you will need to unlock the recv here
/* scheduler_addunlock(s, l->t, t_rho); */
}
// TODO Alexei: unlock feedback task
/* for (struct link *l = c->hydro.force; l != NULL; l = l->next) */
/* scheduler_addunlock(s, t_rho, l->t); */
/* Recurse? */
if (c->split)
for (int k = 0; k < 8; k++)
if (c->progeny[k] != NULL)
engine_addtasks_recv_stars(e, c->progeny[k], t_xv, t_rho);
#else
error("SWIFT was not compiled with MPI support.");
#endif
}
/**
* @brief Add recv tasks for gravity pairs to a hierarchy of cells.
*
......@@ -784,12 +932,12 @@ void engine_make_hierarchical_tasks_stars(struct engine *e, struct cell *c) {
/* Are we in a super-cell ? */
if (c->super == c) {
/* Add the sort task. */
c->stars.sorts = scheduler_addtask(s, task_type_stars_sort,
task_subtype_none, 0, 0, c, NULL);
/* Local tasks only... */
if (c->nodeID == e->nodeID) {
// TODO Alexei: do not need to be only on local node with feedback
/* Add the sort task. */
c->stars.sorts = scheduler_addtask(s, task_type_stars_sort,
task_subtype_none, 0, 0, c, NULL);
/* Generate the ghost tasks. */
c->stars.ghost_in =
......@@ -1818,6 +1966,9 @@ void engine_make_extra_starsloop_tasks_mapper(void *map_data, int num_elements,
else if (t->type == task_type_self &&
t->subtype == task_subtype_stars_density) {
/* Make the self-density tasks depend on the drifts. */
scheduler_addunlock(sched, t->ci->hydro.super->hydro.drift, t);
/* Make the self-density tasks depend on the drift and gravity drift. */
scheduler_addunlock(sched, t->ci->hydro.super->hydro.drift, t);
scheduler_addunlock(sched, t->ci->super->grav.drift, t);
......@@ -1844,19 +1995,28 @@ void engine_make_extra_starsloop_tasks_mapper(void *map_data, int num_elements,
/* Make all stars density tasks depend on the hydro drift and sorts,
* gravity drift and star sorts. */
if (t->ci->nodeID == engine_rank)
scheduler_addunlock(sched, t->ci->super->hydro.drift, t);
scheduler_addunlock(sched, t->ci->super->hydro.sorts, t);
if (t->cj->nodeID == engine_rank)
scheduler_addunlock(sched, t->cj->super->grav.drift, t);
scheduler_addunlock(sched, t->ci->super->stars.sorts, t);
scheduler_addunlock(sched, t->ci->hydro.super->hydro.drift, t);
scheduler_addunlock(sched, t->ci->hydro.super->hydro.sorts, t);
if (t->ci->super != t->cj->super) {
if (t->ci->nodeID == engine_rank) {
scheduler_addunlock(sched, t->ci->super->grav.drift, t);
// TODO Alexei: the stars in foreign cells need to be sorted before
// the feedback loop and after the ghosts
scheduler_addunlock(sched, t->ci->super->stars.sorts, t);
}
if (t->ci->hydro.super != t->cj->hydro.super) {
if (t->cj->nodeID == engine_rank)
scheduler_addunlock(sched, t->cj->super->hydro.drift, t);