gmx_bool pme_load_balance(pme_load_balancing_t pme_lb,
t_commrec *cr,
FILE *fp_err,
FILE *fp_log,
t_inputrec *ir,
t_state *state,
double cycles,
interaction_const_t *ic,
struct nonbonded_verlet_t *nbv,
struct gmx_pme_t ** pmedata,
gmx_int64_t step)
{
gmx_bool OK;
pme_setup_t *set;
double cycles_fast;
char buf[STRLEN], sbuf[22];
real rtab;
gmx_bool bUsesSimpleTables = TRUE;
if (pme_lb->stage == pme_lb->nstage)
{
return FALSE;
}
if (PAR(cr))
{
gmx_sumd(1, &cycles, cr);
cycles /= cr->nnodes;
}
set = &pme_lb->setup[pme_lb->cur];
set->count++;
rtab = ir->rlistlong + ir->tabext;
if (set->count % 2 == 1)
{
/* Skip the first cycle, because the first step after a switch
* is much slower due to allocation and/or caching effects.
*/
return TRUE;
}
sprintf(buf, "step %4s: ", gmx_step_str(step, sbuf));
print_grid(fp_err, fp_log, buf, "timed with", set, cycles);
if (set->count <= 2)
{
set->cycles = cycles;
}
else
{
if (cycles*PME_LB_ACCEL_TOL < set->cycles &&
pme_lb->stage == pme_lb->nstage - 1)
{
/* The performance went up a lot (due to e.g. DD load balancing).
* Add a stage, keep the minima, but rescan all setups.
*/
pme_lb->nstage++;
if (debug)
{
fprintf(debug, "The performance for grid %d %d %d went from %.3f to %.1f M-cycles, this is more than %f\n"
"Increased the number stages to %d"
" and ignoring the previous performance\n",
set->grid[XX], set->grid[YY], set->grid[ZZ],
cycles*1e-6, set->cycles*1e-6, PME_LB_ACCEL_TOL,
pme_lb->nstage);
}
}
set->cycles = min(set->cycles, cycles);
}
if (set->cycles < pme_lb->setup[pme_lb->fastest].cycles)
{
pme_lb->fastest = pme_lb->cur;
if (DOMAINDECOMP(cr))
{
/* We found a new fastest setting, ensure that with subsequent
* shorter cut-off's the dynamic load balancing does not make
* the use of the current cut-off impossible. This solution is
* a trade-off, as the PME load balancing and DD domain size
* load balancing can interact in complex ways.
* With the Verlet kernels, DD load imbalance will usually be
* mainly due to bonded interaction imbalance, which will often
* quickly push the domain boundaries beyond the limit for the
* optimal, PME load balanced, cut-off. But it could be that
* better overal performance can be obtained with a slightly
* shorter cut-off and better DD load balancing.
*/
change_dd_dlb_cutoff_limit(cr);
}
}
cycles_fast = pme_lb->setup[pme_lb->fastest].cycles;
/* Check in stage 0 if we should stop scanning grids.
* Stop when the time is more than SLOW_FAC longer than the fastest.
*/
if (pme_lb->stage == 0 && pme_lb->cur > 0 &&
cycles > pme_lb->setup[pme_lb->fastest].cycles*PME_LB_SLOW_FAC)
{
pme_lb->n = pme_lb->cur + 1;
/* Done with scanning, go to stage 1 */
switch_to_stage1(pme_lb);
}
if (pme_lb->stage == 0)
{
int gridsize_start;
gridsize_start = set->grid[XX]*set->grid[YY]*set->grid[ZZ];
do
{
if (pme_lb->cur+1 < pme_lb->n)
{
/* We had already generated the next setup */
OK = TRUE;
}
else
{
/* Find the next setup */
OK = pme_loadbal_increase_cutoff(pme_lb, ir->pme_order, cr->dd);
if (!OK)
{
pme_lb->elimited = epmelblimPMEGRID;
}
}
if (OK && ir->ePBC != epbcNONE)
{
OK = (sqr(pme_lb->setup[pme_lb->cur+1].rlistlong)
<= max_cutoff2(ir->ePBC, state->box));
if (!OK)
{
pme_lb->elimited = epmelblimBOX;
}
}
if (OK)
{
pme_lb->cur++;
if (DOMAINDECOMP(cr))
{
OK = change_dd_cutoff(cr, state, ir,
pme_lb->setup[pme_lb->cur].rlistlong);
if (!OK)
{
/* Failed: do not use this setup */
pme_lb->cur--;
pme_lb->elimited = epmelblimDD;
}
}
}
if (!OK)
{
/* We hit the upper limit for the cut-off,
* the setup should not go further than cur.
*/
pme_lb->n = pme_lb->cur + 1;
print_loadbal_limited(fp_err, fp_log, step, pme_lb);
/* Switch to the next stage */
switch_to_stage1(pme_lb);
}
}
while (OK &&
!(pme_lb->setup[pme_lb->cur].grid[XX]*
pme_lb->setup[pme_lb->cur].grid[YY]*
pme_lb->setup[pme_lb->cur].grid[ZZ] <
gridsize_start*PME_LB_GRID_SCALE_FAC
&&
pme_lb->setup[pme_lb->cur].grid_efficiency <
pme_lb->setup[pme_lb->cur-1].grid_efficiency*PME_LB_GRID_EFFICIENCY_REL_FAC));
}
if (pme_lb->stage > 0 && pme_lb->end == 1)
{
pme_lb->cur = 0;
pme_lb->stage = pme_lb->nstage;
}
else if (pme_lb->stage > 0 && pme_lb->end > 1)
{
/* If stage = nstage-1:
* scan over all setups, rerunning only those setups
* which are not much slower than the fastest
* else:
* use the next setup
*/
do
{
pme_lb->cur++;
if (pme_lb->cur == pme_lb->end)
{
pme_lb->stage++;
pme_lb->cur = pme_lb->start;
}
}
while (pme_lb->stage == pme_lb->nstage - 1 &&
pme_lb->setup[pme_lb->cur].count > 0 &&
pme_lb->setup[pme_lb->cur].cycles > cycles_fast*PME_LB_SLOW_FAC);
if (pme_lb->stage == pme_lb->nstage)
{
/* We are done optimizing, use the fastest setup we found */
pme_lb->cur = pme_lb->fastest;
}
}
if (DOMAINDECOMP(cr) && pme_lb->stage > 0)
{
OK = change_dd_cutoff(cr, state, ir, pme_lb->setup[pme_lb->cur].rlistlong);
if (!OK)
{
/* Failsafe solution */
if (pme_lb->cur > 1 && pme_lb->stage == pme_lb->nstage)
{
pme_lb->stage--;
}
pme_lb->fastest = 0;
pme_lb->start = 0;
pme_lb->end = pme_lb->cur;
pme_lb->cur = pme_lb->start;
pme_lb->elimited = epmelblimDD;
print_loadbal_limited(fp_err, fp_log, step, pme_lb);
}
}
/* Change the Coulomb cut-off and the PME grid */
set = &pme_lb->setup[pme_lb->cur];
ic->rcoulomb = set->rcut_coulomb;
ic->rlist = set->rlist;
ic->rlistlong = set->rlistlong;
ir->nstcalclr = set->nstcalclr;
ic->ewaldcoeff_q = set->ewaldcoeff_q;
/* TODO: centralize the code that sets the potentials shifts */
if (ic->coulomb_modifier == eintmodPOTSHIFT)
{
ic->sh_ewald = gmx_erfc(ic->ewaldcoeff_q*ic->rcoulomb);
}
if (EVDW_PME(ic->vdwtype))
{
/* We have PME for both Coulomb and VdW, set rvdw equal to rcoulomb */
ic->rvdw = set->rcut_coulomb;
ic->ewaldcoeff_lj = set->ewaldcoeff_lj;
if (ic->vdw_modifier == eintmodPOTSHIFT)
{
real crc2;
ic->dispersion_shift.cpot = -pow(ic->rvdw, -6.0);
ic->repulsion_shift.cpot = -pow(ic->rvdw, -12.0);
ic->sh_invrc6 = -ic->dispersion_shift.cpot;
crc2 = sqr(ic->ewaldcoeff_lj*ic->rvdw);
ic->sh_lj_ewald = (exp(-crc2)*(1 + crc2 + 0.5*crc2*crc2) - 1)*pow(ic->rvdw, -6.0);
}
}
bUsesSimpleTables = uses_simple_tables(ir->cutoff_scheme, nbv, 0);
nbnxn_gpu_pme_loadbal_update_param(nbv, ic);
/* With tMPI + GPUs some ranks may be sharing GPU(s) and therefore
* also sharing texture references. To keep the code simple, we don't
* treat texture references as shared resources, but this means that
* the coulomb_tab texture ref will get updated by multiple threads.
* Hence, to ensure that the non-bonded kernels don't start before all
* texture binding operations are finished, we need to wait for all ranks
* to arrive here before continuing.
*
* Note that we could omit this barrier if GPUs are not shared (or
* texture objects are used), but as this is initialization code, there
* is not point in complicating things.
*/
#ifdef GMX_THREAD_MPI
if (PAR(cr) && use_GPU(nbv))
{
gmx_barrier(cr);
}
#endif /* GMX_THREAD_MPI */
/* Usually we won't need the simple tables with GPUs.
* But we do with hybrid acceleration and with free energy.
* To avoid bugs, we always re-initialize the simple tables here.
*/
init_interaction_const_tables(NULL, ic, bUsesSimpleTables, rtab);
if (cr->duty & DUTY_PME)
{
if (pme_lb->setup[pme_lb->cur].pmedata == NULL)
{
/* Generate a new PME data structure,
* copying part of the old pointers.
*/
gmx_pme_reinit(&set->pmedata,
cr, pme_lb->setup[0].pmedata, ir,
set->grid);
}
*pmedata = set->pmedata;
}
else
{
/* Tell our PME-only node to switch grid */
gmx_pme_send_switchgrid(cr, set->grid, set->ewaldcoeff_q, set->ewaldcoeff_lj);
}
if (debug)
{
print_grid(NULL, debug, "", "switched to", set, -1);
}
if (pme_lb->stage == pme_lb->nstage)
{
print_grid(fp_err, fp_log, "", "optimal", set, -1);
}
return TRUE;
}
gmx_bool pme_load_balance(pme_load_balancing_t pme_lb,
t_commrec *cr,
FILE *fp_err,
FILE *fp_log,
t_inputrec *ir,
t_state *state,
double cycles,
interaction_const_t *ic,
nonbonded_verlet_t *nbv,
gmx_pme_t *pmedata,
gmx_large_int_t step)
{
gmx_bool OK;
pme_setup_t *set;
double cycles_fast;
char buf[STRLEN], sbuf[22];
real rtab;
gmx_bool bUsesSimpleTables = TRUE;
if (pme_lb->stage == pme_lb->nstage)
{
return FALSE;
}
if (PAR(cr))
{
gmx_sumd(1, &cycles, cr);
cycles /= cr->nnodes;
}
set = &pme_lb->setup[pme_lb->cur];
set->count++;
rtab = ir->rlistlong + ir->tabext;
if (set->count % 2 == 1)
{
/* Skip the first cycle, because the first step after a switch
* is much slower due to allocation and/or caching effects.
*/
return TRUE;
}
sprintf(buf, "step %4s: ", gmx_step_str(step, sbuf));
print_grid(fp_err, fp_log, buf, "timed with", set, cycles);
if (set->count <= 2)
{
set->cycles = cycles;
}
else
{
if (cycles*PME_LB_ACCEL_TOL < set->cycles &&
pme_lb->stage == pme_lb->nstage - 1)
{
/* The performance went up a lot (due to e.g. DD load balancing).
* Add a stage, keep the minima, but rescan all setups.
*/
pme_lb->nstage++;
if (debug)
{
fprintf(debug, "The performance for grid %d %d %d went from %.3f to %.1f M-cycles, this is more than %f\n"
"Increased the number stages to %d"
" and ignoring the previous performance\n",
set->grid[XX], set->grid[YY], set->grid[ZZ],
cycles*1e-6, set->cycles*1e-6, PME_LB_ACCEL_TOL,
pme_lb->nstage);
}
}
set->cycles = min(set->cycles, cycles);
}
if (set->cycles < pme_lb->setup[pme_lb->fastest].cycles)
{
pme_lb->fastest = pme_lb->cur;
if (DOMAINDECOMP(cr))
{
/* We found a new fastest setting, ensure that with subsequent
* shorter cut-off's the dynamic load balancing does not make
* the use of the current cut-off impossible. This solution is
* a trade-off, as the PME load balancing and DD domain size
* load balancing can interact in complex ways.
* With the Verlet kernels, DD load imbalance will usually be
* mainly due to bonded interaction imbalance, which will often
* quickly push the domain boundaries beyond the limit for the
* optimal, PME load balanced, cut-off. But it could be that
* better overal performance can be obtained with a slightly
* shorter cut-off and better DD load balancing.
*/
change_dd_dlb_cutoff_limit(cr);
}
}
cycles_fast = pme_lb->setup[pme_lb->fastest].cycles;
/* Check in stage 0 if we should stop scanning grids.
* Stop when the time is more than SLOW_FAC longer than the fastest.
*/
if (pme_lb->stage == 0 && pme_lb->cur > 0 &&
cycles > pme_lb->setup[pme_lb->fastest].cycles*PME_LB_SLOW_FAC)
{
pme_lb->n = pme_lb->cur + 1;
/* Done with scanning, go to stage 1 */
switch_to_stage1(pme_lb);
}
if (pme_lb->stage == 0)
{
int gridsize_start;
gridsize_start = set->grid[XX]*set->grid[YY]*set->grid[ZZ];
do
{
if (pme_lb->cur+1 < pme_lb->n)
{
/* We had already generated the next setup */
OK = TRUE;
}
else
{
/* Find the next setup */
OK = pme_loadbal_increase_cutoff(pme_lb, ir->pme_order);
}
if (OK && ir->ePBC != epbcNONE)
{
OK = (sqr(pme_lb->setup[pme_lb->cur+1].rlistlong)
<= max_cutoff2(ir->ePBC, state->box));
if (!OK)
{
pme_lb->elimited = epmelblimBOX;
}
}
if (OK)
{
pme_lb->cur++;
if (DOMAINDECOMP(cr))
{
OK = change_dd_cutoff(cr, state, ir,
pme_lb->setup[pme_lb->cur].rlistlong);
if (!OK)
{
/* Failed: do not use this setup */
pme_lb->cur--;
pme_lb->elimited = epmelblimDD;
}
}
}
if (!OK)
{
/* We hit the upper limit for the cut-off,
* the setup should not go further than cur.
*/
pme_lb->n = pme_lb->cur + 1;
print_loadbal_limited(fp_err, fp_log, step, pme_lb);
/* Switch to the next stage */
switch_to_stage1(pme_lb);
}
}
while (OK &&
!(pme_lb->setup[pme_lb->cur].grid[XX]*
pme_lb->setup[pme_lb->cur].grid[YY]*
pme_lb->setup[pme_lb->cur].grid[ZZ] <
gridsize_start*PME_LB_GRID_SCALE_FAC
&&
pme_lb->setup[pme_lb->cur].grid_efficiency <
pme_lb->setup[pme_lb->cur-1].grid_efficiency*PME_LB_GRID_EFFICIENCY_REL_FAC));
}
if (pme_lb->stage > 0 && pme_lb->end == 1)
{
pme_lb->cur = 0;
pme_lb->stage = pme_lb->nstage;
}
else if (pme_lb->stage > 0 && pme_lb->end > 1)
{
/* If stage = nstage-1:
* scan over all setups, rerunning only those setups
* which are not much slower than the fastest
* else:
* use the next setup
*/
do
{
pme_lb->cur++;
if (pme_lb->cur == pme_lb->end)
{
pme_lb->stage++;
pme_lb->cur = pme_lb->start;
}
}
while (pme_lb->stage == pme_lb->nstage - 1 &&
pme_lb->setup[pme_lb->cur].count > 0 &&
pme_lb->setup[pme_lb->cur].cycles > cycles_fast*PME_LB_SLOW_FAC);
if (pme_lb->stage == pme_lb->nstage)
{
/* We are done optimizing, use the fastest setup we found */
pme_lb->cur = pme_lb->fastest;
}
}
if (DOMAINDECOMP(cr) && pme_lb->stage > 0)
{
OK = change_dd_cutoff(cr, state, ir, pme_lb->setup[pme_lb->cur].rlistlong);
if (!OK)
{
/* Failsafe solution */
if (pme_lb->cur > 1 && pme_lb->stage == pme_lb->nstage)
{
pme_lb->stage--;
}
pme_lb->fastest = 0;
pme_lb->start = 0;
pme_lb->end = pme_lb->cur;
pme_lb->cur = pme_lb->start;
pme_lb->elimited = epmelblimDD;
print_loadbal_limited(fp_err, fp_log, step, pme_lb);
}
}
/* Change the Coulomb cut-off and the PME grid */
set = &pme_lb->setup[pme_lb->cur];
ic->rcoulomb = set->rcut_coulomb;
ic->rlist = set->rlist;
ic->rlistlong = set->rlistlong;
ir->nstcalclr = set->nstcalclr;
ic->ewaldcoeff = set->ewaldcoeff;
bUsesSimpleTables = uses_simple_tables(ir->cutoff_scheme, nbv, 0);
if (pme_lb->cutoff_scheme == ecutsVERLET &&
nbv->grp[0].kernel_type == nbnxnk8x8x8_CUDA)
{
nbnxn_cuda_pme_loadbal_update_param(nbv->cu_nbv, ic);
}
else
{
init_interaction_const_tables(NULL, ic, bUsesSimpleTables,
rtab);
}
if (pme_lb->cutoff_scheme == ecutsVERLET && nbv->ngrp > 1)
{
init_interaction_const_tables(NULL, ic, bUsesSimpleTables,
rtab);
}
if (cr->duty & DUTY_PME)
{
if (pme_lb->setup[pme_lb->cur].pmedata == NULL)
{
/* Generate a new PME data structure,
* copying part of the old pointers.
*/
gmx_pme_reinit(&set->pmedata,
cr, pme_lb->setup[0].pmedata, ir,
set->grid);
}
*pmedata = set->pmedata;
}
else
{
/* Tell our PME-only node to switch grid */
gmx_pme_send_switchgrid(cr, set->grid, set->ewaldcoeff);
}
if (debug)
{
print_grid(NULL, debug, "", "switched to", set, -1);
}
if (pme_lb->stage == pme_lb->nstage)
{
print_grid(fp_err, fp_log, "", "optimal", set, -1);
}
return TRUE;
}