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38 * \brief This file contains function definitions necessary for
39 * managing automatic load balance of PME calculations (Coulomb and
42 * \author Berk Hess <hess@kth.se>
43 * \ingroup module_ewald
47 #include "pme_load_balancing.h"
54 #include "gromacs/domdec/dlb.h"
55 #include "gromacs/domdec/domdec.h"
56 #include "gromacs/domdec/domdec_network.h"
57 #include "gromacs/domdec/domdec_struct.h"
58 #include "gromacs/domdec/partition.h"
59 #include "gromacs/ewald/ewald_utils.h"
60 #include "gromacs/ewald/pme.h"
61 #include "gromacs/fft/calcgrid.h"
62 #include "gromacs/gmxlib/network.h"
63 #include "gromacs/math/functions.h"
64 #include "gromacs/math/vec.h"
65 #include "gromacs/mdlib/dispersioncorrection.h"
66 #include "gromacs/mdlib/forcerec.h"
67 #include "gromacs/mdtypes/commrec.h"
68 #include "gromacs/mdtypes/inputrec.h"
69 #include "gromacs/mdtypes/md_enums.h"
70 #include "gromacs/mdtypes/state.h"
71 #include "gromacs/nbnxm/gpu_data_mgmt.h"
72 #include "gromacs/nbnxm/nbnxm.h"
73 #include "gromacs/pbcutil/pbc.h"
74 #include "gromacs/timing/wallcycle.h"
75 #include "gromacs/utility/cstringutil.h"
76 #include "gromacs/utility/fatalerror.h"
77 #include "gromacs/utility/gmxassert.h"
78 #include "gromacs/utility/logger.h"
79 #include "gromacs/utility/smalloc.h"
80 #include "gromacs/utility/strconvert.h"
82 #include "pme_internal.h"
84 /*! \brief Parameters and settings for one PP-PME setup */
87 real rcut_coulomb; /**< Coulomb cut-off */
88 real rlistOuter; /**< cut-off for the outer pair-list */
89 real rlistInner; /**< cut-off for the inner pair-list */
90 real spacing; /**< (largest) PME grid spacing */
91 ivec grid; /**< the PME grid dimensions */
92 real grid_efficiency; /**< ineffiency factor for non-uniform grids <= 1 */
93 real ewaldcoeff_q; /**< Electrostatic Ewald coefficient */
94 real ewaldcoeff_lj; /**< LJ Ewald coefficient, only for the call to send_switchgrid */
95 struct gmx_pme_t* pmedata; /**< the data structure used in the PME code */
96 int count; /**< number of times this setup has been timed */
97 double cycles; /**< the fastest time for this setup in cycles */
100 /*! \brief After 50 nstlist periods of not observing imbalance: never tune PME */
101 const int PMETunePeriod = 50;
102 /*! \brief Trigger PME load balancing at more than 5% PME overload */
103 const real loadBalanceTriggerFactor = 1.05;
104 /*! \brief Scale the grid by a most at factor 1.7.
106 * This still leaves room for about 4-4.5x decrease in grid spacing while limiting the cases where
107 * large imbalance leads to extreme cutoff scaling for marginal benefits.
109 * This should help to avoid:
110 * - large increase in power consumption for little performance gain
111 * - increasing communication volume
114 const real c_maxSpacingScaling = 1.7;
115 /*! \brief In the initial scan, step by grids that are at least a factor 0.8 coarser */
116 const real gridpointsScaleFactor = 0.8;
117 /*! \brief In the initial scan, try to skip grids with uneven x/y/z spacing,
118 * checking if the "efficiency" is more than 5% worse than the previous grid.
120 const real relativeEfficiencyFactor = 1.05;
121 /*! \brief Rerun until a run is 12% slower setups than the fastest run so far */
122 const real maxRelativeSlowdownAccepted = 1.12;
123 /*! \brief If setups get more than 2% faster, do another round to avoid
124 * choosing a slower setup due to acceleration or fluctuations.
126 const real maxFluctuationAccepted = 1.02;
128 //! \brief Number of nstlist long tuning intervals to skip before starting
129 // load-balancing at the beginning of the run.
130 const int c_numFirstTuningIntervalSkip = 5;
131 //! \brief Number of nstlist long tuning intervals to skip before starting
132 // load-balancing at the beginning of the run with separate PME ranks. */
133 const int c_numFirstTuningIntervalSkipWithSepPme = 3;
134 //! \brief Number of nstlist long tuning intervals to skip after switching to a new setting
136 const int c_numPostSwitchTuningIntervalSkip = 1;
137 //! \brief Number of seconds to delay the tuning at startup to allow processors clocks to ramp up.
138 const double c_startupTimeDelay = 5.0;
140 /*! \brief Enumeration whose values describe the effect limiting the load balancing */
151 /*! \brief Descriptive strings matching ::epmelb */
152 static const char* pmelblim_str[epmelblimNR] = { "no", "box size", "domain decompostion",
153 "PME grid restriction",
154 "maximum allowed grid scaling" };
156 struct pme_load_balancing_t
158 gmx_bool bSepPMERanks; /**< do we have separate PME ranks? */
159 gmx_bool bActive; /**< is PME tuning active? */
160 int64_t step_rel_stop; /**< stop the tuning after this value of step_rel */
161 gmx_bool bTriggerOnDLB; /**< trigger balancing only on DD DLB */
162 gmx_bool bBalance; /**< are we in the balancing phase, i.e. trying different setups? */
163 int nstage; /**< the current maximum number of stages */
165 real cut_spacing; /**< the minimum cutoff / PME grid spacing ratio */
166 real rcut_vdw; /**< Vdw cutoff (does not change) */
167 real rcut_coulomb_start; /**< Initial electrostatics cutoff */
168 real rbufOuter_coulomb; /**< the outer pairlist buffer size */
169 real rbufOuter_vdw; /**< the outer pairlist buffer size */
170 real rbufInner_coulomb; /**< the inner pairlist buffer size */
171 real rbufInner_vdw; /**< the inner pairlist buffer size */
172 matrix box_start; /**< the initial simulation box */
173 std::vector<pme_setup_t> setup; /**< the PME+cutoff setups */
174 int cur; /**< the index (in setup) of the current setup */
175 int fastest; /**< index of the fastest setup up till now */
176 int lower_limit; /**< don't go below this setup index */
177 int start; /**< start of setup index range to consider in stage>0 */
178 int end; /**< end of setup index range to consider in stage>0 */
179 int elimited; /**< was the balancing limited, uses enum above */
180 int cutoff_scheme; /**< Verlet or group cut-offs */
182 int stage; /**< the current stage */
184 int cycles_n; /**< step cycle counter cumulative count */
185 double cycles_c; /**< step cycle counter cumulative cycles */
186 double startTime; /**< time stamp when the balancing was started (relative to the UNIX epoch start).*/
189 /* TODO The code in this file should call this getter, rather than
190 * read bActive anywhere */
191 bool pme_loadbal_is_active(const pme_load_balancing_t* pme_lb)
193 return pme_lb != nullptr && pme_lb->bActive;
196 // TODO Return a unique_ptr to pme_load_balancing_t
197 void pme_loadbal_init(pme_load_balancing_t** pme_lb_p,
199 const gmx::MDLogger& mdlog,
200 const t_inputrec& ir,
202 const interaction_const_t& ic,
203 const nonbonded_verlet_t& nbv,
208 pme_load_balancing_t* pme_lb;
212 // Note that we don't (yet) support PME load balancing with LJ-PME only.
213 GMX_RELEASE_ASSERT(EEL_PME(ir.coulombtype),
214 "pme_loadbal_init called without PME electrostatics");
215 // To avoid complexity, we require a single cut-off with PME for q+LJ.
216 // This is checked by grompp, but it doesn't hurt to check again.
217 GMX_RELEASE_ASSERT(!(EEL_PME(ir.coulombtype) && EVDW_PME(ir.vdwtype) && ir.rcoulomb != ir.rvdw),
218 "With Coulomb and LJ PME, rcoulomb should be equal to rvdw");
220 pme_lb = new pme_load_balancing_t;
222 pme_lb->bSepPMERanks = !thisRankHasDuty(cr, DUTY_PME);
224 /* Initially we turn on balancing directly on based on PP/PME imbalance */
225 pme_lb->bTriggerOnDLB = FALSE;
227 /* Any number of stages >= 2 is supported */
230 pme_lb->cutoff_scheme = ir.cutoff_scheme;
232 pme_lb->rbufOuter_coulomb = nbv.pairlistOuterRadius() - ic.rcoulomb;
233 pme_lb->rbufOuter_vdw = nbv.pairlistOuterRadius() - ic.rvdw;
234 pme_lb->rbufInner_coulomb = nbv.pairlistInnerRadius() - ic.rcoulomb;
235 pme_lb->rbufInner_vdw = nbv.pairlistInnerRadius() - ic.rvdw;
237 /* Scale box with Ewald wall factor; note that we pmedata->boxScaler
238 * can't always usedd as it's not available with separate PME ranks.
240 EwaldBoxZScaler boxScaler(ir);
241 boxScaler.scaleBox(box, pme_lb->box_start);
243 pme_lb->setup.resize(1);
245 pme_lb->rcut_vdw = ic.rvdw;
246 pme_lb->rcut_coulomb_start = ir.rcoulomb;
249 pme_lb->setup[0].rcut_coulomb = ic.rcoulomb;
250 pme_lb->setup[0].rlistOuter = nbv.pairlistOuterRadius();
251 pme_lb->setup[0].rlistInner = nbv.pairlistInnerRadius();
252 pme_lb->setup[0].grid[XX] = ir.nkx;
253 pme_lb->setup[0].grid[YY] = ir.nky;
254 pme_lb->setup[0].grid[ZZ] = ir.nkz;
255 pme_lb->setup[0].ewaldcoeff_q = ic.ewaldcoeff_q;
256 pme_lb->setup[0].ewaldcoeff_lj = ic.ewaldcoeff_lj;
258 if (!pme_lb->bSepPMERanks)
260 GMX_RELEASE_ASSERT(pmedata,
261 "On ranks doing both PP and PME we need a valid pmedata object");
262 pme_lb->setup[0].pmedata = pmedata;
266 for (d = 0; d < DIM; d++)
268 sp = norm(pme_lb->box_start[d]) / pme_lb->setup[0].grid[d];
274 pme_lb->setup[0].spacing = spm;
276 if (ir.fourier_spacing > 0)
278 pme_lb->cut_spacing = ir.rcoulomb / ir.fourier_spacing;
282 pme_lb->cut_spacing = ir.rcoulomb / pme_lb->setup[0].spacing;
288 pme_lb->lower_limit = 0;
291 pme_lb->elimited = epmelblimNO;
293 pme_lb->cycles_n = 0;
294 pme_lb->cycles_c = 0;
295 pme_lb->startTime = gmx_gettime();
297 if (!wallcycle_have_counter())
299 GMX_LOG(mdlog.warning)
302 "NOTE: Cycle counters unsupported or not enabled in kernel. Cannot use "
303 "PME-PP balancing.");
306 /* Tune with GPUs and/or separate PME ranks.
307 * When running only on a CPU without PME ranks, PME tuning will only help
308 * with small numbers of atoms in the cut-off sphere.
310 pme_lb->bActive = (wallcycle_have_counter() && (bUseGPU || pme_lb->bSepPMERanks));
312 /* With GPUs and no separate PME ranks we can't measure the PP/PME
313 * imbalance, so we start balancing right away.
314 * Otherwise we only start balancing after we observe imbalance.
316 pme_lb->bBalance = (pme_lb->bActive && (bUseGPU && !pme_lb->bSepPMERanks));
318 pme_lb->step_rel_stop = PMETunePeriod * ir.nstlist;
320 /* Delay DD load balancing when GPUs are used */
321 if (pme_lb->bActive && DOMAINDECOMP(cr) && cr->dd->nnodes > 1 && bUseGPU)
323 /* Lock DLB=auto to off (does nothing when DLB=yes/no.
324 * With GPUs and separate PME nodes, we want to first
325 * do PME tuning without DLB, since DLB might limit
326 * the cut-off, which never improves performance.
327 * We allow for DLB + PME tuning after a first round of tuning.
330 if (dd_dlb_is_locked(cr->dd))
332 GMX_LOG(mdlog.warning)
334 .appendText("NOTE: DLB will not turn on during the first phase of PME tuning");
341 /*! \brief Try to increase the cutoff during load balancing */
342 static gmx_bool pme_loadbal_increase_cutoff(pme_load_balancing_t* pme_lb, int pme_order, const gmx_domdec_t* dd)
345 real tmpr_coulomb, tmpr_vdw;
349 /* Try to add a new setup with next larger cut-off to the list */
352 set.pmedata = nullptr;
354 NumPmeDomains numPmeDomains = getNumPmeDomains(dd);
359 /* Avoid infinite while loop, which can occur at the minimum grid size.
360 * Note that in practice load balancing will stop before this point.
361 * The factor 2.1 allows for the extreme case in which only grids
362 * of powers of 2 are allowed (the current code supports more grids).
370 clear_ivec(set.grid);
371 sp = calcFftGrid(nullptr, pme_lb->box_start, fac * pme_lb->setup[pme_lb->cur].spacing,
372 minimalPmeGridSize(pme_order), &set.grid[XX], &set.grid[YY], &set.grid[ZZ]);
374 /* As here we can't easily check if one of the PME ranks
375 * uses threading, we do a conservative grid check.
376 * This means we can't use pme_order or less grid lines
377 * per PME rank along x, which is not a strong restriction.
379 grid_ok = gmx_pme_check_restrictions(pme_order, set.grid[XX], set.grid[YY], set.grid[ZZ],
380 numPmeDomains.x, true, false);
381 } while (sp <= 1.001 * pme_lb->setup[pme_lb->cur].spacing || !grid_ok);
383 set.rcut_coulomb = pme_lb->cut_spacing * sp;
384 if (set.rcut_coulomb < pme_lb->rcut_coulomb_start)
386 /* This is unlikely, but can happen when e.g. continuing from
387 * a checkpoint after equilibration where the box shrank a lot.
388 * We want to avoid rcoulomb getting smaller than rvdw
389 * and there might be more issues with decreasing rcoulomb.
391 set.rcut_coulomb = pme_lb->rcut_coulomb_start;
394 if (pme_lb->cutoff_scheme == ecutsVERLET)
396 /* Never decrease the Coulomb and VdW list buffers */
397 set.rlistOuter = std::max(set.rcut_coulomb + pme_lb->rbufOuter_coulomb,
398 pme_lb->rcut_vdw + pme_lb->rbufOuter_vdw);
399 set.rlistInner = std::max(set.rcut_coulomb + pme_lb->rbufInner_coulomb,
400 pme_lb->rcut_vdw + pme_lb->rbufInner_vdw);
404 /* TODO Remove these lines and pme_lb->cutoff_scheme */
405 tmpr_coulomb = set.rcut_coulomb + pme_lb->rbufOuter_coulomb;
406 tmpr_vdw = pme_lb->rcut_vdw + pme_lb->rbufOuter_vdw;
407 /* Two (known) bugs with cutoff-scheme=group here:
408 * - This modification of rlist results in incorrect DD comunication.
409 * - We should set fr->bTwinRange = (fr->rlistlong > fr->rlist).
411 set.rlistOuter = std::min(tmpr_coulomb, tmpr_vdw);
412 set.rlistInner = set.rlistOuter;
416 /* The grid efficiency is the size wrt a grid with uniform x/y/z spacing */
417 set.grid_efficiency = 1;
418 for (d = 0; d < DIM; d++)
420 set.grid_efficiency *= (set.grid[d] * sp) / norm(pme_lb->box_start[d]);
422 /* The Ewald coefficient is inversly proportional to the cut-off */
423 set.ewaldcoeff_q = pme_lb->setup[0].ewaldcoeff_q * pme_lb->setup[0].rcut_coulomb / set.rcut_coulomb;
424 /* We set ewaldcoeff_lj in set, even when LJ-PME is not used */
425 set.ewaldcoeff_lj = pme_lb->setup[0].ewaldcoeff_lj * pme_lb->setup[0].rcut_coulomb / set.rcut_coulomb;
432 fprintf(debug, "PME loadbal: grid %d %d %d, coulomb cutoff %f\n", set.grid[XX],
433 set.grid[YY], set.grid[ZZ], set.rcut_coulomb);
435 pme_lb->setup.push_back(set);
439 /*! \brief Print the PME grid */
440 static void print_grid(FILE* fp_err, FILE* fp_log, const char* pre, const char* desc, const pme_setup_t* set, double cycles)
442 auto buf = gmx::formatString("%-11s%10s pme grid %d %d %d, coulomb cutoff %.3f", pre, desc,
443 set->grid[XX], set->grid[YY], set->grid[ZZ], set->rcut_coulomb);
446 buf += gmx::formatString(": %.1f M-cycles", cycles * 1e-6);
448 if (fp_err != nullptr)
450 fprintf(fp_err, "\r%s\n", buf.c_str());
453 if (fp_log != nullptr)
455 fprintf(fp_log, "%s\n", buf.c_str());
459 /*! \brief Return the index of the last setup used in PME load balancing */
460 static int pme_loadbal_end(pme_load_balancing_t* pme_lb)
462 /* In the initial stage only n is set; end is not set yet */
469 return pme_lb->setup.size();
473 /*! \brief Print descriptive string about what limits PME load balancing */
474 static void print_loadbal_limited(FILE* fp_err, FILE* fp_log, int64_t step, pme_load_balancing_t* pme_lb)
476 auto buf = gmx::formatString(
477 "step %4s: the %s limits the PME load balancing to a coulomb cut-off of %.3f",
478 gmx::int64ToString(step).c_str(), pmelblim_str[pme_lb->elimited],
479 pme_lb->setup[pme_loadbal_end(pme_lb) - 1].rcut_coulomb);
480 if (fp_err != nullptr)
482 fprintf(fp_err, "\r%s\n", buf.c_str());
485 if (fp_log != nullptr)
487 fprintf(fp_log, "%s\n", buf.c_str());
491 /*! \brief Switch load balancing to stage 1
493 * In this stage, only reasonably fast setups are run again. */
494 static void switch_to_stage1(pme_load_balancing_t* pme_lb)
496 /* Increase start until we find a setup that is not slower than
497 * maxRelativeSlowdownAccepted times the fastest setup.
499 pme_lb->start = pme_lb->lower_limit;
500 while (pme_lb->start + 1 < gmx::ssize(pme_lb->setup)
501 && (pme_lb->setup[pme_lb->start].count == 0
502 || pme_lb->setup[pme_lb->start].cycles
503 > pme_lb->setup[pme_lb->fastest].cycles * maxRelativeSlowdownAccepted))
507 /* While increasing start, we might have skipped setups that we did not
508 * time during stage 0. We want to extend the range for stage 1 to include
509 * any skipped setups that lie between setups that were measured to be
510 * acceptably fast and too slow.
512 while (pme_lb->start > pme_lb->lower_limit && pme_lb->setup[pme_lb->start - 1].count == 0)
517 /* Decrease end only with setups that we timed and that are slow. */
518 pme_lb->end = pme_lb->setup.size();
519 if (pme_lb->setup[pme_lb->end - 1].count > 0
520 && pme_lb->setup[pme_lb->end - 1].cycles
521 > pme_lb->setup[pme_lb->fastest].cycles * maxRelativeSlowdownAccepted)
528 /* Next we want to choose setup pme_lb->end-1, but as we will decrease
529 * pme_lb->cur by one right after returning, we set cur to end.
531 pme_lb->cur = pme_lb->end;
534 /*! \brief Process the timings and try to adjust the PME grid and Coulomb cut-off
536 * The adjustment is done to generate a different non-bonded PP and PME load.
537 * With separate PME ranks (PP and PME on different processes) or with
538 * a GPU (PP on GPU, PME on CPU), PP and PME run on different resources
539 * and changing the load will affect the load balance and performance.
540 * The total time for a set of integration steps is monitored and a range
541 * of grid/cut-off setups is scanned. After calling pme_load_balance many
542 * times and acquiring enough statistics, the best performing setup is chosen.
543 * Here we try to take into account fluctuations and changes due to external
544 * factors as well as DD load balancing.
546 static void pme_load_balance(pme_load_balancing_t* pme_lb,
550 const gmx::MDLogger& mdlog,
551 const t_inputrec& ir,
553 gmx::ArrayRef<const gmx::RVec> x,
555 interaction_const_t* ic,
556 struct nonbonded_verlet_t* nbv,
557 struct gmx_pme_t** pmedata,
563 char buf[STRLEN], sbuf[22];
567 gmx_sumd(1, &cycles, cr);
568 cycles /= cr->nnodes;
571 set = &pme_lb->setup[pme_lb->cur];
574 /* Skip the first c_numPostSwitchTuningIntervalSkip cycles because the first step
575 * after a switch is much slower due to allocation and/or caching effects.
577 if (set->count % (c_numPostSwitchTuningIntervalSkip + 1) != 0)
582 sprintf(buf, "step %4s: ", gmx_step_str(step, sbuf));
583 print_grid(fp_err, fp_log, buf, "timed with", set, cycles);
585 GMX_RELEASE_ASSERT(set->count > c_numPostSwitchTuningIntervalSkip, "We should skip cycles");
586 if (set->count == (c_numPostSwitchTuningIntervalSkip + 1))
588 set->cycles = cycles;
592 if (cycles * maxFluctuationAccepted < set->cycles && pme_lb->stage == pme_lb->nstage - 1)
594 /* The performance went up a lot (due to e.g. DD load balancing).
595 * Add a stage, keep the minima, but rescan all setups.
602 "The performance for grid %d %d %d went from %.3f to %.1f M-cycles, this "
604 "Increased the number stages to %d"
605 " and ignoring the previous performance\n",
606 set->grid[XX], set->grid[YY], set->grid[ZZ], set->cycles * 1e-6,
607 cycles * 1e-6, maxFluctuationAccepted, pme_lb->nstage);
610 set->cycles = std::min(set->cycles, cycles);
613 if (set->cycles < pme_lb->setup[pme_lb->fastest].cycles)
615 pme_lb->fastest = pme_lb->cur;
617 if (DOMAINDECOMP(cr))
619 /* We found a new fastest setting, ensure that with subsequent
620 * shorter cut-off's the dynamic load balancing does not make
621 * the use of the current cut-off impossible. This solution is
622 * a trade-off, as the PME load balancing and DD domain size
623 * load balancing can interact in complex ways.
624 * With the Verlet kernels, DD load imbalance will usually be
625 * mainly due to bonded interaction imbalance, which will often
626 * quickly push the domain boundaries beyond the limit for the
627 * optimal, PME load balanced, cut-off. But it could be that
628 * better overal performance can be obtained with a slightly
629 * shorter cut-off and better DD load balancing.
631 set_dd_dlb_max_cutoff(cr, pme_lb->setup[pme_lb->fastest].rlistOuter);
634 cycles_fast = pme_lb->setup[pme_lb->fastest].cycles;
636 /* Check in stage 0 if we should stop scanning grids.
637 * Stop when the time is more than maxRelativeSlowDownAccepted longer than the fastest.
639 if (pme_lb->stage == 0 && pme_lb->cur > 0
640 && cycles > pme_lb->setup[pme_lb->fastest].cycles * maxRelativeSlowdownAccepted)
642 pme_lb->setup.resize(pme_lb->cur + 1);
643 /* Done with scanning, go to stage 1 */
644 switch_to_stage1(pme_lb);
647 if (pme_lb->stage == 0)
651 gridsize_start = set->grid[XX] * set->grid[YY] * set->grid[ZZ];
655 if (pme_lb->cur + 1 < gmx::ssize(pme_lb->setup))
657 /* We had already generated the next setup */
662 /* Find the next setup */
663 OK = pme_loadbal_increase_cutoff(pme_lb, ir.pme_order, cr->dd);
667 pme_lb->elimited = epmelblimPMEGRID;
672 && pme_lb->setup[pme_lb->cur + 1].spacing > c_maxSpacingScaling * pme_lb->setup[0].spacing)
675 pme_lb->elimited = epmelblimMAXSCALING;
678 if (OK && ir.ePBC != epbcNONE)
680 OK = (gmx::square(pme_lb->setup[pme_lb->cur + 1].rlistOuter) <= max_cutoff2(ir.ePBC, box));
683 pme_lb->elimited = epmelblimBOX;
691 if (DOMAINDECOMP(cr))
693 OK = change_dd_cutoff(cr, box, x, pme_lb->setup[pme_lb->cur].rlistOuter);
696 /* Failed: do not use this setup */
698 pme_lb->elimited = epmelblimDD;
704 /* We hit the upper limit for the cut-off,
705 * the setup should not go further than cur.
707 pme_lb->setup.resize(pme_lb->cur + 1);
708 print_loadbal_limited(fp_err, fp_log, step, pme_lb);
709 /* Switch to the next stage */
710 switch_to_stage1(pme_lb);
713 && !(pme_lb->setup[pme_lb->cur].grid[XX] * pme_lb->setup[pme_lb->cur].grid[YY]
714 * pme_lb->setup[pme_lb->cur].grid[ZZ]
715 < gridsize_start * gridpointsScaleFactor
716 && pme_lb->setup[pme_lb->cur].grid_efficiency
717 < pme_lb->setup[pme_lb->cur - 1].grid_efficiency * relativeEfficiencyFactor));
720 if (pme_lb->stage > 0 && pme_lb->end == 1)
722 pme_lb->cur = pme_lb->lower_limit;
723 pme_lb->stage = pme_lb->nstage;
725 else if (pme_lb->stage > 0 && pme_lb->end > 1)
727 /* If stage = nstage-1:
728 * scan over all setups, rerunning only those setups
729 * which are not much slower than the fastest
732 * Note that we loop backward to minimize the risk of the cut-off
733 * getting limited by DD DLB, since the DLB cut-off limit is set
734 * to the fastest PME setup.
738 if (pme_lb->cur > pme_lb->start)
746 pme_lb->cur = pme_lb->end - 1;
748 } while (pme_lb->stage == pme_lb->nstage - 1 && pme_lb->setup[pme_lb->cur].count > 0
749 && pme_lb->setup[pme_lb->cur].cycles > cycles_fast * maxRelativeSlowdownAccepted);
751 if (pme_lb->stage == pme_lb->nstage)
753 /* We are done optimizing, use the fastest setup we found */
754 pme_lb->cur = pme_lb->fastest;
758 if (DOMAINDECOMP(cr) && pme_lb->stage > 0)
760 OK = change_dd_cutoff(cr, box, x, pme_lb->setup[pme_lb->cur].rlistOuter);
763 /* For some reason the chosen cut-off is incompatible with DD.
764 * We should continue scanning a more limited range of cut-off's.
766 if (pme_lb->cur > 1 && pme_lb->stage == pme_lb->nstage)
768 /* stage=nstage says we're finished, but we should continue
769 * balancing, so we set back stage which was just incremented.
773 if (pme_lb->cur <= pme_lb->fastest)
775 /* This should not happen, as we set limits on the DLB bounds.
776 * But we implement a complete failsafe solution anyhow.
778 GMX_LOG(mdlog.warning)
780 .appendTextFormatted(
781 "The fastest PP/PME load balancing setting (cutoff %.3d nm) is no "
782 "longer available due to DD DLB or box size limitations",
784 pme_lb->fastest = pme_lb->lower_limit;
785 pme_lb->start = pme_lb->lower_limit;
787 /* Limit the range to below the current cut-off, scan from start */
788 pme_lb->end = pme_lb->cur;
789 pme_lb->cur = pme_lb->start;
790 pme_lb->elimited = epmelblimDD;
791 print_loadbal_limited(fp_err, fp_log, step, pme_lb);
795 /* Change the Coulomb cut-off and the PME grid */
797 set = &pme_lb->setup[pme_lb->cur];
799 ic->rcoulomb = set->rcut_coulomb;
800 nbv->changePairlistRadii(set->rlistOuter, set->rlistInner);
801 ic->ewaldcoeff_q = set->ewaldcoeff_q;
802 /* TODO: centralize the code that sets the potentials shifts */
803 if (ic->coulomb_modifier == eintmodPOTSHIFT)
805 GMX_RELEASE_ASSERT(ic->rcoulomb != 0, "Cutoff radius cannot be zero");
806 ic->sh_ewald = std::erfc(ic->ewaldcoeff_q * ic->rcoulomb) / ic->rcoulomb;
808 if (EVDW_PME(ic->vdwtype))
810 /* We have PME for both Coulomb and VdW, set rvdw equal to rcoulomb */
811 ic->rvdw = set->rcut_coulomb;
812 ic->ewaldcoeff_lj = set->ewaldcoeff_lj;
813 if (ic->vdw_modifier == eintmodPOTSHIFT)
817 ic->dispersion_shift.cpot = -1.0 / gmx::power6(static_cast<double>(ic->rvdw));
818 ic->repulsion_shift.cpot = -1.0 / gmx::power12(static_cast<double>(ic->rvdw));
819 crc2 = gmx::square(ic->ewaldcoeff_lj * ic->rvdw);
821 (std::exp(-crc2) * (1 + crc2 + 0.5 * crc2 * crc2) - 1) / gmx::power6(ic->rvdw);
825 /* We always re-initialize the tables whether they are used or not */
826 init_interaction_const_tables(nullptr, ic);
828 Nbnxm::gpu_pme_loadbal_update_param(nbv, ic);
830 if (!pme_lb->bSepPMERanks)
833 * CPU PME keeps a list of allocated pmedata's, that's why pme_lb->setup[pme_lb->cur].pmedata is not always nullptr.
834 * GPU PME, however, currently needs the gmx_pme_reinit always called on load balancing
835 * (pme_gpu_reinit might be not sufficiently decoupled from gmx_pme_init).
836 * This can lead to a lot of reallocations for PME GPU.
837 * Would be nicer if the allocated grid list was hidden within a single pmedata structure.
839 if ((pme_lb->setup[pme_lb->cur].pmedata == nullptr)
840 || pme_gpu_task_enabled(pme_lb->setup[pme_lb->cur].pmedata))
842 /* Generate a new PME data structure,
843 * copying part of the old pointers.
845 gmx_pme_reinit(&set->pmedata, cr, pme_lb->setup[0].pmedata, &ir, set->grid,
846 set->ewaldcoeff_q, set->ewaldcoeff_lj);
848 *pmedata = set->pmedata;
852 /* Tell our PME-only rank to switch grid */
853 gmx_pme_send_switchgrid(cr, set->grid, set->ewaldcoeff_q, set->ewaldcoeff_lj);
858 print_grid(nullptr, debug, "", "switched to", set, -1);
861 if (pme_lb->stage == pme_lb->nstage)
863 print_grid(fp_err, fp_log, "", "optimal", set, -1);
867 /*! \brief Prepare for another round of PME load balancing
869 * \param[in,out] pme_lb Pointer to PME load balancing struct
870 * \param[in] bDlbUnlocked TRUE is DLB was locked and is now unlocked
872 * If the conditions (e.g. DLB off/on, CPU/GPU throttling etc.) changed,
873 * the PP/PME balance might change and re-balancing can improve performance.
874 * This function adds 2 stages and adjusts the considered setup range.
876 static void continue_pme_loadbal(pme_load_balancing_t* pme_lb, gmx_bool bDlbUnlocked)
878 /* Add 2 tuning stages, keep the detected end of the setup range */
880 if (bDlbUnlocked && pme_lb->bSepPMERanks)
882 /* With separate PME ranks, DLB should always lower the PP load and
883 * can only increase the PME load (more communication and imbalance),
884 * so we only need to scan longer cut-off's.
886 pme_lb->lower_limit = pme_lb->cur;
888 pme_lb->start = pme_lb->lower_limit;
891 void pme_loadbal_do(pme_load_balancing_t* pme_lb,
895 const gmx::MDLogger& mdlog,
896 const t_inputrec& ir,
899 gmx::ArrayRef<const gmx::RVec> x,
900 gmx_wallcycle_t wcycle,
904 bool useGpuPmePpCommunication)
909 assert(pme_lb != nullptr);
911 if (!pme_lb->bActive)
916 n_prev = pme_lb->cycles_n;
917 cycles_prev = pme_lb->cycles_c;
918 wallcycle_get(wcycle, ewcSTEP, &pme_lb->cycles_n, &pme_lb->cycles_c);
920 /* Before the first step we haven't done any steps yet.
921 * Also handle cases where ir.init_step % ir.nstlist != 0.
922 * We also want to skip a number of steps and seconds while
923 * the CPU and GPU, when used, performance stabilizes.
925 if (pme_lb->cycles_n == 0 || step_rel < c_numFirstTuningIntervalSkip * ir.nstlist
926 || gmx_gettime() - pme_lb->startTime < c_startupTimeDelay)
932 /* Sanity check, we expect nstlist cycle counts */
933 if (pme_lb->cycles_n - n_prev != ir.nstlist)
935 /* We could return here, but it's safer to issue an error and quit */
936 gmx_incons("pme_loadbal_do called at an interval != nstlist");
939 /* PME grid + cut-off optimization with GPUs or PME ranks */
940 if (!pme_lb->bBalance && pme_lb->bSepPMERanks)
942 if (pme_lb->bTriggerOnDLB)
944 pme_lb->bBalance = dd_dlb_is_on(cr->dd);
946 /* We should ignore the first timing to avoid timing allocation
947 * overhead. And since the PME load balancing is called just
948 * before DD repartitioning, the ratio returned by dd_pme_f_ratio
949 * is not over the last nstlist steps, but the nstlist steps before
950 * that. So the first useful ratio is available at step_rel=3*nstlist.
952 else if (step_rel >= c_numFirstTuningIntervalSkipWithSepPme * ir.nstlist)
954 if (DDMASTER(cr->dd))
956 /* If PME rank load is too high, start tuning. If
957 PME-PP direct GPU communication is active,
958 unconditionally start tuning since ratio will be
959 unreliable due to CPU-GPU asynchronicity in codepath */
960 pme_lb->bBalance = useGpuPmePpCommunication
962 : (dd_pme_f_ratio(cr->dd) >= loadBalanceTriggerFactor);
964 dd_bcast(cr->dd, sizeof(gmx_bool), &pme_lb->bBalance);
967 pme_lb->bActive = (pme_lb->bBalance || step_rel <= pme_lb->step_rel_stop);
970 /* The location in the code of this balancing termination is strange.
971 * You would expect to have it after the call to pme_load_balance()
972 * below, since there pme_lb->stage is updated.
973 * But when terminating directly after deciding on and selecting the
974 * optimal setup, DLB will turn on right away if it was locked before.
975 * This might be due to PME reinitialization. So we check stage here
976 * to allow for another nstlist steps with DLB locked to stabilize
979 if (pme_lb->bBalance && pme_lb->stage == pme_lb->nstage)
981 pme_lb->bBalance = FALSE;
983 if (DOMAINDECOMP(cr) && dd_dlb_is_locked(cr->dd))
985 /* Unlock the DLB=auto, DLB is allowed to activate */
986 dd_dlb_unlock(cr->dd);
987 GMX_LOG(mdlog.warning)
989 .appendText("NOTE: DLB can now turn on, when beneficial");
991 /* We don't deactivate the tuning yet, since we will balance again
992 * after DLB gets turned on, if it does within PMETune_period.
994 continue_pme_loadbal(pme_lb, TRUE);
995 pme_lb->bTriggerOnDLB = TRUE;
996 pme_lb->step_rel_stop = step_rel + PMETunePeriod * ir.nstlist;
1000 /* We're completely done with PME tuning */
1001 pme_lb->bActive = FALSE;
1004 if (DOMAINDECOMP(cr))
1006 /* Set the cut-off limit to the final selected cut-off,
1007 * so we don't have artificial DLB limits.
1008 * This also ensures that we won't disable the currently
1009 * optimal setting during a second round of PME balancing.
1011 set_dd_dlb_max_cutoff(cr, fr->nbv->pairlistOuterRadius());
1015 if (pme_lb->bBalance)
1017 /* We might not have collected nstlist steps in cycles yet,
1018 * since init_step might not be a multiple of nstlist,
1019 * but the first data collected is skipped anyhow.
1021 pme_load_balance(pme_lb, cr, fp_err, fp_log, mdlog, ir, box, x,
1022 pme_lb->cycles_c - cycles_prev, fr->ic, fr->nbv.get(), &fr->pmedata, step);
1024 /* Update deprecated rlist in forcerec to stay in sync with fr->nbv */
1025 fr->rlist = fr->nbv->pairlistOuterRadius();
1027 if (ir.eDispCorr != edispcNO)
1029 fr->dispersionCorrection->setParameters(*fr->ic);
1033 if (!pme_lb->bBalance && (!pme_lb->bSepPMERanks || step_rel > pme_lb->step_rel_stop))
1035 /* We have just deactivated the balancing and we're not measuring PP/PME
1036 * imbalance during the first steps of the run: deactivate the tuning.
1038 pme_lb->bActive = FALSE;
1041 if (!(pme_lb->bActive) && DOMAINDECOMP(cr) && dd_dlb_is_locked(cr->dd))
1043 /* Make sure DLB is allowed when we deactivate PME tuning */
1044 dd_dlb_unlock(cr->dd);
1045 GMX_LOG(mdlog.warning)
1047 .appendText("NOTE: DLB can now turn on, when beneficial");
1050 *bPrinting = pme_lb->bBalance;
1053 /*! \brief Return product of the number of PME grid points in each dimension */
1054 static int pme_grid_points(const pme_setup_t* setup)
1056 return setup->grid[XX] * setup->grid[YY] * setup->grid[ZZ];
1059 /*! \brief Print one load-balancing setting */
1060 static void print_pme_loadbal_setting(FILE* fplog, const char* name, const pme_setup_t* setup)
1062 fprintf(fplog, " %-7s %6.3f nm %6.3f nm %3d %3d %3d %5.3f nm %5.3f nm\n", name,
1063 setup->rcut_coulomb, setup->rlistInner, setup->grid[XX], setup->grid[YY],
1064 setup->grid[ZZ], setup->spacing, 1 / setup->ewaldcoeff_q);
1067 /*! \brief Print all load-balancing settings */
1068 static void print_pme_loadbal_settings(pme_load_balancing_t* pme_lb,
1070 const gmx::MDLogger& mdlog,
1071 gmx_bool bNonBondedOnGPU)
1073 double pp_ratio, grid_ratio;
1074 real pp_ratio_temporary;
1076 pp_ratio_temporary = pme_lb->setup[pme_lb->cur].rlistInner / pme_lb->setup[0].rlistInner;
1077 pp_ratio = gmx::power3(pp_ratio_temporary);
1078 grid_ratio = pme_grid_points(&pme_lb->setup[pme_lb->cur])
1079 / static_cast<double>(pme_grid_points(&pme_lb->setup[0]));
1081 fprintf(fplog, "\n");
1082 fprintf(fplog, " P P - P M E L O A D B A L A N C I N G\n");
1083 fprintf(fplog, "\n");
1084 /* Here we only warn when the optimal setting is the last one */
1085 if (pme_lb->elimited != epmelblimNO && pme_lb->cur == pme_loadbal_end(pme_lb) - 1)
1087 fprintf(fplog, " NOTE: The PP/PME load balancing was limited by the %s,\n",
1088 pmelblim_str[pme_lb->elimited]);
1089 fprintf(fplog, " you might not have reached a good load balance.\n");
1090 if (pme_lb->elimited == epmelblimDD)
1092 fprintf(fplog, " Try different mdrun -dd settings or lower the -dds value.\n");
1094 fprintf(fplog, "\n");
1096 fprintf(fplog, " PP/PME load balancing changed the cut-off and PME settings:\n");
1097 fprintf(fplog, " particle-particle PME\n");
1098 fprintf(fplog, " rcoulomb rlist grid spacing 1/beta\n");
1099 print_pme_loadbal_setting(fplog, "initial", &pme_lb->setup[0]);
1100 print_pme_loadbal_setting(fplog, "final", &pme_lb->setup[pme_lb->cur]);
1101 fprintf(fplog, " cost-ratio %4.2f %4.2f\n", pp_ratio, grid_ratio);
1102 fprintf(fplog, " (note that these numbers concern only part of the total PP and PME load)\n");
1104 if (pp_ratio > 1.5 && !bNonBondedOnGPU)
1106 GMX_LOG(mdlog.warning)
1109 "NOTE: PME load balancing increased the non-bonded workload by more than "
1111 " For better performance, use (more) PME ranks (mdrun -npme),\n"
1112 " or if you are beyond the scaling limit, use fewer total ranks (or "
1117 fprintf(fplog, "\n");
1121 void pme_loadbal_done(pme_load_balancing_t* pme_lb, FILE* fplog, const gmx::MDLogger& mdlog, gmx_bool bNonBondedOnGPU)
1123 if (fplog != nullptr && (pme_lb->cur > 0 || pme_lb->elimited != epmelblimNO))
1125 print_pme_loadbal_settings(pme_lb, fplog, mdlog, bNonBondedOnGPU);