static void prepare_verlet_scheme(FILE *fplog,
t_commrec *cr,
t_inputrec *ir,
int nstlist_cmdline,
const gmx_mtop_t *mtop,
matrix box,
gmx_bool bUseGPU)
{
/* For NVE simulations, we will retain the initial list buffer */
if (EI_DYNAMICS(ir->eI) &&
ir->verletbuf_tol > 0 &&
!(EI_MD(ir->eI) && ir->etc == etcNO))
{
/* Update the Verlet buffer size for the current run setup */
verletbuf_list_setup_t ls;
real rlist_new;
/* Here we assume SIMD-enabled kernels are being used. But as currently
* calc_verlet_buffer_size gives the same results for 4x8 and 4x4
* and 4x2 gives a larger buffer than 4x4, this is ok.
*/
verletbuf_get_list_setup(TRUE, bUseGPU, &ls);
calc_verlet_buffer_size(mtop, det(box), ir, -1, &ls, NULL, &rlist_new);
if (rlist_new != ir->rlist)
{
if (fplog != NULL)
{
fprintf(fplog, "\nChanging rlist from %g to %g for non-bonded %dx%d atom kernels\n\n",
ir->rlist, rlist_new,
ls.cluster_size_i, ls.cluster_size_j);
}
ir->rlist = rlist_new;
ir->rlistlong = rlist_new;
}
}
if (nstlist_cmdline > 0 && (!EI_DYNAMICS(ir->eI) || ir->verletbuf_tol <= 0))
{
gmx_fatal(FARGS, "Can not set nstlist without %s",
!EI_DYNAMICS(ir->eI) ? "dynamics" : "verlet-buffer-tolerance");
}
if (EI_DYNAMICS(ir->eI))
{
/* Set or try nstlist values */
increase_nstlist(fplog, cr, ir, nstlist_cmdline, mtop, box, bUseGPU);
}
}
void calc_verlet_buffer_size(const gmx_mtop_t *mtop, real boxvol,
const t_inputrec *ir,
real reference_temperature,
const verletbuf_list_setup_t *list_setup,
int *n_nonlin_vsite,
real *rlist)
{
double resolution;
char *env;
real particle_distance;
real nb_clust_frac_pairs_not_in_list_at_cutoff;
verletbuf_atomtype_t *att = NULL;
int natt = -1, i;
double reppow;
real md1_ljd, d2_ljd, md3_ljd;
real md1_ljr, d2_ljr, md3_ljr;
real md1_el, d2_el;
real elfac;
real kT_fac, mass_min;
int ib0, ib1, ib;
real rb, rl;
real drift;
if (reference_temperature < 0)
{
if (EI_MD(ir->eI) && ir->etc == etcNO)
{
/* This case should be handled outside calc_verlet_buffer_size */
gmx_incons("calc_verlet_buffer_size called with an NVE ensemble and reference_temperature < 0");
}
/* We use the maximum temperature with multiple T-coupl groups.
* We could use a per particle temperature, but since particles
* interact, this might underestimate the buffer size.
*/
reference_temperature = 0;
for (i = 0; i < ir->opts.ngtc; i++)
{
if (ir->opts.tau_t[i] >= 0)
{
reference_temperature = max(reference_temperature,
ir->opts.ref_t[i]);
}
}
}
/* Resolution of the buffer size */
resolution = 0.001;
env = getenv("GMX_VERLET_BUFFER_RES");
if (env != NULL)
{
sscanf(env, "%lf", &resolution);
}
/* In an atom wise pair-list there would be no pairs in the list
* beyond the pair-list cut-off.
* However, we use a pair-list of groups vs groups of atoms.
* For groups of 4 atoms, the parallelism of SSE instructions, only
* 10% of the atoms pairs are not in the list just beyond the cut-off.
* As this percentage increases slowly compared to the decrease of the
* Gaussian displacement distribution over this range, we can simply
* reduce the drift by this fraction.
* For larger groups, e.g. of 8 atoms, this fraction will be lower,
* so then buffer size will be on the conservative (large) side.
*
* Note that the formulas used here do not take into account
* cancellation of errors which could occur by missing both
* attractive and repulsive interactions.
*
* The only major assumption is homogeneous particle distribution.
* For an inhomogeneous system, such as a liquid-vapor system,
* the buffer will be underestimated. The actual energy drift
* will be higher by the factor: local/homogeneous particle density.
*
* The results of this estimate have been checked againt simulations.
* In most cases the real drift differs by less than a factor 2.
*/
/* Worst case assumption: HCP packing of particles gives largest distance */
particle_distance = pow(boxvol*sqrt(2)/mtop->natoms, 1.0/3.0);
get_verlet_buffer_atomtypes(mtop, &att, &natt, n_nonlin_vsite);
assert(att != NULL && natt >= 0);
if (debug)
{
fprintf(debug, "particle distance assuming HCP packing: %f nm\n",
particle_distance);
fprintf(debug, "energy drift atom types: %d\n", natt);
}
reppow = mtop->ffparams.reppow;
md1_ljd = 0;
d2_ljd = 0;
md3_ljd = 0;
md1_ljr = 0;
d2_ljr = 0;
md3_ljr = 0;
if (ir->vdwtype == evdwCUT)
{
real sw_range, md3_pswf;
switch (ir->vdw_modifier)
{
case eintmodNONE:
case eintmodPOTSHIFT:
/* -dV/dr of -r^-6 and r^-reppow */
md1_ljd = -6*pow(ir->rvdw, -7.0);
md1_ljr = reppow*pow(ir->rvdw, -(reppow+1));
/* The contribution of the higher derivatives is negligible */
break;
case eintmodFORCESWITCH:
/* At the cut-off: V=V'=V''=0, so we use only V''' */
md3_ljd = -md3_force_switch(6.0, ir->rvdw_switch, ir->rvdw);
md3_ljr = md3_force_switch(reppow, ir->rvdw_switch, ir->rvdw);
break;
case eintmodPOTSWITCH:
/* At the cut-off: V=V'=V''=0.
* V''' is given by the original potential times
* the third derivative of the switch function.
*/
sw_range = ir->rvdw - ir->rvdw_switch;
md3_pswf = 60.0*pow(sw_range, -3.0);
md3_ljd = -pow(ir->rvdw, -6.0 )*md3_pswf;
md3_ljr = pow(ir->rvdw, -reppow)*md3_pswf;
break;
default:
gmx_incons("Unimplemented VdW modifier");
}
}
else if (EVDW_PME(ir->vdwtype))
{
real b, r, br, br2, br4, br6;
b = calc_ewaldcoeff_lj(ir->rvdw, ir->ewald_rtol_lj);
r = ir->rvdw;
br = b*r;
br2 = br*br;
br4 = br2*br2;
br6 = br4*br2;
/* -dV/dr of g(br)*r^-6 [where g(x) = exp(-x^2)(1+x^2+x^4/2), see LJ-PME equations in manual] and r^-reppow */
md1_ljd = -exp(-br2)*(br6 + 3.0*br4 + 6.0*br2 + 6.0)*pow(r, -7.0);
md1_ljr = reppow*pow(r, -(reppow+1));
/* The contribution of the higher derivatives is negligible */
}
else
{
gmx_fatal(FARGS, "Energy drift calculation is only implemented for plain cut-off Lennard-Jones interactions");
}
elfac = ONE_4PI_EPS0/ir->epsilon_r;
/* Determine md=-dV/dr and dd=d^2V/dr^2 */
md1_el = 0;
d2_el = 0;
if (ir->coulombtype == eelCUT || EEL_RF(ir->coulombtype))
{
real eps_rf, k_rf;
if (ir->coulombtype == eelCUT)
{
eps_rf = 1;
k_rf = 0;
}
else
{
eps_rf = ir->epsilon_rf/ir->epsilon_r;
if (eps_rf != 0)
{
k_rf = pow(ir->rcoulomb, -3.0)*(eps_rf - ir->epsilon_r)/(2*eps_rf + ir->epsilon_r);
}
else
{
/* epsilon_rf = infinity */
k_rf = 0.5*pow(ir->rcoulomb, -3.0);
}
}
if (eps_rf > 0)
{
md1_el = elfac*(pow(ir->rcoulomb, -2.0) - 2*k_rf*ir->rcoulomb);
}
d2_el = elfac*(2*pow(ir->rcoulomb, -3.0) + 2*k_rf);
}
else if (EEL_PME(ir->coulombtype) || ir->coulombtype == eelEWALD)
{
real b, rc, br;
b = calc_ewaldcoeff_q(ir->rcoulomb, ir->ewald_rtol);
rc = ir->rcoulomb;
br = b*rc;
md1_el = elfac*(b*exp(-br*br)*M_2_SQRTPI/rc + gmx_erfc(br)/(rc*rc));
d2_el = elfac/(rc*rc)*(2*b*(1 + br*br)*exp(-br*br)*M_2_SQRTPI + 2*gmx_erfc(br)/rc);
}
else
{
gmx_fatal(FARGS, "Energy drift calculation is only implemented for Reaction-Field and Ewald electrostatics");
}
/* Determine the variance of the atomic displacement
* over nstlist-1 steps: kT_fac
* For inertial dynamics (not Brownian dynamics) the mass factor
* is not included in kT_fac, it is added later.
*/
if (ir->eI == eiBD)
{
/* Get the displacement distribution from the random component only.
* With accurate integration the systematic (force) displacement
* should be negligible (unless nstlist is extremely large, which
* you wouldn't do anyhow).
*/
kT_fac = 2*BOLTZ*reference_temperature*(ir->nstlist-1)*ir->delta_t;
if (ir->bd_fric > 0)
{
/* This is directly sigma^2 of the displacement */
kT_fac /= ir->bd_fric;
/* Set the masses to 1 as kT_fac is the full sigma^2,
* but we divide by m in ener_drift().
*/
for (i = 0; i < natt; i++)
{
att[i].prop.mass = 1;
}
}
else
{
real tau_t;
/* Per group tau_t is not implemented yet, use the maximum */
tau_t = ir->opts.tau_t[0];
for (i = 1; i < ir->opts.ngtc; i++)
{
tau_t = max(tau_t, ir->opts.tau_t[i]);
}
kT_fac *= tau_t;
/* This kT_fac needs to be divided by the mass to get sigma^2 */
}
}
else
{
kT_fac = BOLTZ*reference_temperature*sqr((ir->nstlist-1)*ir->delta_t);
}
mass_min = att[0].prop.mass;
for (i = 1; i < natt; i++)
{
mass_min = min(mass_min, att[i].prop.mass);
}
if (debug)
{
fprintf(debug, "md1_ljd %9.2e d2_ljd %9.2e md3_ljd %9.2e\n", md1_ljd, d2_ljd, md3_ljd);
fprintf(debug, "md1_ljr %9.2e d2_ljr %9.2e md3_ljr %9.2e\n", md1_ljr, d2_ljr, md3_ljr);
fprintf(debug, "md1_el %9.2e d2_el %9.2e\n", md1_el, d2_el);
fprintf(debug, "sqrt(kT_fac) %f\n", sqrt(kT_fac));
fprintf(debug, "mass_min %f\n", mass_min);
}
/* Search using bisection */
ib0 = -1;
/* The drift will be neglible at 5 times the max sigma */
ib1 = (int)(5*2*sqrt(kT_fac/mass_min)/resolution) + 1;
while (ib1 - ib0 > 1)
{
ib = (ib0 + ib1)/2;
rb = ib*resolution;
rl = max(ir->rvdw, ir->rcoulomb) + rb;
/* Calculate the average energy drift at the last step
* of the nstlist steps at which the pair-list is used.
*/
drift = ener_drift(att, natt, &mtop->ffparams,
kT_fac,
md1_ljd, d2_ljd, md3_ljd,
md1_ljr, d2_ljr, md3_ljr,
md1_el, d2_el,
rb,
rl, boxvol);
/* Correct for the fact that we are using a Ni x Nj particle pair list
* and not a 1 x 1 particle pair list. This reduces the drift.
*/
/* We don't have a formula for 8 (yet), use 4 which is conservative */
nb_clust_frac_pairs_not_in_list_at_cutoff =
surface_frac(min(list_setup->cluster_size_i, 4),
particle_distance, rl)*
surface_frac(min(list_setup->cluster_size_j, 4),
particle_distance, rl);
drift *= nb_clust_frac_pairs_not_in_list_at_cutoff;
/* Convert the drift to drift per unit time per atom */
drift /= ir->nstlist*ir->delta_t*mtop->natoms;
if (debug)
{
fprintf(debug, "ib %3d %3d %3d rb %.3f %dx%d fac %.3f drift %.1e\n",
ib0, ib, ib1, rb,
list_setup->cluster_size_i, list_setup->cluster_size_j,
nb_clust_frac_pairs_not_in_list_at_cutoff,
drift);
}
if (fabs(drift) > ir->verletbuf_tol)
{
ib0 = ib;
}
else
{
ib1 = ib;
}
}
sfree(att);
*rlist = max(ir->rvdw, ir->rcoulomb) + ib1*resolution;
}
/* Try to increase nstlist when using the Verlet cut-off scheme */
static void increase_nstlist(FILE *fp, t_commrec *cr,
t_inputrec *ir, int nstlist_cmdline,
const gmx_mtop_t *mtop, matrix box,
gmx_bool bGPU)
{
float listfac_ok, listfac_max;
int nstlist_orig, nstlist_prev;
verletbuf_list_setup_t ls;
real rlistWithReferenceNstlist, rlist_inc, rlist_ok, rlist_max;
real rlist_new, rlist_prev;
size_t nstlist_ind = 0;
t_state state_tmp;
gmx_bool bBox, bDD, bCont;
const char *nstl_gpu = "\nFor optimal performance with a GPU nstlist (now %d) should be larger.\nThe optimum depends on your CPU and GPU resources.\nYou might want to try several nstlist values.\n";
const char *nve_err = "Can not increase nstlist because an NVE ensemble is used";
const char *vbd_err = "Can not increase nstlist because verlet-buffer-tolerance is not set or used";
const char *box_err = "Can not increase nstlist because the box is too small";
const char *dd_err = "Can not increase nstlist because of domain decomposition limitations";
char buf[STRLEN];
const float oneThird = 1.0f / 3.0f;
if (nstlist_cmdline <= 0)
{
if (ir->nstlist == 1)
{
/* The user probably set nstlist=1 for a reason,
* don't mess with the settings.
*/
return;
}
if (fp != NULL && bGPU && ir->nstlist < nstlist_try[0])
{
fprintf(fp, nstl_gpu, ir->nstlist);
}
nstlist_ind = 0;
while (nstlist_ind < NNSTL && ir->nstlist >= nstlist_try[nstlist_ind])
{
nstlist_ind++;
}
if (nstlist_ind == NNSTL)
{
/* There are no larger nstlist value to try */
return;
}
}
if (EI_MD(ir->eI) && ir->etc == etcNO)
{
if (MASTER(cr))
{
fprintf(stderr, "%s\n", nve_err);
}
if (fp != NULL)
{
fprintf(fp, "%s\n", nve_err);
}
return;
}
if (ir->verletbuf_tol == 0 && bGPU)
{
gmx_fatal(FARGS, "You are using an old tpr file with a GPU, please generate a new tpr file with an up to date version of grompp");
}
if (ir->verletbuf_tol < 0)
{
if (MASTER(cr))
{
fprintf(stderr, "%s\n", vbd_err);
}
if (fp != NULL)
{
fprintf(fp, "%s\n", vbd_err);
}
return;
}
if (bGPU)
{
listfac_ok = nbnxn_gpu_listfac_ok;
listfac_max = nbnxn_gpu_listfac_max;
}
else
{
listfac_ok = nbnxn_cpu_listfac_ok;
listfac_max = nbnxn_cpu_listfac_max;
}
nstlist_orig = ir->nstlist;
if (nstlist_cmdline > 0)
{
if (fp)
{
sprintf(buf, "Getting nstlist=%d from command line option",
nstlist_cmdline);
}
ir->nstlist = nstlist_cmdline;
}
verletbuf_get_list_setup(TRUE, bGPU, &ls);
/* Allow rlist to make the list a given factor larger than the list
* would be with the reference value for nstlist (10).
*/
nstlist_prev = ir->nstlist;
ir->nstlist = nbnxnReferenceNstlist;
calc_verlet_buffer_size(mtop, det(box), ir, -1, &ls, NULL,
&rlistWithReferenceNstlist);
ir->nstlist = nstlist_prev;
/* Determine the pair list size increase due to zero interactions */
rlist_inc = nbnxn_get_rlist_effective_inc(ls.cluster_size_j,
mtop->natoms/det(box));
rlist_ok = (rlistWithReferenceNstlist + rlist_inc)*pow(listfac_ok, oneThird) - rlist_inc;
rlist_max = (rlistWithReferenceNstlist + rlist_inc)*pow(listfac_max, oneThird) - rlist_inc;
if (debug)
{
fprintf(debug, "nstlist tuning: rlist_inc %.3f rlist_ok %.3f rlist_max %.3f\n",
rlist_inc, rlist_ok, rlist_max);
}
nstlist_prev = nstlist_orig;
rlist_prev = ir->rlist;
do
{
if (nstlist_cmdline <= 0)
{
ir->nstlist = nstlist_try[nstlist_ind];
}
/* Set the pair-list buffer size in ir */
calc_verlet_buffer_size(mtop, det(box), ir, -1, &ls, NULL, &rlist_new);
/* Does rlist fit in the box? */
bBox = (sqr(rlist_new) < max_cutoff2(ir->ePBC, box));
bDD = TRUE;
if (bBox && DOMAINDECOMP(cr))
{
/* Check if rlist fits in the domain decomposition */
if (inputrec2nboundeddim(ir) < DIM)
{
gmx_incons("Changing nstlist with domain decomposition and unbounded dimensions is not implemented yet");
}
copy_mat(box, state_tmp.box);
bDD = change_dd_cutoff(cr, &state_tmp, ir, rlist_new);
}
if (debug)
{
fprintf(debug, "nstlist %d rlist %.3f bBox %d bDD %d\n",
ir->nstlist, rlist_new, bBox, bDD);
}
bCont = FALSE;
if (nstlist_cmdline <= 0)
{
if (bBox && bDD && rlist_new <= rlist_max)
{
/* Increase nstlist */
nstlist_prev = ir->nstlist;
rlist_prev = rlist_new;
bCont = (nstlist_ind+1 < NNSTL && rlist_new < rlist_ok);
}
else
{
/* Stick with the previous nstlist */
ir->nstlist = nstlist_prev;
rlist_new = rlist_prev;
bBox = TRUE;
bDD = TRUE;
}
}
nstlist_ind++;
}
while (bCont);
if (!bBox || !bDD)
{
gmx_warning(!bBox ? box_err : dd_err);
if (fp != NULL)
{
fprintf(fp, "\n%s\n", bBox ? box_err : dd_err);
}
ir->nstlist = nstlist_orig;
}
else if (ir->nstlist != nstlist_orig || rlist_new != ir->rlist)
{
sprintf(buf, "Changing nstlist from %d to %d, rlist from %g to %g",
nstlist_orig, ir->nstlist,
ir->rlist, rlist_new);
if (MASTER(cr))
{
fprintf(stderr, "%s\n\n", buf);
}
if (fp != NULL)
{
fprintf(fp, "%s\n\n", buf);
}
ir->rlist = rlist_new;
ir->rlistlong = rlist_new;
}
}