move precomputation for factor_sqrt to individual Pair::compute() functions

the special_lj values may be changed for individual hybrid sub-styles
with pair_modify pair special. thus the factor_sqrt[] array may have
incorrect values when computed during Pair::init_style().

src/DPD-BASIC/pair_dpd.cpp

@@ -74,6 +74,10 @@ void PairDPD::compute(int eflag, int vflag)
   evdwl = 0.0;
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   double **x = atom->x;
   double **v = atom->v;
   double **f = atom->f;
@@ -266,10 +270,6 @@ void PairDPD::init_style()
     error->warning(FLERR, "Pair dpd needs newton pair on for momentum conservation");
 
   neighbor->add_request(this);
-
-  // precompute random force scaling factors
-
-  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
 }
 
 /* ----------------------------------------------------------------------

src/DPD-BASIC/pair_dpd_coul_slater_long.cpp

@@ -90,6 +90,10 @@ void PairDPDCoulSlaterLong::compute(int eflag, int vflag)
   evdwl = ecoul = 0.0;
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   double **x = atom->x;
   double **v = atom->v;
   double **f = atom->f;
@@ -334,11 +338,6 @@ void PairDPDCoulSlaterLong::init_style()
 
   neighbor->add_request(this);
 
-  // precompute random force scaling factors
-
-  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
-
-
   // ensure use of KSpace long-range solver, set g_ewald
 
  if (force->kspace == nullptr)

src/DPD-BASIC/pair_dpd_ext.cpp

@@ -81,6 +81,10 @@ void PairDPDExt::compute(int eflag, int vflag)
   evdwl = 0.0;
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   double **x = atom->x;
   double **v = atom->v;
   double **f = atom->f;
@@ -325,10 +329,6 @@ void PairDPDExt::init_style()
     error->warning(FLERR, "Pair dpd needs newton pair on for momentum conservation");
 
   neighbor->add_request(this);
-
-  // precompute random force scaling factors
-
-  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
 }
 
 /* ----------------------------------------------------------------------

src/DPD-BASIC/pair_dpd_ext_tstat.cpp

@@ -54,6 +54,10 @@ void PairDPDExtTstat::compute(int eflag, int vflag)
 
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   // adjust sigma if target T is changing
 
   if (t_start != t_stop) {

src/DPD-BASIC/pair_dpd_tstat.cpp

@@ -48,6 +48,10 @@ void PairDPDTstat::compute(int eflag, int vflag)
 
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   // adjust sigma if target T is changing
 
   if (t_start != t_stop) {

src/OPENMP/pair_dpd_ext_omp.cpp

@@ -60,6 +60,10 @@ void PairDPDExtOMP::compute(int eflag, int vflag)
 {
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   const int nall = atom->nlocal + atom->nghost;
   const int inum = list->inum;
 

src/OPENMP/pair_dpd_ext_tstat_omp.cpp

@@ -60,6 +60,10 @@ void PairDPDExtTstatOMP::compute(int eflag, int vflag)
 {
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   const int nall = atom->nlocal + atom->nghost;
   const int inum = list->inum;
 

src/OPENMP/pair_dpd_omp.cpp

@@ -59,6 +59,10 @@ void PairDPDOMP::compute(int eflag, int vflag)
 {
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   const int nall = atom->nlocal + atom->nghost;
   const int inum = list->inum;
 

src/OPENMP/pair_dpd_tstat_omp.cpp

@@ -60,6 +60,10 @@ void PairDPDTstatOMP::compute(int eflag, int vflag)
 {
   ev_init(eflag,vflag);
 
+  // precompute random force scaling factors
+
+  for (int i = 0; i < 4; ++i) special_sqrt[i] = sqrt(force->special_lj[i]);
+
   const int nall = atom->nlocal + atom->nghost;
   const int inum = list->inum;