1 /* ----------------------------------------------------------------------
2 LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
3 https://www.lammps.org/
4 Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
5
6 Copyright (2003) Sandia Corporation. Under the terms of Contract
7 DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
8 certain rights in this software. This software is distributed under
9 the GNU General Public License.
10
11 See the README file in the top-level LAMMPS directory.
12 ------------------------------------------------------------------------- */
13
14 // c++_driver = simple example of how an umbrella program
15 // can invoke LAMMPS as a library on some subset of procs
16 // Syntax: simpleCC P in.lammps
17 // P = # of procs to run LAMMPS on
18 // must be <= # of procs the driver code itself runs on
19 // in.lammps = LAMMPS input script
20 // See README for compilation instructions
21
22 #include <cstdio>
23 #include <cstdlib>
24 #include <cstring>
25 #include <mpi.h>
26
27 // these are LAMMPS include files
28 #include "lammps.h"
29 #include "input.h"
30 #include "atom.h"
31 #include "library.h"
32
33 using namespace LAMMPS_NS;
34
main(int narg,char ** arg)35 int main(int narg, char **arg)
36 {
37 // setup MPI and various communicators
38 // driver runs on all procs in MPI_COMM_WORLD
39 // comm_lammps only has 1st P procs (could be all or any subset)
40
41 MPI_Init(&narg,&arg);
42
43 if (narg != 3) {
44 printf("Syntax: simpleCC P in.lammps\n");
45 exit(1);
46 }
47
48 int me,nprocs;
49 MPI_Comm_rank(MPI_COMM_WORLD,&me);
50 MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
51
52 int nprocs_lammps = atoi(arg[1]);
53 if (nprocs_lammps > nprocs) {
54 if (me == 0)
55 printf("ERROR: LAMMPS cannot use more procs than available\n");
56 MPI_Abort(MPI_COMM_WORLD,1);
57 }
58
59 int lammps;
60 if (me < nprocs_lammps) lammps = 1;
61 else lammps = MPI_UNDEFINED;
62 MPI_Comm comm_lammps;
63 MPI_Comm_split(MPI_COMM_WORLD,lammps,0,&comm_lammps);
64
65 // open LAMMPS input script
66
67 FILE *fp;
68 if (me == 0) {
69 fp = fopen(arg[2],"r");
70 if (fp == NULL) {
71 printf("ERROR: Could not open LAMMPS input script\n");
72 MPI_Abort(MPI_COMM_WORLD,1);
73 }
74 }
75
76 // run the input script thru LAMMPS one line at a time until end-of-file
77 // driver proc 0 reads a line, Bcasts it to all procs
78 // (could just send it to proc 0 of comm_lammps and let it Bcast)
79 // all LAMMPS procs call input->one() on the line
80
81 LAMMPS *lmp = NULL;
82 if (lammps == 1) lmp = new LAMMPS(0,NULL,comm_lammps);
83
84 int n;
85 char line[1024];
86 while (1) {
87 if (me == 0) {
88 if (fgets(line,1024,fp) == NULL) n = 0;
89 else n = strlen(line) + 1;
90 if (n == 0) fclose(fp);
91 }
92 MPI_Bcast(&n,1,MPI_INT,0,MPI_COMM_WORLD);
93 if (n == 0) break;
94 MPI_Bcast(line,n,MPI_CHAR,0,MPI_COMM_WORLD);
95 if (lammps == 1) lammps_command(lmp,line);
96 }
97
98 // run 10 more steps
99 // get coords from LAMMPS
100 // change coords of 1st atom
101 // put coords back into LAMMPS
102 // run a single step with changed coords
103
104 double *x = NULL;
105 double *v = NULL;
106
107 if (lammps == 1) {
108 lmp->input->one("run 10");
109
110 int natoms = static_cast<int> (lmp->atom->natoms);
111 x = new double[3*natoms];
112 v = new double[3*natoms];
113 lammps_gather_atoms(lmp,(char *) "x",1,3,x);
114 lammps_gather_atoms(lmp,(char *) "v",1,3,v);
115 double epsilon = 0.1;
116 x[0] += epsilon;
117 lammps_scatter_atoms(lmp,(char *) "x",1,3,x);
118
119 // these 2 lines are the same
120
121 // lammps_command(lmp,"run 1");
122 lmp->input->one("run 1");
123 }
124
125 // extract force on single atom two different ways
126
127 if (lammps == 1) {
128 double **f = (double **) lammps_extract_atom(lmp,(char *) "f");
129 printf("Force on 1 atom via extract_atom: %g\n",f[0][0]);
130
131 double *fx = (double *)
132 lammps_extract_variable(lmp,(char *) "fx",(char *) "all");
133 printf("Force on 1 atom via extract_variable: %g\n",fx[0]);
134 }
135
136 // use commands_string() and commands_list() to invoke more commands
137
138 const char *strtwo = (char *) "run 10\nrun 20";
139 if (lammps == 1) lammps_commands_string(lmp,strtwo);
140
141 const char *cmds[2];
142 cmds[0] = (char *) "run 10";
143 cmds[1] = (char *) "run 20";
144 if (lammps == 1) lammps_commands_list(lmp,2,cmds);
145
146 // delete all atoms
147 // create_atoms() to create new ones with old coords, vels
148 // initial thermo should be same as step 20
149
150 int *type = NULL;
151
152 if (lammps == 1) {
153 int natoms = static_cast<int> (lmp->atom->natoms);
154 type = new int[natoms];
155 for (int i = 0; i < natoms; i++) type[i] = 1;
156
157 lmp->input->one("delete_atoms group all");
158 lammps_create_atoms(lmp,natoms,NULL,type,x,v,NULL,0);
159 lmp->input->one("run 10");
160 }
161
162 delete [] x;
163 delete [] v;
164 delete [] type;
165
166 // close down LAMMPS
167
168 delete lmp;
169
170 // close down MPI
171
172 if (lammps == 1) MPI_Comm_free(&comm_lammps);
173 MPI_Barrier(MPI_COMM_WORLD);
174 MPI_Finalize();
175 }
176