int main ()
/******************************************************************************/
/*
Purpose:
MAIN is the main program for MD_OPENMP.
Discussion:
MD implements a simple molecular dynamics simulation.
The program uses Open MP directives to allow parallel computation.
The velocity Verlet time integration scheme is used.
The particles interact with a central pair potential.
Output of the program is saved in the TNG format, which is why this
code is included in the TNG API release. The high-level API of the
TNG API is used where appropriate.
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
8 Jan 2013
Author:
Original FORTRAN77 version by Bill Magro.
C version by John Burkardt.
TNG trajectory output by Magnus Lundborg.
Parameters:
None
*/
{
float *acc;
float *box;
float *box_shape;
float dt = 0.0002;
float e0;
float *force;
int i;
float kinetic;
float mass = 1.0;
int nd = 3;
int np = 50;
float *pos;
float potential;
int proc_num;
int seed = 123456789;
int step;
int step_num = 50000;
int step_print;
int step_print_index;
int step_print_num;
int step_save;
float *vel;
float wtime;
tng_trajectory_t traj;
tng_molecule_t molecule;
tng_chain_t chain;
tng_residue_t residue;
tng_atom_t atom;
timestamp ( );
proc_num = omp_get_num_procs ( );
acc = ( float * ) malloc ( nd * np * sizeof ( float ) );
box = ( float * ) malloc ( nd * sizeof ( float ) );
box_shape = (float *) malloc (9 * sizeof (float));
force = ( float * ) malloc ( nd * np * sizeof ( float ) );
pos = ( float * ) malloc ( nd * np * sizeof ( float ) );
vel = ( float * ) malloc ( nd * np * sizeof ( float ) );
printf ( "\n" );
printf ( "MD_OPENMP\n" );
printf ( " C/OpenMP version\n" );
printf ( "\n" );
printf ( " A molecular dynamics program.\n" );
printf ( "\n" );
printf ( " NP, the number of particles in the simulation is %d\n", np );
printf ( " STEP_NUM, the number of time steps, is %d\n", step_num );
printf ( " DT, the size of each time step, is %f\n", dt );
printf ( "\n" );
printf ( " Number of processors available = %d\n", proc_num );
printf ( " Number of threads = %d\n", omp_get_max_threads ( ) );
printf("\n");
printf(" Initializing trajectory storage.\n");
/* Initialize the TNG trajectory */
tng_util_trajectory_open(TNG_EXAMPLE_FILES_DIR "tng_md_out.tng", 'w', &traj);
/* Set molecules data */
/* N.B. This is still not done using utility functions. The low-level API
* is used. */
printf(" Creating molecules in trajectory.\n");
tng_molecule_add(traj, "water", &molecule);
tng_molecule_chain_add(traj, molecule, "W", &chain);
tng_chain_residue_add(traj, chain, "WAT", &residue);
if(tng_residue_atom_add(traj, residue, "O", "O", &atom) == TNG_CRITICAL)
{
tng_util_trajectory_close(&traj);
printf(" Cannot create molecules.\n");
exit(1);
}
tng_molecule_cnt_set(traj, molecule, np);
/*
Set the dimensions of the box.
*/
for(i = 0; i < 9; i++)
{
box_shape[i] = 0.0;
}
for ( i = 0; i < nd; i++ )
{
box[i] = 10.0;
/* box_shape stores 9 values according to the TNG specs */
box_shape[i*nd + i] = box[i];
}
printf ( "\n" );
printf ( " Initializing positions, velocities, and accelerations.\n" );
/*
Set initial positions, velocities, and accelerations.
*/
initialize ( np, nd, box, &seed, pos, vel, acc );
/*
Compute the forces and energies.
*/
printf ( "\n" );
printf ( " Computing initial forces and energies.\n" );
compute ( np, nd, pos, vel, mass, force, &potential, &kinetic );
e0 = potential + kinetic;
/* Saving frequency */
step_save = 400;
step_print = 0;
step_print_index = 0;
step_print_num = 10;
/*
This is the main time stepping loop:
Compute forces and energies,
Update positions, velocities, accelerations.
*/
printf(" Every %d steps box shape, particle positions, velocities and forces are\n",
step_save);
printf(" saved to a TNG trajectory file.\n");
printf ( "\n" );
printf ( " At certain step intervals, we report the potential and kinetic energies.\n" );
printf ( " The sum of these energies should be a constant.\n" );
printf ( " As an accuracy check, we also print the relative error\n" );
printf ( " in the total energy.\n" );
printf ( "\n" );
printf ( " Step Potential Kinetic (P+K-E0)/E0\n" );
printf ( " Energy P Energy K Relative Energy Error\n" );
printf ( "\n" );
step = 0;
printf ( " %8d %14f %14f %14e\n",
step, potential, kinetic, ( potential + kinetic - e0 ) / e0 );
step_print_index++;
step_print = ( step_print_index * step_num ) / step_print_num;
/* Set the output frequency of box shape, positions, velocities and forces */
if(tng_util_box_shape_write_frequency_set(traj, step_save) != TNG_SUCCESS)
{
printf("Error setting writing frequency data. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
if(tng_util_pos_write_frequency_set(traj, step_save) != TNG_SUCCESS)
{
printf("Error setting writing frequency data. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
if(tng_util_vel_write_frequency_set(traj, step_save) != TNG_SUCCESS)
{
printf("Error setting writing frequency data. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
if(tng_util_force_write_frequency_set(traj, step_save) != TNG_SUCCESS)
{
printf("Error setting writing frequency data. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
/* Write the first frame of box shape, positions, velocities and forces */
if(tng_util_box_shape_write(traj, 0, box_shape) != TNG_SUCCESS)
{
printf("Error writing box shape. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
if(tng_util_pos_write(traj, 0, pos) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
exit(1);
}
if(tng_util_vel_write(traj, 0, vel) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
exit(1);
}
if(tng_util_force_write(traj, 0, force) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
exit(1);
}
wtime = omp_get_wtime ( );
for ( step = 1; step < step_num; step++ )
{
compute ( np, nd, pos, vel, mass, force, &potential, &kinetic );
if ( step == step_print )
{
printf ( " %8d %14f %14f %14e\n", step, potential, kinetic,
( potential + kinetic - e0 ) / e0 );
step_print_index++;
step_print = ( step_print_index * step_num ) / step_print_num;
}
if(step % step_save == 0)
{
/* Write box shape, positions, velocities and forces */
if(tng_util_box_shape_write(traj, step, box_shape) != TNG_SUCCESS)
{
printf("Error writing box shape. %s: %d\n",
__FILE__, __LINE__);
exit(1);
}
if(tng_util_pos_write(traj, step, pos) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
break;
}
if(tng_util_vel_write(traj, step, vel) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
break;
}
if(tng_util_force_write(traj, step, force) != TNG_SUCCESS)
{
printf("Error adding data. %s: %d\n", __FILE__, __LINE__);
break;
}
}
update ( np, nd, pos, vel, force, acc, mass, dt );
}
wtime = omp_get_wtime ( ) - wtime;
printf ( "\n" );
printf ( " Elapsed time for main computation:\n" );
printf ( " %f seconds.\n", wtime );
free ( acc );
free ( box );
free ( box_shape );
free ( force );
free ( pos );
free ( vel );
/* Close the TNG output. */
tng_util_trajectory_close(&traj);
printf ( "\n" );
printf ( "MD_OPENMP\n" );
printf ( " Normal end of execution.\n" );
printf ( "\n" );
timestamp ( );
return 0;
}
static int write_tng_timestep(void *v, const molfile_timestep_t *ts)
{
float box_shape[9];
tngdata *tng = (tngdata *)v;
double time;
/* If there are fewer particles in the TNG mol system (write_tng_structure
* has not already been performed) compensate by creating implicit particles,
* which will not have full atom information. */
tng_implicit_num_particles_set(tng->tng_traj, tng->natoms);
if(!ts)
{
return MOLFILE_ERROR;
}
time = ts->physical_time * PICO;
convert_vmd_box_shape_to_tng(ts, box_shape);
if(tng->step == 1 && ts->physical_time != 0)
{
tng->time_per_frame = time;
tng_time_per_frame_set(tng->tng_traj, tng->time_per_frame);
}
if(tng->time_per_frame < 0)
{
// fprintf(stderr, "tngplugin) Writing frame without time stamp\n");
tng_util_box_shape_write(tng->tng_traj, tng->step, box_shape);
tng_util_pos_write(tng->tng_traj, tng->step, ts->coords);
}
else
{
// fprintf(stderr, "tngplugin) Writing frame with time stamp\n");
tng_util_box_shape_with_time_write(tng->tng_traj, tng->step, time,
box_shape);
tng_util_pos_with_time_write(tng->tng_traj, tng->step, time,
ts->coords);
}
if(tng->step == 0)
{
tng_util_pos_write_interval_set(tng->tng_traj, 1);
tng_util_box_shape_write_interval_set(tng->tng_traj, 1);
}
if(ts->velocities)
{
fprintf(stderr, "tngplugin) Writing TNG velocities\n");
if(tng->time_per_frame < 0)
{
tng_util_vel_write(tng->tng_traj, tng->step, ts->velocities);
}
else
{
tng_util_vel_with_time_write(tng->tng_traj, tng->step, time,
ts->velocities);
}
if(tng->step == 0)
{
tng_util_vel_write_interval_set(tng->tng_traj, 1);
}
}
tng->step++;
return MOLFILE_SUCCESS;
}