#ifdef TNG_BUILD_OPENMP_EXAMPLES #include "tng/tng_io.h" #include #include #include #include #include int main (); void compute ( int np, int nd, float pos[], float vel[], float mass, float f[], float *pot, float *kin ); float dist ( int nd, float r1[], float r2[], float dr[] ); void initialize ( int np, int nd, float box[], int *seed, float pos[], float vel[], float acc[] ); float r8_uniform_01 ( int *seed ); void timestamp ( void ); void update ( int np, int nd, float pos[], float vel[], float f[], float acc[], float mass, float dt ); /******************************************************************************/ 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; } /******************************************************************************/ void compute ( int np, int nd, float pos[], float vel[], float mass, float f[], float *pot, float *kin ) /******************************************************************************/ /* Purpose: COMPUTE computes the forces and energies. Discussion: The computation of forces and energies is fully parallel. The potential function V(X) is a harmonic well which smoothly saturates to a maximum value at PI/2: v(x) = ( sin ( min ( x, PI2 ) ) )**2 The derivative of the potential is: dv(x) = 2.0 * sin ( min ( x, PI2 ) ) * cos ( min ( x, PI2 ) ) = sin ( 2.0 * min ( x, PI2 ) ) Licensing: This code is distributed under the GNU LGPL license. Modified: 21 November 2007 Author: Original FORTRAN77 version by Bill Magro. C version by John Burkardt. Parameters: Input, int NP, the number of particles. Input, int ND, the number of spatial dimensions. Input, float POS[ND*NP], the position of each particle. Input, float VEL[ND*NP], the velocity of each particle. Input, float MASS, the mass of each particle. Output, float F[ND*NP], the forces. Output, float *POT, the total potential energy. Output, float *KIN, the total kinetic energy. */ { float d; float d2; int i; int j; int k; float ke; float pe; float PI2 = 3.141592653589793 / 2.0; float rij[3]; pe = 0.0; ke = 0.0; # pragma omp parallel \ shared ( f, nd, np, pos, vel ) \ private ( i, j, k, rij, d, d2 ) # pragma omp for reduction ( + : pe, ke ) for ( k = 0; k < np; k++ ) { /* Compute the potential energy and forces. */ for ( i = 0; i < nd; i++ ) { f[i+k*nd] = 0.0; } for ( j = 0; j < np; j++ ) { if ( k != j ) { d = dist ( nd, pos+k*nd, pos+j*nd, rij ); /* Attribute half of the potential energy to particle J. */ if ( d < PI2 ) { d2 = d; } else { d2 = PI2; } pe = pe + 0.5 * pow ( sin ( d2 ), 2 ); for ( i = 0; i < nd; i++ ) { f[i+k*nd] = f[i+k*nd] - rij[i] * sin ( 2.0 * d2 ) / d; } } } /* Compute the kinetic energy. */ for ( i = 0; i < nd; i++ ) { ke = ke + vel[i+k*nd] * vel[i+k*nd]; } } ke = ke * 0.5 * mass; *pot = pe; *kin = ke; return; } /******************************************************************************/ float dist ( int nd, float r1[], float r2[], float dr[] ) /******************************************************************************/ /* Purpose: DIST computes the displacement (and its norm) between two particles. Licensing: This code is distributed under the GNU LGPL license. Modified: 21 November 2007 Author: Original FORTRAN77 version by Bill Magro. C version by John Burkardt. Parameters: Input, int ND, the number of spatial dimensions. Input, float R1[ND], R2[ND], the positions of the particles. Output, float DR[ND], the displacement vector. Output, float D, the Euclidean norm of the displacement. */ { float d; int i; d = 0.0; for ( i = 0; i < nd; i++ ) { dr[i] = r1[i] - r2[i]; d = d + dr[i] * dr[i]; } d = sqrt ( d ); return d; } /******************************************************************************/ void initialize ( int np, int nd, float box[], int *seed, float pos[], float vel[], float acc[] ) /******************************************************************************/ /* Purpose: INITIALIZE initializes the positions, velocities, and accelerations. Licensing: This code is distributed under the GNU LGPL license. Modified: 21 November 2007 Author: Original FORTRAN77 version by Bill Magro. C version by John Burkardt. Parameters: Input, int NP, the number of particles. Input, int ND, the number of spatial dimensions. Input, float BOX[ND], specifies the maximum position of particles in each dimension. Input, int *SEED, a seed for the random number generator. Output, float POS[ND*NP], the position of each particle. Output, float VEL[ND*NP], the velocity of each particle. Output, float ACC[ND*NP], the acceleration of each particle. */ { int i; int j; /* Give the particles random positions within the box. */ for ( i = 0; i < nd; i++ ) { for ( j = 0; j < np; j++ ) { pos[i+j*nd] = box[i] * r8_uniform_01 ( seed ); } } for ( j = 0; j < np; j++ ) { for ( i = 0; i < nd; i++ ) { vel[i+j*nd] = 0.0; } } for ( j = 0; j < np; j++ ) { for ( i = 0; i < nd; i++ ) { acc[i+j*nd] = 0.0; } } return; } /******************************************************************************/ float r8_uniform_01 ( int *seed ) /******************************************************************************/ /* Purpose: R8_UNIFORM_01 is a unit pseudorandom R8. Discussion: This routine implements the recursion seed = 16807 * seed mod ( 2**31 - 1 ) unif = seed / ( 2**31 - 1 ) The integer arithmetic never requires more than 32 bits, including a sign bit. Licensing: This code is distributed under the GNU LGPL license. Modified: 11 August 2004 Author: John Burkardt Reference: Paul Bratley, Bennett Fox, Linus Schrage, A Guide to Simulation, Springer Verlag, pages 201-202, 1983. Bennett Fox, Algorithm 647: Implementation and Relative Efficiency of Quasirandom Sequence Generators, ACM Transactions on Mathematical Software, Volume 12, Number 4, pages 362-376, 1986. Parameters: Input/output, int *SEED, a seed for the random number generator. Output, float R8_UNIFORM_01, a new pseudorandom variate, strictly between 0 and 1. */ { int k; float r; k = *seed / 127773; *seed = 16807 * ( *seed - k * 127773 ) - k * 2836; if ( *seed < 0 ) { *seed = *seed + 2147483647; } r = ( float ) ( *seed ) * 4.656612875E-10; return r; } /******************************************************************************/ void timestamp ( void ) /******************************************************************************/ /* Purpose: TIMESTAMP prints the current YMDHMS date as a time stamp. Example: 31 May 2001 09:45:54 AM Licensing: This code is distributed under the GNU LGPL license. Modified: 24 September 2003 Author: John Burkardt Parameters: None */ { # define TIME_SIZE 40 static char time_buffer[TIME_SIZE]; const struct tm *tm; time_t now; now = time ( NULL ); tm = localtime ( &now ); strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm ); printf ( "%s\n", time_buffer ); return; # undef TIME_SIZE } /******************************************************************************/ void update ( int np, int nd, float pos[], float vel[], float f[], float acc[], float mass, float dt ) /******************************************************************************/ /* Purpose: UPDATE updates positions, velocities and accelerations. Discussion: The time integration is fully parallel. A velocity Verlet algorithm is used for the updating. x(t+dt) = x(t) + v(t) * dt + 0.5 * a(t) * dt * dt v(t+dt) = v(t) + 0.5 * ( a(t) + a(t+dt) ) * dt a(t+dt) = f(t) / m Licensing: This code is distributed under the GNU LGPL license. Modified: 17 April 2009 Author: Original FORTRAN77 version by Bill Magro. C version by John Burkardt. Parameters: Input, int NP, the number of particles. Input, int ND, the number of spatial dimensions. Input/output, float POS[ND*NP], the position of each particle. Input/output, float VEL[ND*NP], the velocity of each particle. Input, float F[ND*NP], the force on each particle. Input/output, float ACC[ND*NP], the acceleration of each particle. Input, float MASS, the mass of each particle. Input, float DT, the time step. */ { int i; int j; float rmass; rmass = 1.0 / mass; # pragma omp parallel \ shared ( acc, dt, f, nd, np, pos, rmass, vel ) \ private ( i, j ) # pragma omp for for ( j = 0; j < np; j++ ) { for ( i = 0; i < nd; i++ ) { pos[i+j*nd] = pos[i+j*nd] + vel[i+j*nd] * dt + 0.5 * acc[i+j*nd] * dt * dt; vel[i+j*nd] = vel[i+j*nd] + 0.5 * dt * ( f[i+j*nd] * rmass + acc[i+j*nd] ); acc[i+j*nd] = f[i+j*nd] * rmass; } } return; } #endif