//

// metropolis.c

//

//

// Created by Wu Chia Sheng on 21/4/14.

//

//

//particle is initialized such that the distance is greater than 1 hence attractive energy, relative fast to find lesser energy

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <mpi.h>

#include <time.h>

#define N 32

typedef struct {

double x;

double y;

double z;

}particle;

void createParticles(particle p[N]){

int i;

/* initialize random seed: */

srand (time(NULL));

for(i=0;i<N;i++){

p[i].x=(rand() % 100 + 1)/10.00;

p[i].y=(rand() % 100 + 1)/10.00;

p[i].z=(rand() % 100 + 1)/10.00;

}

}

int main(int argc, char** argv){

int i,j,k,l;

int timeStep=0;

int worldRank;

int worldSize;

double elapseTime;

clock_t start;

clock_t end;

float seconds1=0.00;

float seconds3=0.00;

int numParticle;

int dispParticle;

double distance;

double initialEnergy;

double energy;

double totalEnergy=0.00;

double localEnergy=0.00;

double globalEnergy;

double previousEnergy=0.00;

double fabGlobal;

double fabPrev;

particle p[N];

particle oldP[N];

int newX,newY,newZ;

//496 is derived from 32P2/2

int index1Pair[496];

int index2Pair[496];

MPI_Datatype particleType;

MPI_Datatype type[3]={MPI_DOUBLE,MPI_DOUBLE,MPI_DOUBLE};

int blocklen[3]={1,1,1};

MPI_Aint disp[3];

MPI_Aint extent;

//Initialize MPI

MPI_Init(&argc,&argv);

MPI_Comm_rank(MPI_COMM_WORLD,&worldRank);

MPI_Comm_size(MPI_COMM_WORLD,&worldSize);

MPI_Type_extent(MPI_DOUBLE,&extent);

disp[0]=0;

disp[1]=1*extent;

disp[2]=2*extent;

MPI_Type_struct(3,blocklen,disp,type,&particleType);

MPI_Type_commit(&particleType);

if(worldRank==0){

createParticles(p);

for(i=0;i<N;i++)

{

printf("Particle %d: X:%f,Y:%f,Z:%f\n",i,p[i].x,p[i].y,p[i].z);

}

}

while(1){

totalEnergy=0.00;

localEnergy=0.00;

globalEnergy=0.00;

//broadcast particle coordinates to all processors

MPI_Bcast(p,N,particleType, 0, MPI_COMM_WORLD);

/*assign number of particle to compute

particle decomposition technique is used

*/

numParticle =31;

dispParticle = worldRank*(numParticle);

//calculate total energy

//form array 1 that contains the index of first particle of a pair

l=0;

k=N-1;//-1 to exclude same index pair

for(i=0;i<N-1;i++){

for(j=0;j<k;j++){

index1Pair[l]=(N-1)-k+1;

l++;

}

k--;

}

//form array 2 that contains the index of second particle of a pair

l=0;

k=N-1;

for(i=0;i<N-1;i++){

for(j=0;j<k;j++){

index2Pair[l]=(N-1)-k+2+j;

l++;

}

k--;

}

for(i=0;i<numParticle;i++){

k=i+dispParticle;

distance = sqrt(pow(p[index1Pair[k]].x-p[index2Pair[k]].x,2.0)+pow(p[index1Pair[k]].y-p[index2Pair[k]].y,2.0)+pow(p[index1Pair[k]].z-p[index2Pair[k]].z,2.0));

if(distance == 0){

energy=0.00;

}

else

energy = 1/pow(distance,12.0)-1/pow(distance,6.0);

totalEnergy = totalEnergy + energy;

}

localEnergy = totalEnergy;

//sum of all energy

MPI_Allreduce(&localEnergy,&globalEnergy, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);

if(timeStep ==0){

initialEnergy=globalEnergy;

}

if(timeStep ==0 && worldRank==0)

printf("Initial Energy= %f\n",initialEnergy);

if(timeStep ==0){

initialEnergy=fabs(globalEnergy);

}

//accept new coordinate if new state energy less than previous state

fabGlobal = fabs(globalEnergy);

fabPrev = fabs(previousEnergy);

if( fabGlobal < fabPrev || timeStep==50000){

if(fabGlobal <= (initialEnergy/4.00) && timeStep!=0 || timeStep ==50000){

if(worldRank==0){

printf("Solution is found after %d\n",timeStep);

printf("New Energy = %f\n",globalEnergy);

}

break;

}

}

else if(timeStep!=0){

//if(worldRank==0)

//printf("greater");

for(i=0;i<N;i++){

p[i].x=oldP[i].x;

p[i].y=oldP[i].y;

p[i].z=oldP[i].z;

}

}

previousEnergy = globalEnergy;

//save old coordinates before moving particles

for(i=0;i<N;i++){

oldP[i].x=p[i].x;

oldP[i].y=p[i].y;

oldP[i].z=p[i].z;

}

/*

MOVING PARTICLES

*/

if(worldRank==0){

srand (time(NULL));

for(i=0;i<N;i++){

int randX=rand() % 19 + (-9);

int randY=rand() % 19 + (-9);

int randZ=rand() % 19 + (-9);

newX = p[i].x*100 + randX*1;

newY = p[i].y*100 + randY*1;

newZ = p[i].z*100 + randZ*1;

if(newX<=900 && newX>=100)

p[i].x = (double)newX/100;

if(newY<=900 && newY>=100)

p[i].y = (double)newY/100;

if(newZ<=900 && newZ>=100)

p[i].z = (double)newZ/100;

}

}

timeStep++;

}

MPI_Finalize();

return 0;

}