// Michael Chen, 11.1.2007
// Wind velocity problem
#include <stdio.h>
#include <math.h>
#include "mpi.h"
//defines important variables
const double theta = 45;
const double v0 = 134.11200;
const double rf= 0.0034;
const double dt = 0.01;
const double pi = 3.1415926;
const double g = 9.80665;
double ax;
double ay;

int main(int argc, char* argv[])
{
	int					rank,size;
	MPI_Status				status;
	int					k,tag=0;
	double					y;
	//initializes MPI
	MPI_Init(&argc,&argv);
	MPI_Comm_size(MPI_COMM_WORLD,&size);
	MPI_Comm_rank(MPI_COMM_WORLD,&rank);
		
	double angle;
	double maxangle=90.0;
	double wvel;	
	double wmax=50.0;
	int flag=0;
	//args is the array passed from master-slave and vice-versa
	double args[3];	
	if(rank==0)            // parent process
	{	
		k=1;
		//k is the processor the parent process passes to
		flag=1;
		//values from angle 0 to 50 and wind velocity from -50 to 50
		for(angle=0.0;angle<=maxangle;angle+=0.5)
			for (wvel=-50.0;wvel<=wmax;wvel+=0.1)			
			{
				//if all child processes are busy, wait to receive info
				if (flag>=size)
				{
					MPI_Recv(args,3,MPI_DOUBLE,k,tag,MPI_COMM_WORLD,&status);
					printf("receiving! endx:%3.2f\n", args[2]);					
					flag--;				
				}
				//after receiving, send info to the same process	
					args[0]=wvel;
					args[1]=angle;
					args[2]=1337.0;
					MPI_Send(args,3,MPI_DOUBLE,k,tag,MPI_COMM_WORLD);
				//move to the next process and go around the for loop
					k++;
					flag++;										
					if (k>=size)
						k=1;
				//making sure not to exceed number of computers available
					printf("sending! angle:%3.2f,wvel:%3.2f\n",angle,wvel);	
			}
		//this section of code makes sure that all values have been received	
		int recall=0;		
		int ori=k-1;
		if (ori<1)
			ori=size;
		//printf("here?\n");		
		while (recall==0)
		{
			if (size==2)
				{
				MPI_Recv(args,3,MPI_DOUBLE,k,tag,MPI_COMM_WORLD,&status);
				printf("%3.2f\n",args[2]);				
				break;
				}
			MPI_Recv(args,3,MPI_DOUBLE,k,tag,MPI_COMM_WORLD,&status);
			printf("%3.2f\n",args[2]);			
			k++;			
			if (k>=size)
				k=1;
			if (k==ori)
				recall=1;								
		}
		//this portion of code ends all child processes
		args[0]=0.0;
		args[1]=0.0;
		args[2]=666.0;
		int n;
		for (n=1;n<size;n++)
			MPI_Send(args,3,MPI_DOUBLE,n,tag,MPI_COMM_WORLD);					
			
				
	}
	else                   // child process
	{
		while(1)
		{
			double px = 0;
			double py = 0;
			//receives info and sets initial velocity
			MPI_Recv(args,3,MPI_DOUBLE,0,tag,MPI_COMM_WORLD,&status);			
			double vx = v0*cos(args[1]*M_PI/180);
			double vy = v0*sin(args[1]*M_PI/180);
			double vw = -args[0];
			//checks to see if parent process ends this process
			if (args[2]==666.0)
				break;
			while (py>=0) //as long as the projectile has height
			{
				//recalculates acceleration and accounts for it
				ax = (vx-vw)*(vx-vw)*rf;
				//acceleration of wind depends on direction of wind
				//with respect to the direction of the projectile
				if (vw<vx)
					ax=-ax;
				//checks if wind velocity is working with/against gravity
				if (vy>0.0)
					ay=-g-rf*vy*vy;
				else 
					ay=-g+rf*vy*vy;
				vx+=(ax*dt);
				vy+=(ay*dt);
				px+=vx;
				py+=vy;
			}
			//sets value as the ending location of projectile and sends it
			args[2]=px;
			MPI_Send(args,3,MPI_DOUBLE,0,tag,MPI_COMM_WORLD);
		}
	}
	//finishes MPI
	MPI_Finalize();

	return 0;
}