/*
 * The Game of Life
 *
 * a cell is born, if it has exactly three neighbours 
 * a cell dies of loneliness, if it has less than two neighbours 
 * a cell dies of overcrowding, if it has more than three neighbours 
 * a cell survives to the next generation, if it does not die of loneliness 
 * or overcrowding 
 *
 * In this version, a 2D array of ints is used.  A 1 cell is on, a 0 cell is off.
 * The game plays a number of steps (given by the input), printing to the screen each time.  'x' printed
 * means on, space means off.
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
typedef unsigned char cell_t; 

cell_t ** allocate_board (int size) {
	cell_t ** board = (cell_t **) malloc(sizeof(cell_t*)*size);
	int	i;
	for (i=0; i<size; i++)
		board[i] = (cell_t *) malloc(sizeof(cell_t)*size);
	return board;
}

void free_board (cell_t ** board, int size) {
        int     i;
        for (i=0; i<size; i++)
                free(board[i]);
	free(board);
}


/* return the number of on cells adjacent to the i,j cell */
int adjacent_to (cell_t ** board, int size, int i, int j) {
	int	k, l, count=0;
	
	int sk = (i>0) ? i-1 : i;
	int ek = (i+1 < size) ? i+1 : i;
	int sl = (j>0) ? j-1 : j;
        int el = (j+1 < size) ? j+1 : j;

	for (k=sk; k<=ek; k++)
		for (l=sl; l<=el; l++)
			count+=board[k][l];
	count-=board[i][j];
	
	return count;
}

/* print the life board */
void print (cell_t ** board, int size) {
	int	i, j;
	/* for each row */
	for (j=0; j<size; j++) {
		/* print each column position... */
		for (i=0; i<size; i++) 
			printf ("%c", board[i][j] ? 'x' : ' ');
		/* followed by a carriage return */
		printf ("\n");
	}
}

/* read a file into the life board */
void read_file (FILE * f, cell_t ** board, int size) {
	int	i, j;
	char	*s = (char *) malloc(size+10);
	char c;
	for (j=0; j<size; j++) {
		/* get a string */
		fgets (s, size+10,f);
		/* copy the string to the life board */
		for (i=0; i<size; i++)
		{
		 	//c=fgetc(f);
			//putchar(c);
			board[i][j] = s[i] == 'x';
		}
		//fscanf(f,"\n");
	}
}

int main (int argc, char** argv) {
	int size, steps, rank, threads, localInit, localEnd;
	MPI_Status status;
	FILE    *f;
	cell_t ** prev;
	cell_t ** next;
	cell_t ** tmp;
	f = stdin;
	MPI_Init( &argc, &argv );
	MPI_Comm_rank( MPI_COMM_WORLD , &rank );
	MPI_Comm_size( MPI_COMM_WORLD , &threads );
	fscanf(f,"%d %d", &size, &steps);
	MPI_Bcast( &size , 1 , MPI_INT , 0 , MPI_COMM_WORLD);
	*&next = allocate_board (size);
	*&prev = allocate_board (size);
	/* print (next,size); */
	if (rank==0){
		printf("size: %d, thread: %d\n", size, rank);
		printf("Cheguei aqui 1!! thread: %d\n", rank);
		/* *&prev = allocate_board (size); */
		read_file (f, prev,size);
		fclose(f);
		/* print (prev,size); */
		/* *&next = allocate_board (size); */
		#ifdef DEBUG
		printf("Initial \n");
		/* print(prev,size); */
		printf("----------\n");
		#endif
	
		for (int i=0; i<steps; i++) {
			/* play (prev,next,size); */

			/* for each cell, apply the rules of Life */
			for (int j = 1; j < threads; j++){
				printf("Cheguei aqui 3!!\n");
				MPI_Send( &next , size*size , MPI_UNSIGNED_CHAR , j , 1 , MPI_COMM_WORLD);
			}
			for (int j = 1; j < threads; j++){
				MPI_Recv( &next , size*size , MPI_UNSIGNED_CHAR , j, 1 , MPI_COMM_WORLD , &status);	
				printf("Cheguei aqui 4!! rank: %d\n", j);
			}
			        #ifdef DEBUG
			printf("%d ----------\n", i);
			/* print (next,size); */
			#endif
			tmp = next;
			next = prev;
			prev = tmp;
		}
	}else{
		/* print (next,size); */
		/* printf("size: %d, thread: %d\n", size, rank); */
		printf("Cheguei aqui 2!! thread: %d\n", rank);
		MPI_Recv( &next , size*size , MPI_UNSIGNED_CHAR , 0, 1 , MPI_COMM_WORLD , &status);	
		/* print (next,size); */
		/* printf("\n\nTESTE: %c\n\n", next[0][0]); */
		int chunk = size/(threads-2);
		printf("size: %d, threads: %d, chunk: %d\n" , size, threads, chunk);
		localInit = rank*chunk-chunk;
		localEnd = (rank+1)*chunk-chunk;
		if (rank==threads-1){
			localEnd = size;
		}
		for (int i=localInit; i<localEnd; i++){
			for (int j=0; j<size; j++) {
				/* printf("teste: %d\n\n" , next[0][0]); */
				printf("rank: %d, localInit: %d, localEnd: %d, i: %d, j: %d\n" , rank, localInit, localEnd, i, j);
				int a = adjacent_to (prev, size, i, j);
				if (a == 2) next[i][j] = prev[i][j];
				if (a == 3) next[i][j] = 1;
				if (a < 2) next[i][j] = 0;
				if (a > 3) next[i][j] = 0;
				printf("Cheguei aqui 5!!\n");
			}
		}
		MPI_Send( &next , size*size , MPI_UNSIGNED_CHAR , 0 , 1 , MPI_COMM_WORLD);
	}
	print (prev,size);
	free_board(prev,size);
	free_board(next,size);
	MPI_Finalize();
}
 

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}  

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition); 

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}