/*
MPI Triad Census
by Kris Schnee

First attempt at a program that performs a basic type of triad census.
Meant for Steam user data, involving undirected graphs of low degree.

Strategy:
-Load the "egonet" data into structs that each list a certain node and its neighbors.
-Divide up the egonet data and assign to some processes.
	-Each process P gets put in charge of some set of nodes "this_process_nodes".
-For each process P:
	-For each node this_node in this_process_nodes:
		-Let "groups_to_examine" := []
		-For each neighbor in this_node's neighbors:
			-Let A = this_node
			-Let B = neighbor
			-For every other node C in the range (0,highest_node):
				groups_to_examine += (A,B,C)
[(0,3,4),(0,3,5),(0,3,6)...(0,7,1),(0,7,2)...]
		For each group in groups_to_examine:
			links = 1 ## We know AB exists.
			Examine AC, then BC.

			
THEIR VERSION

	For A in list of nodes w/neighbors:
		For B in neighbors of A with < number:
			Find # of single-edge triads AB is involved in, which is (N- (union of neighbors of A&B) )

	For A in entire list of nodes in the graph, that DO have neighbors listed:
		For B in "neighbors of A that have a smaller # than A":
			For C in "the union of all neighbors of A and of B":
(13,0,5)


*/

#include <stdio.h>
#include "mpi.h"

int main(int n_args, char** args)
{	
	// Invoke MPI for the hell of it. Not really using it yet.
	MPI_Init(&n_args, &args);
	
	printf("\n\n*** Demo of file I/O ***\n\n");
	
	// Open a file for reading text.
	FILE* input_file = fopen("input.txt","rt");
	if(input_file == NULL)
	{
		printf("Error: Couldn't find/open input file \"input.txt\". Create one, if not!\n");
		return(1);
	}
	
	printf("Got the file open successfully. Now trying to read and display it line by line.\n");
	
	char line[80]; // Stores up to 80 characters of text from one line of the file. Should be safe from buffer overflow hacks due to the way it's being used.
	while(fgets(line, 80, input_file) != NULL ) // Try to read a line, ending on a failure.
	{
		printf(line); // Since lines end with \n characters, a newline gets printed automatically.
	}

	// Note: To convert a string to an int:
	// int x;
	// sscanf(input_string,"%d",&x);
	
	fclose(input_file);
	
	printf("Now trying to write an output file.\n");
	
	// Open an output file for writing.
	FILE* output_file = fopen("output.txt","w"); // Note: overwrites old content, which is what we want.
	if(output_file == NULL)
	{
		printf("Error: Couldn't open output file.\n");
		return(1);
	}
	
	// Write some junk.
	int i;
	for(i=0;i<10;i++)
	{
		fputs("Some text\n",output_file);
	}
	fclose(output_file);
	
	printf("Success.");
	return 0;
}