#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <time.h>


/* ------------------------------------------------------
 * Data structure of a matrix
 -------------------------------------------------------- */

#define STR_ELEM "%lf "   /* String to read/write the item elem_t */
#define ELEMSEP "%lf, "   /* String to write the result elem_t */

typedef double elem_t;

typedef struct matrix_t {
	unsigned rows, cols;
	unsigned start;        /* Lower array bound */
	unsigned end;          /* Upper array row bound */
	elem_t **data;
	elem_t **_data;        /* Pointer to the mem block */
} matrix_t;


/* ------------------------------------------------------
 * Prints error messages
 -------------------------------------------------------- */

void error(char *msg)
{
	printf("Error: %s\n", msg);
	exit(1);
}


/* ------------------------------------------------------
 * Prints an error when there is not enough memory to
 * allocate a matrix
 -------------------------------------------------------- */

void error_not_enough_memory(void)
{
	error("There is not enough memory to allocate a matrix");
}


/* ------------------------------------------------------
 * Allocates memory for "rows" pointers.
 * Then memory for "cols" numbers are allocated for rows
 * between "start" and "end"
 * Other rows aren't allocated
 -------------------------------------------------------- */

matrix_t *matrix_alloc(unsigned rows, unsigned cols, unsigned start, unsigned end)
{
	matrix_t *result = malloc(sizeof(matrix_t));
	unsigned row;

	if (!result)
		error_not_enough_memory();

	result->rows = rows;
	result->cols = cols;
	result->start = start;
	result->end = end;

	result->_data = malloc(rows * sizeof(elem_t *));
	if (!result->_data)
		error_not_enough_memory();

	result->data = result->_data - start;

	for (row = start; row < end; row++) {
		result->data[row] = malloc(sizeof(elem_t) * cols);
		if (!result->data[row])
			error_not_enough_memory();
	}

  return result;
}


/* ------------------------------------------------------
 * Reads a chunk of a matrix from file
   ------------------------------------------------------ */
matrix_t *matrix_read_chunk(char *fname, unsigned id, unsigned N)
{
	unsigned start, end, chunk_size;
	unsigned rows, cols, row, col;
  unsigned div, rest;
	matrix_t *r;
	elem_t dummy;

	FILE *f = fopen(fname, "rt");
	if (!f) {
		printf("No se pudo abrir fichero '%s\n'", fname);
		exit(1);
	}

	fscanf(f, "%u %u\n", &rows, &cols);

  div  = rows / N;
  rest = rows % N;

  if (id < rest) {
    chunk_size = div + 1;
    start = id * chunk_size;
  }
  else {
    chunk_size = div;
    start = id * chunk_size + rest;
  }

  end = start + chunk_size;

	r = matrix_alloc(chunk_size, cols, start, end);

	for (row = 0; row < start; row++)
		for (col = 0; col < cols; col++) {
			fscanf(f, STR_ELEM, &dummy);
		}

	for (; row < end; row++)
		for (col = 0; col < cols; col++) {
			fscanf(f, STR_ELEM, &(r->data[row][col]));
		}

	fclose(f);

	return r;
}


/* ------------------------------------------------------
 * Reads a matrix from file
 -------------------------------------------------------- */
matrix_t *matrix_read(char *fname)
{
	return matrix_read_chunk(fname, 0, 1);
}


/* ------------------------------------------------------
 * Reads a matrix from STDOUT 
 * ------------------------------------------------------ */

matrix_t *matrix_read_stdout()
{
	unsigned rows, cols, r, c;
	matrix_t *m;

	scanf("%u %u", &rows, &cols);

	m = matrix_alloc(rows, cols, 0, rows);

	for (r = 0; r < rows; r++) 
		for (c = 0; c < cols; c++) {
			scanf(STR_ELEM, &(m->data[r][c]));
		}
  return m;
}


/* ------------------------------------------------------
 * Prints the content of a matrix, in a Perl format
 -------------------------------------------------------- */

void matrix_print(matrix_t *m)
{
	unsigned row, col;

	if (!m) return;

  printf("[ ");
	for (row = m->start; row < m->end; row++) {
    printf("[ ");
		for (col = 0; col < m->cols; col++) {
		  printf(ELEMSEP, m->data[row][col]);
    }
    printf("],\n");
  }
  printf("]\n");
}


/* ------------------------------------------------------
 * Returns the scalar product between the row "row_m1" of
 * the matrix "m1" and the column "col_m2" of the matrix
 * "m2"
 -------------------------------------------------------- */

elem_t p_escalar(matrix_t *m1, matrix_t *m2, unsigned row_m1, unsigned col_m2)
{
	unsigned i;
	elem_t result = 0;

	for (i = 0; i < m1->cols; i++)
		result += m1->data[row_m1][i] * m2->data[i][col_m2];

	return result;
}


/* ------------------------------------------------------
 * Returns the product between the matrix "m1" and the
 * matrix "m2"
   ------------------------------------------------------ */

matrix_t *matrix_mult(matrix_t *m1, matrix_t *m2)
{
	matrix_t *r = NULL;
	unsigned rows, cols;
	unsigned row, col;

	if (!m1 || !m2)
		error("One of the matrix is null");

	rows = m1->end - m1->start;
	cols = m2->cols;

	r = matrix_alloc(rows, cols, m1->start, m1->end);
	
	for (row = m1->start; row < m1->end; row++)
		for (col = 0; col < cols; col++)
			r->data[row][col] = p_escalar(m1, m2, row, col);

	return r;
}


/* ------------------------------------------------------
 * Main program
 -------------------------------------------------------- */

int main(int argc, char *argv[])
{
  matrix_t *m1, *m2, *m3;
  struct timeval ini, end;
  double t1, t2;
  unsigned id, N;

  if (argc != 5) {
    printf("Parameters: matrix <id> <N> <file m1> <file m2>\n");
    printf("Con:\n");
    printf("\t<id> Number of process (0..N-1)\n");
    printf("\t<N> Total number of processes\n");
    printf("\t<file m1> Matrix A\n");
    printf("\t<file m2> Matrix B\n");
    exit(2);
  }

  id = atoi(argv[1]);
  N = atoi(argv[2]);

  m1 = matrix_read_chunk(argv[3], id, N);
  m2 = matrix_read(argv[4]);
  
  //gettimeofday(&ini, NULL);
  m3 = matrix_mult(m1, m2);
  //gettimeofday(&end, NULL);

  //t1 = ini.tv_sec+(ini.tv_usec/1000000.0);
  //t2 = end.tv_sec+(end.tv_usec/1000000.0);
  //printf("Elapsed Time: %.6lf seconds\n", (t2 - t1));

  matrix_print(m3);

  return EXIT_SUCCESS;
}