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Full Discussion: generate array of random numbers
Top Forums Programming generate array of random numbers Post 302595896 by saboture88 on Sunday 5th of February 2012 09:09:40 PM
Old 02-05-2012
generate array of random numbers
hi guys,
I am writing a c program that generates a two dimensional array to make matrix and a vector of random numbers and perform multiplication. I can't figure out whats wrong with my code. It generates a matrix of random numbers but all the numbers in the vector array is same and so is the result array. I don't see anything wrong with my multiplication algorithm but could anyone check it, please?

here is my code. help me figure out whats wrong with this
Code:
#include <iostream>
#include <cstdlib>
#include <time.h>

using namespace std;

const int mat_rows = 5;
const int mat_cols = 4;
const int vec_rows = mat_cols;
const int vec_cols = 0;

int matrix [mat_rows] [mat_cols];
int vector [vec_rows] [0];
int result [mat_rows] [0];
int res;

int main ()
{
srand (time(NULL));
/*Filling matrix with random value between 0 - 10 */
for (int i = 0; i < mat_rows; i++)
        for (int j = 0; j < mat_cols; j++)
                matrix [i][j] = rand () % 50;

/*Filling vector with random value between 0 - 10*/
for (int i = 0; i < vec_rows; i++)
        vector [i] [0]= rand () % 50;

cout << "Printing out the matrix" << "\n" << endl;
for (int i = 0; i < mat_rows; i++)
        {
        for (int j = 0; j < mat_cols; j++)
                cout << matrix [i][j] << "   ";
        cout << endl;
        }
cout << "Printing out the vector" << "\n" << endl;
for (int i = 0; i < vec_rows; i++)
        cout << vector [i] [0] << endl;

for (int i = 0; i < mat_rows; i++)
        {
        res = 0;
        int vrows = 0;
        for (int j = 0; j < mat_cols; j++)
                {
                res = res + ((matrix [i] [j]) * (vector [vrows] [0]));
                vrows++;
                }
        result [i] [0] = res;
        }

for (int i = 0; i < mat_rows; i++)
        cout << result [i] [0] << endl;

return 0;
}

thanks
 

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LEARN ABOUT OSX

sranddev

RAND(3) 						   BSD Library Functions Manual 						   RAND(3)

NAME

     rand, rand_r, srand, sranddev -- bad random number generator

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <stdlib.h>

     int
     rand(void);

     int
     rand_r(unsigned *seed);

     void
     srand(unsigned seed);

     void
     sranddev(void);

DESCRIPTION

     These interfaces are obsoleted by random(3).

     The rand() function computes a sequence of pseudo-random integers in the range of 0 to RAND_MAX (as defined by the header file <stdlib.h>).

     The srand() function sets its argument seed as the seed for a new sequence of pseudo-random numbers to be returned by rand().  These
     sequences are repeatable by calling srand() with the same seed value.

     If no seed value is provided, the functions are automatically seeded with a value of 1.

     The sranddev() function initializes a seed, using the random(4) random number device which returns good random numbers, suitable for crypto-
     graphic use.

     The rand_r() function provides the same functionality as rand().  A pointer to the context value seed must be supplied by the caller.

SEE ALSO

     random(3), random(4)

STANDARDS

     The rand() and srand() functions conform to ISO/IEC 9899:1990 (``ISO C90'').

     The rand_r() function is as proposed in the POSIX.4a Draft #6 document.

BSD
								   May 25, 1999 							       BSD
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