What does "nan" mean?

[skyglin]

My program has a matrix of floating point values, after I performed calculations to each element in the matrix, when I print out using printf() some of the elements turned out to have the value "nan", what does nan mean?

My code is as follows:

float local_force[M][N];
        /* compute the forces on each of the N particles on each processor */
        for (i = 0; i < M; i++) {
                for (j = 0; j < N; j++) {
                        if ( recv_xPos[i] == xPos[j] &&  recv_yPos[i] == yPos[j])
                                local_force[i][j] = 0;             /* 0 represent infinite force in newton */
                        else
                        {
                                float xDis = absolute(recv_xPos[i] - xPos[j]);
                                float yDis = absolute(recv_yPos[i] - yPos[j]);
                                radius_square = pow(xDis, 2) + pow(yDis, 2);
                                local_force[i][j] = (recv_charge[i] * charge[j]) / radius_square;
                        }
                }
        }

Please use [code][/code]Tags

[skyglin]

Thanks, this is what I needed. yeah!!