[7314] in Athena Bugs
vax 7.2R: gcc
daemon@ATHENA.MIT.EDU (daemon@ATHENA.MIT.EDU)
Thu Mar 14 22:40:56 1991
From: jldelcal@ATHENA.MIT.EDU
To: bugs@ATHENA.MIT.EDU
Date: Thu, 14 Mar 91 22:40:37 EST
System name: test-2000
Type and version: VAXSTAR 7.2R
Display type: SM
What were you trying to do?
run one of my programs compiled using gcc. here is a sample:
#include<stdio.h>
#include<math.h>
#define MASS 4e3
#define BIGK 4e6
#define PI 3.1415927
void create_k_inverse_x1_and_m(double *K, double *M, double x1[], int n);
void sqr_mat_vec_mult(double *A, double b[], double c[], int n);
double find_max_in_vec(double x[], int n);
void scale_vec(double x[], double scale, int n);
double do_iterations(double tolerance, int n);
double do_one_iteration(double *K, double *M, double x1[], int n);
main()
{
int height;
double tolerance, fn;
printf("enter desired tolerance: ");
scanf("%lf", &tolerance);
printf("\nenter number of storeys of building: ");
scanf("%i", &height); /*an error occurs just after this */
/*before do_iterations is called */
/*it signals floating exception */
/*without any operation on a float*/
fn = do_iterations(tolerance, height);
printf("\nfn = %lf\n", fn);
}
double do_iterations(double tolerance, int n)
{
double K[n][n], M[n][n], x1[n];
int i;
double omega, omegaprev, t1, fn;
printf("chkpt");
omegaprev = do_one_iteration(&K[0][0], &M[0][0], x1, n);
omega = do_one_iteration(&K[0][0], &M[0][0], x1, n);
t1 = fabs(omega - omegaprev);
create_k_inverse_x1_and_m(&K[0][0], &M[0][0], x1, n);
while (t1 > tolerance){
printf("%8.4lf\n", t1);
omegaprev = omega;
omega = do_one_iteration(&K[0][0], &M[0][0], x1, n);
t1 = fabs(omega - omegaprev);
}
fn = sqrt(omega)/(2*PI);
return(fn);
}
double do_one_iteration(double *K, double *M, double x1[], int n)
{
double q[n], phi[n];
double omega;
printf("hurro");
sqr_mat_vec_mult(M, x1, q, n);
sqr_mat_vec_mult(K, q, phi, n);
omega = find_max_in_vec(x1, n) / find_max_in_vec(phi, n);
return(omega);
}
void scale_vec(double x[], double scale, int n)
{
int i;
for(i=0; i<n; i++)
x[i] = x[i] * scale;
}
void create_k_inverse_x1_and_m(double *K, double *M, double x1[], int n)
{
int i, j;
double invk = 1 / BIGK;
for(i=0; i<n; i++){
for(j=i; j<n; j++){
*(M+i*n+j) = 0;
*(K+i*n+j) = (i + 1) * invk;
}
for(j=i+1; j<n; j++){
*(M+j*n+i) = 0;
*(K+j*n+i) = (i + 1) * invk;
}
*(M+i*n+i) = MASS;
x1[i] = 1;
}
}
void sqr_mat_vec_mult(double *A, double b[], double c[], int n)
{
double sum;
int i,j;
for(i=0; i<n; i++){
sum = 0.0;
for(j=0; j<n; j++)
sum = sum + *(A+i*n+j)*b[j];
c[i] = sum;
}
}
double find_max_in_vec(double x[], int n)
{
double max;
int i;
max = x[0];
for(i=1; i<n; i++)
if (x[i] > max)
max = x[i];
return(max);
}
What's wrong:
it signalled floating exception where commented. i put checkpoints to find out
where it happened. this is where the error occured.
What should have happened:
any error message, if any, should not have been signalled from the area pointed
out by the comment.
Please describe any relevant documentation references:
the program is above.
