void r8_test ( int logn_max )
/******************************************************************************/
/*
Purpose:
R8_TEST estimates the value of PI using double.
Discussion:
PI is estimated using N terms. N is increased from 10^2 to 10^LOGN_MAX.
The calculation is repeated using both sequential and Open MP enabled code.
Wall clock time is measured by calling SYSTEM_CLOCK.
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
13 November 2007
Author:
John Burkardt
*/
{
double error;
double estimate;
int logn;
char mode[4];
int n;
double r8_pi = 3.141592653589793;
double wtime;
printf ( "\n" );
printf ( "R8_TEST:\n" );
printf ( " Estimate the value of PI,\n" );
printf ( " using double arithmetic.\n" );
printf ( "\n" );
printf ( " N = number of terms computed and added;\n" );
printf ( "\n" );
printf ( " MODE = SEQ for sequential code;\n" );
printf ( " MODE = OMP for Open MP enabled code;\n" );
printf ( " (performance depends on whether Open MP is used,\n" );
printf ( " and how many processes are available)\n" );
printf ( "\n" );
printf ( " ESTIMATE = the computed estimate of PI;\n" );
printf ( "\n" );
printf ( " ERROR = ( the computed estimate - PI );\n" );
printf ( "\n" );
printf ( " TIME = elapsed wall clock time;\n" );
printf ( "\n" );
printf ( " Note that you can''t increase N forever, because:\n" );
printf ( " A) ROUNDOFF starts to be a problem, and\n" );
printf ( " B) maximum integer size is a problem.\n" );
printf ( "\n" );
printf ( " N Mode Estimate Error Time\n" );
printf ( "\n" );
n = 1;
for ( logn = 1; logn <= logn_max; logn++ )
{
/*
Note that when I set N = 10**LOGN directly, rather than using
recursion, I got inaccurate values of N when LOGN was "large",
that is, for LOGN = 10, despite the fact that N itself was
a KIND = 8 integer!
Sequential calculation.
*/
strcpy ( mode, "SEQ" );
wtime = omp_get_wtime ( );
estimate = r8_pi_est_seq ( n );
wtime = omp_get_wtime ( ) - wtime;
error = r8_abs ( estimate - r8_pi );
printf ( "%14d %s %14f %14g %14f\n", n, mode, estimate, error, wtime );
/*
Open MP enabled calculation.
*/
strcpy ( mode, "OMP" );
wtime = omp_get_wtime ( );
estimate = r8_pi_est_omp ( n );
wtime = omp_get_wtime ( ) - wtime;
error = r8_abs ( estimate - r8_pi );
printf ( "%14d %s %14f %14g %14f\n", n, mode, estimate, error, wtime );
n = n * 10;
}
return;
}
void r8_test ( int logn_max )
{
double error;
double estimate;
int logn;
char mode[4];
int n;
double r8_pi = 3.141592653589793;
double wtime;
printf ( "\n" );
printf ( "R8_TEST:\n" );
printf ( " Estimate the value of PI,\n" );
printf ( " using double arithmetic.\n" );
printf ( "\n" );
printf ( " N = number of terms computed and added;\n" );
printf ( "\n" );
printf ( " MODE = SEQ for sequential code;\n" );
printf ( " MODE = OMP for Open MP enabled code;\n" );
printf ( " (performance depends on whether Open MP is used,\n" );
printf ( " and how many processes are available)\n" );
printf ( "\n" );
printf ( " ESTIMATE = the computed estimate of PI;\n" );
printf ( "\n" );
printf ( " ERROR = ( the computed estimate - PI );\n" );
printf ( "\n" );
printf ( " TIME = elapsed wall clock time;\n" );
printf ( "\n" );
printf ( " Note that you can''t increase N forever, because:\n" );
printf ( " A) ROUNDOFF starts to be a problem, and\n" );
printf ( " B) maximum integer size is a problem.\n" );
printf ( "\n" );
printf ( " N Mode Estimate Error Time\n" );
printf ( "\n" );
n = 1;
for ( logn = 1; logn <= logn_max; logn++ )
{
strcpy ( mode, "SEQ" );
wtime = omp_get_wtime ( );
estimate = r8_pi_est_seq ( n );
wtime = omp_get_wtime ( ) - wtime;
error = r8_abs ( estimate - r8_pi );
printf ( "%14d %s %14f %14g %14f\n", n, mode, estimate, error, wtime );
/*
Open MP enabled calculation.
*/
strcpy ( mode, "OMP" );
wtime = omp_get_wtime ( );
estimate = r8_pi_est_omp ( n );
wtime = omp_get_wtime ( ) - wtime;
error = r8_abs ( estimate - r8_pi );
printf ( "%14d %s %14f %14g %14f\n", n, mode, estimate, error, wtime );
n = n * 10;
}
return;
}
