int main ( int argc, char *argv[] )
/******************************************************************************/
/*
Purpose:
MAIN is the main program for CLENSHAW_CURTIS_RULE.
Discussion:
This program computes a standard Clenshaw Curtis quadrature rule
and writes it to a file.
The user specifies:
* the ORDER (number of points) in the rule;
* A, the left endpoint;
* B, the right endpoint;
* FILENAME, which defines the output filenames.
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
01 October 2012
Author:
John Burkardt
*/
{
double a;
double b;
char filename[255];
int order;
double *r;
double *w;
double *x;
timestamp ( );
printf ( "\n" );
printf ( "CLENSHAW_CURTIS_RULE\n" );
printf ( " C version\n" );
printf ( "\n" );
printf ( " Compute a Clenshaw Curtis rule for approximating\n" );
printf ( " Integral ( -1 <= x <= +1 ) f(x) dx\n" );
printf ( " of order ORDER.\n" );
printf ( "\n" );
printf ( " The user specifies ORDER, A, B and FILENAME.\n" );
printf ( "\n" );
printf ( " ORDER is the number of points.\n" );
printf ( " A is the left endpoint.\n" );
printf ( " B is the right endpoint.\n" );
printf ( " FILENAME is used to generate 3 files:\n" );
printf ( " filename_w.txt - the weight file\n" );
printf ( " filename_x.txt - the abscissa file.\n" );
printf ( " filename_r.txt - the region file.\n" );
/*
Get ORDER.
*/
if ( 1 < argc )
{
order = atoi ( argv[1] );
}
else
{
printf ( "\n" );
printf ( " Enter the value of ORDER (1 or greater)\n" );
scanf ( "%d", &order );
}
/*
Get A.
*/
if ( 2 < argc )
{
a = atof ( argv[2] );
}
else
{
printf ( "\n" );
printf ( " Enter the left endpoint A:\n" );
scanf ( "%lf", &a );
}
/*
Get B.
*/
if ( 3 < argc )
{
b = atof ( argv[3] );
}
else
{
printf ( "\n" );
printf ( " Enter the right endpoint B:\n" );
scanf ( "%lf", &b );
}
/*
Get FILENAME:
*/
if ( 4 < argc )
{
strcpy ( filename, argv[4] );
}
else
{
printf ( "\n" );
printf ( " Enter FILENAME, the \"root name\" of the quadrature files).\n" );
scanf ( "%s", filename );
}
/*
Input summary.
*/
printf ( "\n" );
printf ( " ORDER = %d\n", order );
printf ( " A = %g\n", a );
printf ( " B = %g\n", b );
printf ( " FILENAME = \"%s\".\n", filename );
/*
Construct the rule.
*/
r = ( double * ) malloc ( 2 * sizeof ( double ) );
w = ( double * ) malloc ( order * sizeof ( double ) );
x = ( double * ) malloc ( order * sizeof ( double ) );
r[0] = a;
r[1] = b;
clenshaw_curtis_compute ( order, x, w );
/*
Rescale the rule.
*/
rescale ( a, b, order, x, w );
/*
Output the rule.
*/
rule_write ( order, filename, x, w, r );
/*
Free memory.
*/
free ( r );
free ( w );
free ( x );
/*
Terminate.
*/
printf ( "\n" );
printf ( "CLENSHAW_CURTIS_RULE:\n" );
printf ( " Normal end of execution.\n" );
printf ( "\n" );
timestamp ( );
return 0;
}
int main_old ( int argc, char *argv[] )
{
double a;
double alpha;
double b;
double beta;
char filename[255];
int kind;
int order;
double *r;
double *w;
double *x;
printf ( "\n" );
printf ( "legendre_rule\n" );
printf ( " c version\n" );
printf ( "\n" );
/*printf ( " compiled on %s at %s.\n", __date__, __time__ );*/
printf ( "\n" );
printf ( " compute a gauss-legendre rule for approximating\n" );
printf ( "\n" );
printf ( " integral ( a <= x <= b ) f(x) dx\n" );
printf ( "\n" );
printf ( " of order order.\n" );
printf ( "\n" );
printf ( " the user specifies order, a, b and filename.\n" );
printf ( "\n" );
printf ( " order is the number of points.\n" );
printf ( "\n" );
printf ( " a is the left endpoint.\n" );
printf ( "\n" );
printf ( " b is the right endpoint.\n" );
printf ( "\n" );
printf ( " filename is used to generate 3 files:\n" );
printf ( "\n" );
printf ( " filename_w.txt - the weight file\n" );
printf ( " filename_x.txt - the abscissa file.\n" );
printf ( " filename_r.txt - the region file.\n" );
/*
initialize parameters;
*/
alpha = 0.0;
beta = 0.0;
/*
get order.
*/
if ( 1 < argc )
{
order = atoi ( argv[1] );
}
else
{
printf ( "\n" );
printf ( " enter the value of order (1 or greater)\n" );
scanf ( "%d", &order );
}
/*
get a.
*/
if ( 2 < argc )
{
a = atof ( argv[2] );
}
else
{
printf ( "\n" );
printf ( " enter the value of a:\n" );
scanf ( "%lf", &a );
}
/*
get b.
*/
if ( 3 < argc )
{
b = atof ( argv[3] );
}
else
{
printf ( "\n" );
printf ( " enter the value of b:\n" );
scanf ( "%lf", &b );
}
/*
get filename:
*/
if ( 4 < argc )
{
strcpy ( filename, argv[4] );
}
else
{
printf ( "\n" );
printf ( " enter filename, the \"root name\" of the quadrature files).\n" );
scanf ( "%s", filename );
}
/*
input summary.
*/
printf ( "\n" );
printf ( " order = %d\n", order );
printf ( " a = %g\n", a );
printf ( " b = %g\n", b );
printf ( " filename = \"%s\".\n", filename );
/*
construct the rule.
*/
w = ( double * ) malloc ( order * sizeof ( double ) );
x = ( double * ) malloc ( order * sizeof ( double ) );
kind = 1;
cgqf ( order, kind, alpha, beta, a, b, x, w );
/*
write the rule.
*/
r = ( double * ) malloc ( 2 * sizeof ( double ) );
r[0] = a;
r[1] = b;
rule_write ( order, filename, x, w, r );
/*
free memory.
*/
free ( r );
free ( w );
free ( x );
/*
terminate.
*/
printf ( "\n" );
printf ( "legendre_rule:\n" );
printf ( " normal end of execution.\n" );
printf ( "\n" );
return 0;
}
