void
Curve::getstepsize( void )
{
minstepsize= 0;
if( mapdesc->isConstantSampling() ) {
// fixed number of samples per patch in each direction
// maxrate is number of s samples per patch
setstepsize( mapdesc->maxrate );
} else if( mapdesc->isDomainSampling() ) {
// maxrate is number of s samples per unit s length of domain
setstepsize( mapdesc->maxrate * range[2] );
} else {
// upper bound on path length between sample points
assert( order <= MAXORDER );
/* points have been transformed, therefore they are homogeneous */
REAL tmp[MAXORDER][MAXCOORDS];
const int tstride = sizeof(tmp[0]) / sizeof(REAL);
int val = mapdesc->project( spts, stride, &tmp[0][0], tstride, order );
if( val == 0 ) {
// control points cross infinity, therefore derivatives are undefined
setstepsize( mapdesc->maxrate );
} else {
REAL t = mapdesc->getProperty( N_PIXEL_TOLERANCE );
if( mapdesc->isParametricDistanceSampling() ) {
REAL d = mapdesc->calcPartialVelocity( &tmp[0][0], tstride, order, 2, range[2] );
stepsize = (d > 0.0) ? ::sqrtf( 8.0 * t / d ) : range[2];
minstepsize = ( mapdesc->maxrate > 0.0 ) ? (range[2] / mapdesc->maxrate) : 0.0;
} else if( mapdesc->isPathLengthSampling() ) {
// t is upper bound on path (arc) length
REAL d = mapdesc->calcPartialVelocity( &tmp[0][0], tstride, order, 1, range[2] );
stepsize = ( d > 0.0 ) ? (t / d) : range[2];
minstepsize = ( mapdesc->maxrate > 0.0 ) ? (range[2] / mapdesc->maxrate) : 0.0;
} else {
// control points cross infinity, therefore partials are undefined
setstepsize( mapdesc->maxrate );
}
}
}
}
int Integrator::dointstep(int (*func)(double, const double*, double*, void*), IntParams ¶ms, double data[], double &time, const double endtime) {
// Integrates a single step
// Sets up the system to integrate, including the function that specifies the derivatives, NULL for the Jacobian, the number of elements
// being integrated, and the parameters to pass through to the function
gsl_odeiv2_system sys = { func, NULL, numelements, ¶ms };
// Make a copy of the stepsize - the evolution function wants to update this quantity, but a reference to the class' private information
// makes things unhappy
double stepsizecopy = stepsize;
// Actually take the integration step
int status = gsl_odeiv2_evolve_apply(evolve, control, step, &sys, &time, endtime, &stepsizecopy, data);
// Update the stepsize according to what GSL thinks will work well, but make sure it doesn't get too big. We want some resolution on our functions!
setstepsize(stepsizecopy);
// Return the status: should be GSL_SUCCESS if everything worked
return status;
}
