def compute_cat( self, ret_iw_dir=False ):
"""Compute the Christoffel acoustic tensor, given the incident wave
direction."""
opts = self.app_options
iw_dir = nm.array( opts.incident_wave_dir, dtype = nm.float64 )
dim = self.problem.get_dim()
assert_( dim == iw_dir.shape[0] )
iw_dir = iw_dir / nla.norm( iw_dir )
if self.cached_christoffel is not None:
christoffel = self.cached_christoffel
else:
coefs = self.eval_homogenized_coefs()
christoffel = compute_cat( coefs, iw_dir,
self.app_options.dispersion )
report_iw_cat( iw_dir, christoffel )
self.cached_christoffel = christoffel
if ret_iw_dir:
return christoffel, iw_dir
else:
return christoffel
