On Thu, Nov 26, 2009 at 08:20:31PM +0100, Marie Rognes wrote:
Anders Logg wrote:
I made some fixes to UFL and FFC to allow auto-detection of degree and
shape for all types of elements.
I also changed in expression.py in DOLFIN to use Lagrange by default
instead of Quadrature. The Poisson demo now works with the new simple
Expression interface:
f = Expression("10*exp(-(pow(x[0] - 0.5, 2) + pow(x[1] - 0.5, 2)) / 0.02)")
g = Expression("sin(5*x[0])")
Nice :)
No need for V=V anymore.
Can one still use V=V if one wants to prescribe a function space?
Yes, one can do things like
f = Expression(("sin(5*x[0])"), ("cos(x[1])"), element=FiniteElement("BDM", triangle, 10))
or just
f = Expression(("sin(5*x[0])"), ("cos(x[1])"), degree=5)
I think it would be ok to use Lagrange by default.
Lagrange yes, but maybe higher order? (Using the same (or lower)
order for input
data as the discretization tends to be slightly dangerous.)
Any input on how it should be chosen is appreciated!
All the logic is in the function _adjust_elements in compiler.py in FFC:
def _adjust_elements(form_data):
"Adjust cell and degree for elements when unspecified"
# Extract common cell
common_cell = form_data.cell
if common_cell.domain() is None:
error("Missing cell definition in form.")
# Extract common degree
degrees = [metadata["quadrature_order"] for metadata in form_data.metadata.itervalues()]
degrees = [q for q in degrees if not q is None]
if degrees:
common_degree = max(degrees)
else:
common_degree = default_quadrature_degree
# Set cell and degree if missing
for element in form_data.elements:
# Check if cell and degree need to be adjusted
cell = element.cell()
degree = element.degree()
if degree is None:
info("Adjusting element degree from %s to %d" % (istr(degree), common_degree))
element.set_degree(common_degree)
if cell.domain() is None:
info("Adjusting element cell from %s to %s." % (istr(cell), str(common_cell)))
element.set_cell(common_cell)
Please help out to get this right.
