On 8 June 2011 14:29, Martin Sandve Alnæs <[email protected]> wrote: > On 8 June 2011 14:18, Kristian Ølgaard <[email protected]> wrote: >> On 8 June 2011 14:08, Martin Sandve Alnæs <[email protected]> wrote: >>> On 8 June 2011 13:55, Martin Sandve Alnæs <[email protected]> wrote: >>>> On 8 June 2011 13:46, Kristian Ølgaard <[email protected]> wrote: >>>>> On 8 June 2011 13:31, Martin Sandve Alnæs <[email protected]> wrote: >>>>>> On 8 June 2011 13:11, Kristian Ølgaard <[email protected]> wrote: >>>>>>> On 8 June 2011 12:11, Martin Sandve Alnæs <[email protected]> wrote: >>>>>>>> Done and checked in. If someone updates FFC to support this, we can >>>>>>>> hopefully close this bug. >>>>>>> >>>>>>> I'm not sure this is enough to handle the bug. If you look at the >>>>>>> output of printing M in the example code I posted you'll see that the >>>>>>> list tensor contains component '7'. This is what you'll get from >>>>>>> calling self.component(), but the >>>>>>> TT.symmetry() only contains: >>>>>>> {(2,): (1,), (6,): (5,)} >>>>>>> >>>>>>> Is there some function we need to call first to map the component '7' >>>>>>> --> '6', before looking at symmetries to map '6' --> '5'? >>>>>>> Doing so will get us into trouble with mapping '3' --> '2' since >>>>>>> symmetry will map that to '1'. >>>>>>> The TT element has 2 x 3 sub elements due to symmetry. >>>>>> >>>>>> The 7 is an index into the value index space of the coefficient and is >>>>>> correct. It has nothing (directly) to do with subelement indexing. I >>>>>> think you're assuming a closer relation between them than there is? >>>>>> Let me try to clear it up... >>>>>> >>>>>> The value index space is contiguous from the point of view of UFL >>>>>> expressions, but has holes when symmetries are considered. The >>>>>> noncontiguous value index space will then need to be mapped to a >>>>>> contiguous subelement space by associating each value index that is >>>>>> not in the symmetry mapping with a subelement index. >>>>>> >>>>>> 1) We have a component/value index >>>>>> 2) We map that value index to another value index using a symmetry >>>>>> mapping (e.g. 6->5 and 7->7 in your example) >>>>>> 3) We map from the noncontiguous value index space to the contiguous >>>>>> subelement index space >>>>>> >>>>>> Clear as mud? :) >>>>> >>>>> Yes, but since we only deal with the (sub)elements that are actually >>>>> present in FFC, it's really inconvenient that we can't get a mapping >>>>> from the component to the subelement. >>>>> I somehow suspected the FiniteElement.extract_component() to do this, >>>>> but it turns out not to be the case. >>>>> >>>>>> UFL handles (2) for you only when you apply expand_indices. >>>>>> >>>>>> FFC will have to handle (3) when generating code, it doesn't touch >>>>>> anything UFL needs to know about. I'll see if I can whip up a quick >>>>>> utility function for it though. >>>>> >>>>> That would really be nice. >>>> >>>> Done :) The latest patch contains code and test showing usage. >>>> >>>> But maybe it should be integrated into extract_component, I'll take a >>>> look at that now that I'm into this. >>> >>> I applied the symmetry mapping inside extract_component for tensor elements, >>> that way you shouldn't have to do the symmetry mapping in addition to >>> calling extract_component. The numbering utility I checked in could still >>> come in handy though, so I'll let it stay. >> >> OK, will you add the numbering utility function in extract_component such >> that >> calling this function will return the contiguous component and element? > > Hm... I'd rather keep extract_component as it is, returning > the value component tuple and not the element numbering. > > Just do > v, s = build_component_numbering(e.value_shape(), e.symmetry()) > sc, sube = e.extract_component(c) > sub_element_index = v[sc]
OK, I'll see if I can figure out where to add this. Kristian > Martin > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
