Opened 2 years ago
Last modified 2 years ago
#28916 closed enhancement
MixedFormAlgebra  More Flexible Coercions — at Version 13
Reported by:  ghDeRhamSource  Owned by:  

Priority:  major  Milestone:  sage9.1 
Component:  geometry  Keywords:  manifolds, mixedforms 
Cc:  egourgoulhon, tscrim  Merged in:  
Authors:  Michael Jung  Reviewers:  
Report Upstream:  N/A  Work issues:  
Branch:  u/ghDeRhamSource/mixedformalgebra___more_flexible_coercions (Commits, GitHub, GitLab)  Commit:  ee4ad9352b5ac563b7ea1efde674d423ab8cc9b8 
Dependencies:  Stopgaps: 
Description (last modified by )
This makes the coercion model of mixed forms more robust against modifications regarding differential forms. For instance: As soon as all differential forms of another mixed form have a coerce map, the mixed form has one too. The same now holds for any algebraic element which is coercible into a single differential form.
At this stage, the method degree
is used and special cases are handled separately. But notice that not all coercible objects provide this method (symbolic ring). Or conversely, having this method doesn't mean being coercible into a differential form. Hence this invocation is now entirely avoided.
In particular we have:
sage: M = Manifold(2, 'M') sage: Omega = M.mixed_form_algebra() sage: Omega1 = M.diff_form_module(1) sage: T01 = M.tensor_field_module((0,1)) sage: Omega1.has_coerce_map_from(T01) True
But at this stage:
sage: Omega.has_coerce_map_from(T01) False
With this ticket:
sage: Omega.has_coerce_map_from(T01) True
Change History (13)
comment:1 Changed 2 years ago by
 Branch set to u/ghDeRhamSource/mixedformalgebra___more_flexible_coercions
comment:2 Changed 2 years ago by
 Cc egourgoulhon tscrim added
 Commit set to 4ba780eeb294c0390f3d83f1ffc355802590e018
 Component changed from PLEASE CHANGE to geometry
 Description modified (diff)
 Keywords manifolds mixedforms added
 Status changed from new to needs_review
 Type changed from PLEASE CHANGE to enhancement
comment:3 Changed 2 years ago by
 Commit changed from 4ba780eeb294c0390f3d83f1ffc355802590e018 to 3132acc35ea82346bafe2eecc81ca97f6adf5e2b
Branch pushed to git repo; I updated commit sha1. New commits:
3132acc  Trac 28916: Bugs fixed and code cleaned

comment:4 Changed 2 years ago by
I spared the try...except
block now completely. I think this is a negligible loss of computation time. Also this is more robust and works everytime.
comment:5 Changed 2 years ago by
 Commit changed from 3132acc35ea82346bafe2eecc81ca97f6adf5e2b to 6775b86a3a5c4dd10185bc1e7e2eb25136c31041
Branch pushed to git repo; I updated commit sha1. New commits:
6775b86  Trac 28916: try...except removed

comment:6 Changed 2 years ago by
comment:7 Changed 2 years ago by
Do you have some examples that demonstrates that this change now covers something that it didn't (correctly) do before? If so, please add them to the documentation, but if not, can you give a more detailed explanation as to why you think this is better?
comment:8 Changed 2 years ago by
Fair enough. I'm not sure this change covers even more at this stage.
The only improvement so far: There might be objects with a method degree
which are not coercible into differential forms. Or conversely there are coercible objects without having a degree method (like elements of the symbolic ring). So I avoid invoking degree
completely.
Assume in a future version there come more objects not having a degree
method but are coercible into differential forms (I admit, I have no idea what else it could be). Nevertheless, these cases have to be handled separately now. But with this changes, all potential coercions are covered.
Was that clearer? What do you think about it? And how could I improve my description?
By the way: Merry christmas retrospectively. :)
comment:9 Changed 2 years ago by
 Description modified (diff)
comment:10 Changed 2 years ago by
 Description modified (diff)
 Milestone changed from sage9.0 to sage9.1
comment:11 Changed 2 years ago by
 Commit changed from 6775b86a3a5c4dd10185bc1e7e2eb25136c31041 to ee4ad9352b5ac563b7ea1efde674d423ab8cc9b8
Branch pushed to git repo; I updated commit sha1. New commits:
ee4ad93  Merge branch 'develop' into t/28916/mixedformalgebra___more_flexible_coercions

comment:12 Changed 2 years ago by
Yes, that is more clear, thank you. So can you please add such an example that now coerces that previously did not?
This makes the coercion model of mixed forms more robust against modifications regarding differential forms. For instance: As soon as differential forms of every degree have coerce maps, the mixed form has one too.
New commits:
Trac 28916: Flexible coercion of mixed forms