Catch CDD errors during polyhedron construction

[vbraun]

As reported on ​https://groups.google.com/d/msg/sage-support/lsUODuV47kc/7O0CLf1_ywMJ, numerically unstable input is not treated correctly in CDD and it errors out instead. This patch detects the error and converts it into a ValueError

• Apply trac_14479_cdd_error.patch​
• Apply trac_14479_reviewer.patch​

[vbraun]

Initial patch

[dimpase]

Could you also add in the doctest

Polyhedron(point_list,base_ring=QQ)

and

Polyhedron(point_list,backend='ppl',base_ring=QQ)

to give people more hints how to avoid that error?

By the way, is there any reason for having cdd as the default backend? On this example it's more than 10 times slower than ppl.

[ncohen]

HMmmmmmmm... And isn't there something wrong with the "verbose" keywords you add to "init_from_Vrepresentation" and "init_from_Hrepresentation" ? You add them to the method, but you don't use them in the code that follows ! O_o

Nathann

[vbraun]

cdd is the only backend for floating-point numbers, and therefore the default. Does anybody know a better floating-point implementation?

The verbose keyword argument just wasn't patched through correctly.

[dimpase]

reviewer patch

[dimpase]

Replying to vbraun:

cdd is the only backend for floating-point numbers, and therefore the default. Does anybody know a better floating-point implementation?

The verbose keyword argument just wasn't patched through correctly.

do you mean to say that something needs to be fixed in your patch?

[vbraun]

No, I was just trying to explain why my patch adds the verbose keyword argument in some places.

Positive review to the reviewer patch.

[dimpase]

Replying to vbraun:

No, I was just trying to explain why my patch adds the verbose keyword argument in some places.

Positive review to the reviewer patch.

all looks good to me, positive review.

[ncohen]

What I don't get is why you would add a verbose arguments to methods that never use the verbose variable in their code O_o

Nathann

[vbraun]

Both Polyhedron_ppl and Polyhedron_cdd derive from Polyhedron_base. They both override _init_from_Vrepresentation. One of them doesn't (yet) do anything if you pass verbose=True`, but it should still accept the argument so that you can use the two derived classes interchangeably.