Re-add Epick_without_intervals

[lrineau]

Summary of Changes

New attempt for Epick_without_intervals. First attempt was #3939, reverted by commit bb640d2 in #4096.

This time, I made it with the right kernel base, I think.

Release Management

• Affected package(s): all

[mglisse]

Is the 'E' for "exact" true? It isn't clear where bignums appear in here.

[lrineau]

You are right. I messed up again.

[mglisse]

Mael had suggestions in #3939 (comment).

[MaelRL]

MaelRL@88ee987 is a proof of concept of what I meant. I only modified Orientation_3.

Running 'Kernel_23/test/Kernel_23/Cartesian' gives:

typeid k: N4CGAL5EpickE
static call in orientation_3
Calling base of static...
Calling a filtered predicate
Could not resolve with filtered predicate, calling base of filtered
typeid kiwi: N4CGAL23Epick_without_intervalsE
static call in orientation_3
Calling base of static...

[mglisse]

MaelRL@88ee987 is a proof of concept of what I meant.

Makes sense, but you will need a (trivial) functor for all remaining predicates to replace them with an exact version, not just a fallback for those that have a static filter. An alternative would be to decompose it into 2 wrappers: one that replaces all predicates with their exact counterpart, and one that interposes static filters on known predicates, but this split is probably not necessary.

[mglisse]

One simple way to get something like this is to modify Filtered_predicate and put everything but the last line of the body between #ifndef CGAL_NO_INTERVALS and #endif. Then you can just use Epick. (ok, probably this needs to be done in a few more places as well)

[MaelRL]

PR #4495 would also benefit from the same mechanism of Static_filters<CK> not automatically wrapping with Filtered_kernel_base. It uses a special type of filtering and cannot use CGAL::Filtered_predicate. For now, we have added (commit 46876c8) another class that omits this wrapping, but if changes from above were to be used it could be simply Static_filters<CK>.

@mglisse Since CGAL::Filtered_predicate is its own class, I don't know if we can handle everything with macros. Maybe just a template parameter to Filtered_kernel_base? But then wouldn't it look a bit weird with CGAL::Filtered_kernel_base<CK, DONT_FILTER>?

[mglisse]

@mglisse Since CGAL::Filtered_predicate is its own class, I don't know if we can handle everything with macros.

The idea of a macro was first as a quick proof of concept, and second that the only point of Epick_without_interval (for users) is as a replacement for Epick on platforms where we cannot use intervals (no rounded operations), so it might as well be called Epick, controlled by some macros.

Maybe just a template parameter to Filtered_kernel_base? But then wouldn't it look a bit weird with CGAL::Filtered_kernel_base<CK, DONT_FILTER>?

You can call it CGAL::Filtered_kernel_base<CK, NO_INTERVAL> if that looks less weird. In software pipelines, I have seen a few times functions that take an argument enable=true/false, so that the pipeline is structurally constant, but the behavior can be controlled. So I don't find it shocking anymore...

(I haven't looked at this since October, so I don't remember much, and I haven't looked at your other branch either, so don't take my comment as something insightful that needs to be analyzed)

[maxGimeno]

Is this PR ready for testing ?

[sloriot]

Travis fails

[MaelRL]

The implementation is wrong. If I have time, I will enhance internal::Static_filters like I said above (I did part of it in the Filtered rational kernel), and it can be finished that way.