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ltl2tgba_fm: fix non-deterministic output

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The ltl_to_tgba_fm() translation function was using a hash_map of
maps (ugh!) to merge transitions on output.  However recent libstd++
changed the implementation of hash_map (a.k.a. unordered_map) causing
transitions to be output in a different order.  This
implementation-dependent order caused the ltl2ta.test to fail because
the BA->TA transformation can produce TA of different sizes if you
simply change the order of transitions in the input BA! This does not
sound like a nice property for the BA->TA transformation, but Ala Eddine
isn't sure how to fix it yet.  In the meantime, this patch makes sure
ltl_to_tgba_fm() will return the same output regardless of the
implementation of hash_map.

The ltl2ta.test failure has been observed with g++ 4.9.2 on Arch Linux,
and with gcc-snapshot (5.0.0 20141016) on Debian.

* src/tgbaalgos/ltl2tgba_fm.cc: Rewrite the transition merging
using a std::vector and std::sort instead of nested maps tables.
* src/tgbatest/ltl2ta.test: Adjust sizes to the new order.
* NEWS: Mention the fix.
This commit is contained in:
Alexandre Duret-Lutz 2014-11-13 18:03:15 +01:00
parent 63da386a66
commit 11aa708a81
3 changed files with 151 additions and 121 deletions
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@ -157,6 +157,10 @@ New in spot 1.2.5a (not yet released)
version 8.0 of Org-mode. (This was only a problem if you build
from the git repository, or if you want to edit the
documentation.)
- recent to changes to libstd++ (as shipped by g++ 4.9.2) have
demonstrated that the order of transitions output by the
LTL->TGBA translation used to be dependent on the implementation
of the STL. This is now fixed.
New in spot 1.2.5 (2014-08-21)