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to_parity: only call reduce_parity() when prefix_parity is enabled

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Calling reduce_parity() in to_parity() is confusing, because then
running to_parity() on one SCC does not necessarily produce the same
output as running to_parity() on the entire automaton.  However it is
necessary for the implementation of parity_prefix.  As a compromise,
disable reduce_parity() when parity_prefix is disabled, this way we
can use that to demonstrate how the algorithm works.

* spot/twaalgos/toparity.hh, spot/twaalgos/toparity.cc: Do not
call reduce_parity() when parity_prefix is disabled.
* tests/python/toparity.py: Adjust.
This commit is contained in:
Alexandre Duret-Lutz 2020-04-17 15:20:53 +02:00
parent 102ef04364
commit fd0d752bc3
3 changed files with 46 additions and 20 deletions
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36
spot/twaalgos/toparity.hh
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@ -31,16 +31,16 @@ namespace spot
/// several elements in a record, it tries to find an order such
/// that the new permutation already exists.
bool search_ex = true;
/// If \a use_last is true and \a search_ex are true, we use the
/// If \c use_last is true and \a search_ex are true, we use the
/// most recent state when we find multiple existing state
/// compatible with the current move.
bool use_last = true;
/// If \a force_order is true, we force to use an order when CAR or IAR is
bool use_last = true;
/// If \c force_order is true, we force to use an order when CAR or IAR is
/// applied. Given a state s and a set E ({0}, {0 1}, {2} for example) we
/// construct an order on colors. With the given example, we ask to have
/// a permutation that start with [0 …], [0 1 …] or [2 …] in
/// that order of preference.
bool force_order = true;
bool force_order = true;
/// If \c partial_degen is true, apply a partial
/// degeneralization to remove occurrences of acceptance
/// subformulas such as `Fin(x) | Fin(y)` or `Inf(x) & Inf(y)`.
@ -51,15 +51,25 @@ namespace spot
/// If \c scc_acc_clean is true, to_parity() will ignore colors
/// no occoring in an SCC while processing this SCC.
bool acc_clean = true;
/// If \a parity_equiv is true, to_parity() will check if there
/// If \c parity_equiv is true, to_parity() will check if there
/// exists a permutations of colors such that the acceptance
/// condition is a parity condition.
bool parity_equiv = true;
/// If \a parity_prefix is true, to_parity() will remove the prefix of
/// the acceptance condition that correspond to parity, works on the
// remaining and adds marks to process the prefix.
bool parity_prefix = true;
/// If \a rabin_to_buchi is true, to_parity() tries to convert a Rabin or
bool parity_equiv = true;
/// If \c parity_prefix is true, to_parity() will use a special
/// handling for acceptance conditions of the form `Inf(m0) |
/// (Fin(m1) & (Inf(m2) | (… β)))` that start as a parity
/// condition (modulo a renumbering of `m0`, `m1`, `m2`, ...) but where
/// `β` can be an arbitrary formula. In this case, the paritization
/// algorithm is really applied only to `β`, and the marks of the
/// prefix are appended after a suitable renumbering.
///
/// For technical reasons, activating this option (and this is the
/// default) causes reduce_parity() to be called at the end to
/// minimize the number of colors used. It is therefore
/// recommended to disable this option when one wants to follow
/// the output CAR/IAR constructions.
bool parity_prefix = true;
/// If \c rabin_to_buchi is true, to_parity() tries to convert a Rabin or
/// Streett condition to Büchi or co-Büchi with
/// rabin_to_buchi_if_realizable().
bool rabin_to_buchi = true;
@ -69,8 +79,8 @@ namespace spot
/// Use propagate_marks_here to increase the number of marks on transition
/// in order to move more colors (and increase the number of
/// compatible states) when we apply LAR.
bool propagate_col = true;
/// If \a pretty_print is true, states of the output automaton are
bool propagate_col = true;
/// If \c pretty_print is true, states of the output automaton are
/// named to help debugging.
bool pretty_print = false;
};