Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

State Space Compression in History 269
intrinsic final markings. Therefore in a compressed schedule they can be
merged in a single transition corresponding to the final result of firing L1 or
L2. Note, that such merging is not possible by any known reduction technique
based on structural information solely. It is a combination of structural and
behavioural information that significantly expands the capabilities of reduction.
Let us formally check whether they can be fired from the initial marking
shown in Figure 20-3.
The marking sequence of a path L1 e.g. is
From this
sequence one computes the consumption indexes:
while for the rest of the places the consumption indexes
are 0. Then, following Property 2 it is easy to conclude that transitions from
the path L1 are fireable under the initial marking of Figure 20-3.
Trace-based and path-based compressions are appealing techniques to
reduce the complexity of scheduling procedures. An orthogonal approach for
simplification of schedules is presented in next section.
5. AVOIDING REPETITION OF SCHEDULE STATES
In the conventional procedure from [2] during generation of a schedule its
states are pruned looking at their prehistory only. Due to choices in a specification,
the states with the same markings could be generated in alternative
branches of computation. Because of this some compression possibilities might
be overlooked. This section suggests an improvement over the conventional
algorithm by removing repeated markings from alternative branches as well.
Due to the special constraints that our synthesis application presents, the
approach we have finally implemented to reduce the exploration space is based
on hash tables. Hash tables are a much less complex method to store old