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Bug 468

Summary:	Wrong transition selection in systems with process priorities
Product:	UPPAAL	Reporter:	Yasufumi Suzuki <yasufumi.suzuki.bq>
Component:	Engine	Assignee:	Alexandre David <adavid>
Status:	RESOLVED FIXED
Severity:	major
Priority:	P2
Version:	4.0.7
Hardware:	PC
OS:	Windows XP
Architecture:
Attachments:	Example model Example trace

Description Yasufumi Suzuki 2009-04-03 08:40:46 CEST

A binary synchronization transition of a low priority process  is 
enabled even if a binary synchronization transition of a higher priority 
process using the same channel is possible.

Problem description:
This problem occurs only when also a delaying transition in a third 
process is enabled.
It is visible in the last transition in the attached  example trace.

Example model: see attachment 1 [details]
Example trace: see attachment 2 [details]

Comment 1 Yasufumi Suzuki 2009-04-03 08:42:04 CEST

Created attachment 214 [details]
Example model

Comment 2 Yasufumi Suzuki 2009-04-03 08:42:45 CEST

Created attachment 215 [details]
Example trace

Comment 3 Alexandre David 2009-08-12 19:05:53 CEST

Fixed in rev. 4378 (4.0.9) and 4379 (trunk).
We have changed the semantics because it was inconsistent.
Before, priority was resolved by comparing the priorities of
the processes involved in two transitions by descending order.
Now, it is resolved by considering the highest priority process,
which is in line with priority ceiling protocols.

In this example, it is normal to have the synchronization with
the new semantics (though not normal with the old one).