CostModel lookup failed

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Isaac DeFrain

Feb 11, 2021, 5:10:10 PMFeb 11
Hello TLA+ community,

I've been encountering this message while checking models with temporal properties using the command-line version of TLC:

CostModel lookup failed for expression <line #, col # to line #, col # of module B>. Reporting costs into <line #, col # to line #, col # of module A> instead (Safety and Liveness checking is unaffected. Please report a bug.)

Note: I've substituted #'s for the reported line and col numbers.

Since I'm not sure what is meant by "CostModel lookup", I'm not sure what details are essential to report here. If it makes any difference, module A EXTENDS module B.

My questions:
  1. What is this CostModel lookup?
  2. Is this really a bug that I should report?
  3. Has anyone else encountered this message?

Thanks in advance!


Isaac DeFrain

Markus Kuppe

Feb 11, 2021, 7:01:28 PMFeb 11
Hi Isaac,

please consider adding your spec and model to the relevant Github issue
[1]. The warning is "mostly harmless", saying that coverage/profiling
information will be off for the locations mentioned in the warning.

If you don't care about coverage/profiling [2], run TLC without the
"-coverage" parameter.



Leslie Lamport

Feb 11, 2021, 7:06:10 PMFeb 11
Hi Markus,

Since it appears that a significant number of people run TLC from the command line, it seems like a bad idea to make the -coverage option produce the reams of output needed for profiling. In fact, why should that output be produced if TLC isn't being called in -tool mode?


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