Timeout due to excessive shrinking in Lin Bytes test with Domain on Cygwin

[jmid]

On the merge to main of #517 we saw a timeout on Cygwin trunk due to excessive shrinking in the Lin Bytes test with Domain test:
https://github.com/ocaml-multicore/multicoretests/actions/runs/12796162913/job/35675203217

random seed: 306961601
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 1000     0.0s Lin Bytes test with Domain
[ ]    0    0    0    0 / 1000     0.0s Lin Bytes test with Domain (generating)
[ ]   85    0    0   85 / 1000    62.4s Lin Bytes test with Domain (shrinking:    3.0014)
[ ]   85    0    0   85 / 1000   125.7s Lin Bytes test with Domain (shrinking:    5.0022)
[ ]   85    0    0   85 / 1000   186.3s Lin Bytes test with Domain (shrinking:    6.0025)
[ ]   85    0    0   85 / 1000   250.2s Lin Bytes test with Domain (shrinking:    7.0002)
[ ]   85    0    0   85 / 1000   312.7s Lin Bytes test with Domain (shrinking:    9.0003)
[ ]   85    0    0   85 / 1000   374.2s Lin Bytes test with Domain (shrinking:    9.0030)
[ ]   85    0    0   85 / 1000   434.2s Lin Bytes test with Domain (shrinking:   12.0004)
[ ]   85    0    0   85 / 1000   494.3s Lin Bytes test with Domain (shrinking:   19.0051)
[ ]   85    0    0   85 / 1000   554.5s Lin Bytes test with Domain (shrinking:   31.0010)
[ ]   85    0    0   85 / 1000   614.6s Lin Bytes test with Domain (shrinking:   41.0003)
[ ]   85    0    0   85 / 1000   678.1s Lin Bytes test with Domain (shrinking:   44)
[ ]   85    0    0   85 / 1000   780.8s Lin Bytes test with Domain (shrinking:   46)
[ ]   85    0    0   85 / 1000   881.0s Lin Bytes test with Domain (shrinking:   47)
[ ]   85    0    0   85 / 1000   969.1s Lin Bytes test with Domain (shrinking:   48)
[ ]   85    0    0   85 / 1000  1045.8s Lin Bytes test with Domain (shrinking:   49)
[ ]   85    0    0   85 / 1000  1114.6s Lin Bytes test with Domain (shrinking:   53)
[ ]   85    0    0   85 / 1000  1174.7s Lin Bytes test with Domain (shrinking:   56.0014)
[ ]   85    0    0   85 / 1000  1244.6s Lin Bytes test with Domain (shrinking:   60)
[ ]   85    0    0   85 / 1000  1320.1s Lin Bytes test with Domain (shrinking:   64)
[ ]   85    0    0   85 / 1000  1380.2s Lin Bytes test with Domain (shrinking:   69.0004)
[ ]   85    0    0   85 / 1000  1440.2s Lin Bytes test with Domain (shrinking:   73.0066)
[ ]   85    0    0   85 / 1000  1500.3s Lin Bytes test with Domain (shrinking:   84.0007)
[ ]   85    0    0   85 / 1000  1560.4s Lin Bytes test with Domain (shrinking:  112.0005)
[ ]   85    0    0   85 / 1000  1620.6s Lin Bytes test with Domain (shrinking:  134.0023)
[ ]   85    0    0   85 / 1000  1680.6s Lin Bytes test with Domain (shrinking:  151.0016)
[ ]   85    0    0   85 / 1000  4331.4s Lin Bytes test with Domain (shrinking:  165.0010)
[ ]   85    0    0   85 / 1000  4396.8s Lin Bytes test with Domain (shrinking:  165.0012)
[ ]   85    0    0   85 / 1000  4456.9s Lin Bytes test with Domain (shrinking:  177.0024)
[ ]   85    0    0   85 / 1000  4517.2s Lin Bytes test with Domain (shrinking:  190.0008)
[✓]   86    0    1   85 / 1000  4552.0s Lin Bytes test with Domain

[ ]    0    0    0    0 /  250     0.0s Lin Bytes test with Thread
Error: The operation was canceled.

That's 1h 14 min ~ 74min ((4552.0 -. 62.4) /. 60.) spent reducing a counterexample.

It is again on Cygwin - and very similar to #514, which may indicate a Cygwin issue rather than a Lin shrinking issue...

[jmid]

There may be an issue with pthreads in Cygwin.

On the merge to main of #519 for the Cygwin 5.3 workflow we just saw excessive time spent in Lin Bytes test with Thread
https://github.com/ocaml-multicore/multicoretests/actions/runs/12808801661/job/35712309410

random seed: 366364260
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 2500     0.0s Lin Bytes test with Domain
[ ]    0    0    0    0 / 2500     0.0s Lin Bytes test with Domain (generating)
[ ]   37    0    0   37 / 2500    60.2s Lin Bytes test with Domain (shrinking:   15.0003)
[ ]   37    0    0   37 / 2500   122.0s Lin Bytes test with Domain (shrinking:   18.0006)
[ ]   37    0    0   37 / 2500   182.5s Lin Bytes test with Domain (shrinking:   20.0008)
[ ]   37    0    0   37 / 2500   245.1s Lin Bytes test with Domain (shrinking:   23.0005)
[ ]   37    0    0   37 / 2500   308.1s Lin Bytes test with Domain (shrinking:   25.0002)
[ ]   37    0    0   37 / 2500   371.9s Lin Bytes test with Domain (shrinking:   28.0010)
[ ]   37    0    0   37 / 2500   433.4s Lin Bytes test with Domain (shrinking:   30.0013)
[ ]   37    0    0   37 / 2500   493.5s Lin Bytes test with Domain (shrinking:   32.0012)
[ ]   37    0    0   37 / 2500   556.0s Lin Bytes test with Domain (shrinking:   34.0002)
[ ]   37    0    0   37 / 2500   617.4s Lin Bytes test with Domain (shrinking:   35.0012)
[ ]   37    0    0   37 / 2500   677.9s Lin Bytes test with Domain (shrinking:   36.0015)
[ ]   37    0    0   37 / 2500   741.5s Lin Bytes test with Domain (shrinking:   37.0013)
[ ]   37    0    0   37 / 2500   806.4s Lin Bytes test with Domain (shrinking:   39.0004)
[ ]   37    0    0   37 / 2500   866.8s Lin Bytes test with Domain (shrinking:   40)
[ ]   37    0    0   37 / 2500   927.3s Lin Bytes test with Domain (shrinking:   41.0003)
[✓]   38    0    1   37 / 2500   984.5s Lin Bytes test with Domain

[ ]    0    0    0    0 /  250     0.0s Lin Bytes test with Thread
[ ]    3    0    0    3 /  250  1481.8s Lin Bytes test with Thread
[ ]    4    0    0    4 /  250  8943.0s Lin Bytes test with Thread (collecting)
Error: The operation was canceled.

That's 149min ~ 2h 29min to test 4 random inputs on the Thread variant? 🤔

[jmid]

This happened again in #521 on Cygwin trunk
https://github.com/ocaml-multicore/multicoretests/actions/runs/12810674241/job/35718270726?pr=521

random seed: 389881736
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 2500     0.0s Lin Bytes test with Domain
[ ]    0    0    0    0 / 2500     0.0s Lin Bytes test with Domain (generating)
[ ]  151    0    0  151 / 2500    60.0s Lin Bytes test with Domain (shrinking:   36.0011)
[ ]  151    0    0  151 / 2500   120.3s Lin Bytes test with Domain (shrinking:   40.0010)
[ ]  151    0    0  151 / 2500   184.0s Lin Bytes test with Domain (shrinking:   42.0015)

[...]

[ ]  151    0    0  151 / 2500 10444.5s Lin Bytes test with Domain (shrinking:  158.0007)
[ ]  151    0    0  151 / 2500 10540.1s Lin Bytes test with Domain (shrinking:  158.0008)
[ ]  151    0    0  151 / 2500 10633.5s Lin Bytes test with Domain (shrinking:  158.0009)
Error: The operation was canceled.

Timing out after 10633.5s!

[jmid]

I opened #526 to track occurrences of Lin Bytes test with Thread timeouts seperately.

[jmid]

On 9621d6d pushed to main in connection with the 0.7 release I observed this again on Cygwin trunk:
https://github.com/ocaml-multicore/multicoretests/actions/runs/12891457981/job/35943437614

random seed: 237443094
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 5000     0.0s Lin Bytes test with Domain
[ ]    0    0    0    0 / 5000     0.0s Lin Bytes test with Domain (generating)
[ ]   35    0    0   35 / 5000    60.6s Lin Bytes test with Domain (shrinking:   22.0013)
[ ]   35    0    0   35 / 5000   122.6s Lin Bytes test with Domain (shrinking:   26.0005)
[ ]   35    0    0   35 / 5000   183.5s Lin Bytes test with Domain (shrinking:   27.0010)

[...]

[ ]   35    0    0   35 / 5000  6985.6s Lin Bytes test with Domain (shrinking:   57.0054)
[ ]   35    0    0   35 / 5000  7071.8s Lin Bytes test with Domain (shrinking:   57.0060)
[ ]   35    0    0   35 / 5000  7143.7s Lin Bytes test with Domain (shrinking:   58.0004)
[ ]   35    0    0   35 / 5000  7216.1s Lin Bytes test with Domain (shrinking:   58.0006)
[ ]   35    0    0   35 / 5000  7288.9s Lin Bytes test with Domain (shrinking:   58.0014)
Error: The operation was canceled.