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TimefoldAI / timefold-solver-python

Timefold Solver is an AI constraint solver for Python to optimize the Vehicle Routing Problem, Employee Rostering, Maintenance Scheduling, Task Assignment, School Timetabling, Cloud Optimization, Conference Scheduling, Job Shop Scheduling, Bin Packing and many more planning problems.
https://timefold.ai
Apache License 2.0
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python: hello-world / JavaException when using DEBUG log level #103

Closed Alex-K37 closed 5 days ago

Alex-K37 commented 1 week ago

Describe the bug

Turning on DEBUG logging causes exceptions with the hello-world example.

Expected behavior More detailed log messages.

Actual behavior

The following error is shown (only first few lines):

Traceback (most recent call last): File "DefaultSolver.java", line 200, in ai.timefold.solver.core.impl.solver.DefaultSolver.solve Exception: Java Exception

The above exception was the direct cause of the following exception:

Traceback (most recent call last): File "/home/***/.virtualenvs/timefold/lib/python3.11/site-packages/timefold/solver/_solver.py", line 109, in solve java_solution = self._delegate.solve(java_problem) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ai.timefold.jpyinterpreter.types.errors.ai.timefold.jpyinterpreter.types.errors.AttributeError: ai.timefold.jpyinterpreter.types.errors.AttributeError: object '08:30' does not have attribute 'strftime'

To Reproduce

diff --git a/python/hello-world/src/hello_world/main.py b/python/hello-world/src/hello_world/main.py index 660f7430..4b60fade 100644 --- a/python/hello-world/src/hello_world/main.py +++ b/python/hello-world/src/hello_world/main.py @@ -10,7 +10,7 @@ from .domain import * from .constraints import define_constraints

-logging.basicConfig(level=logging.INFO) +logging.basicConfig(level=logging.DEBUG) LOGGER = logging.getLogger('app')

Environment

Timefold Solver Version or Git ref:
1.11.0b0

Output of java -version: openjdk version "17.0.11" 2024-04-16 OpenJDK Runtime Environment (build 17.0.11+9-suse-150400.3.42.1-x8664) OpenJDK 64-Bit Server VM (build 17.0.11+9-suse-150400.3.42.1-x8664, mixed mode, sharing)

Output of uname -a or ver: Linux think14 5.14.21-150500.55.65-default TimefoldAI/timefold-solver#1 SMP PREEMPT_DYNAMIC Thu May 23 04:57:11 UTC 2024 (a46829d) x86_64 x86_64 x86_64 GNU/Linux

triceo commented 6 days ago

Thanks for reporting, @Alex-K37! We'll take a look when time permits.

Christopher-Chianelli commented 5 days ago

Caused by the issue this fixes: https://github.com/TimefoldAI/timefold-solver-python/pull/101 ; The gist of it is because Python datetime classes are C-Native, we need to implement our own to avoid FFI calls (that is, Python calling Java or Java calling Python). The datetime classes were missing a few methods that deal with formatting. The hello-world and school-timetabling examples used said unimplemented method in their __str__ function. The __str__ function is only called when DEBUG logging or lower is used.

If you modified the __str__ function of Timeslot to not call strftime, no exception would occur.