@fork decorator with try/except on different platforms, not executing except clause

asked 2020-04-22 06:09:34 -0500

Rik gravatar image

I am having problems using the @fork decorator with a try & except clause. On SageMathCell the piece of code runs fine, whereas on both Jupyter and CoCalc it doesn't throw the exception clause properly. On CoCalc it didn't recognise the @fork decorator at all at first, but from sage.all import * (idea from question: "@fork decorator not recognized in script") seemed to help.

Piece of code:

from sage.all import * #for CoCalc

a_0,a_1 = var('a_0,a_1');s = [a_0,a_1]
equations = [69*a_0 + 4556 == 69*a_0 + 63*a_1, 69*a_1 - 3350 == -67*a_0 + 57*a_1, 63*a_0 - 3876 == -1542, 63*a_1 + 2850 == 7406]

try:
    @fork(timeout=0.1, verbose=True) #use e.g. 0.1 and 10
    def DirectSolution():
        sage_solution = solve(equations, s , solution_dict=True)
        print('Solves in time ,','sage_solution:',sage_solution)
        return sage_solution
    sage_solution = DirectSolution()[0]

except KeyboardInterrupt:
    sage_solution = []
    print('Takes too long , ','sage_solution:',sage_solution)

print('Execute the rest of the code, ','sage_solution:',sage_solution)

Running the @fork decorator without try/except with 0.1 seconds I got the KeyboardInterrupt error, that's why I used it in the except clause. Shouldn't this exception usually be "raised when the user hits the interrupt key" ?

  • As mentioned above, on SageMathCell the code works as intended:

    With 10 seconds it computes the solution and prints out the text. For 0.1 seconds it sets sage_solution = [] and prints out the text.

  • However, both on Jupyter and CoCalc it doesn't use the exception properly for 0.1 seconds. I get the following message:

    Killing subprocess 1346 with input ((), {}) which took too long

    Execute the rest of the code, sage_solution: N

    Meaning it didn't execute the except clause:

    sage_solution = []

    print('Takes too long , ','sage_solution:',sage_solution)

I am not sure what to look for here, because it is working on one platform. A simple try/except example worked fine. Another idea was that the KeyboardInterrupt could be the problem, but removing it didn't change anything.

I am new to Sage/Python, so there probably is a simple solution but I am happy for any help given. Unfortunately my karma was insufficient to publish links.

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