Thanks for the reply. That's disappointing—I'm not crazy about the idea of
spawning a hundred million Sage processes, most of them to do about 1/50th
of a second's worth of calculation, just because a few of them will need to
be timed out before they take hours or days or run out of memory. I'm
finding ways to work around it and still work within a Jupyter worksheet,
but I guess that means I'll have to verify any results I really care about
in their own standalone session, if every interruption is considered to
transform Sage into unreliable software as a fact of life.
Is there any sort of a command that I can run after interrupting a Groebner
basis calculation that will purge the Singular state, that will clear
whatever intermediate results Singular seems to be keeping in memory after
an interruption?
If anyone is curious to see an example of the sort of behavior I was
talking about, the following sequence seems to trip the error in a fairly
reproducible way (for example, I got it to work on the CoCalc server).
Notice that at the end the same calculation repeated three times results in
different behavior each time, with the first one giving a runtime error.
----------------------------------------------------------------
sage: P = PolynomialRing(QQ, ['a' + str(ii) for ii in range(8)])
sage: P.inject_variables()
Defining a0, a1, a2, a3, a4, a5, a6, a7
sage: anideal = ideal(-a0*a2*a4 + a0*a4*a5,
....: -a2*a4 + a4*a5,
....: a0*a2*a3*a7 - a0*a1*a4,
....: a0*a2*a3 + a0*a2*a7 + a2*a3*a7 - a0*a4 - a1*a4 -
a3*a6,
....: a0*a1*a3*a7 + a0*a2 + a2*a3 + a2*a7 - a4 - a6,
....: a0*a1*a3 + a0*a1*a7 + a0*a3*a7 + a1*a3*a7 + a2,
....: a0*a1 + a0*a3 + a1*a3 + a0*a7 + a1*a7 + a3*a7,
....: a0 + a1 + a3 + a7 - 1)
sage: for ii in range(1):
....: alarm(10)
....: try:
....: if prod(P.gens())^2 in anideal:
....: cancel_alarm()
....: print('Success: True.')
....: break
....: else:
....: cancel_alarm()
....: print('Success: False.')
....: break
....: except AlarmInterrupt:
....: print('Timeout.')
....: break
....:
Timeout.
sage: P = PolynomialRing(QQ, ['w', 'y', 'z'])
sage: P.inject_variables()
Defining w, y, z
sage: anideal = ideal(w^20*y^10, z^5)
sage: anideal.radical()
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-9-1b5ff2b0d4f2> in <module>()
----> 1 anideal.radical()
/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/rings/polynomial/multi_polynomial_ideal.pyc
in __call__(self, *args, **kwds)
295 if not R.base_ring().is_field():
296 raise ValueError("Coefficient ring must be a field for
function '%s'."%(self.f.__name__))
--> 297 return self.f(self._instance, *args, **kwds)
298
299 require_field = RequireField
/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/libs/singular/standard_options.pyc
in wrapper(*args, **kwds)
138 """
139 with LibSingularGBDefaultContext():
--> 140 return func(*args, **kwds)
141 return wrapper
/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/rings/polynomial/multi_polynomial_ideal.pyc
in radical(self)
1636 import sage.libs.singular.function_factory
1637 radical =
sage.libs.singular.function_factory.ff.primdec__lib.radical
-> 1638 r = radical(self)
1639
1640 S = self.ring()
/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/libs/singular/function.pyx
in sage.libs.singular.function.SingularFunction.__call__
(build/cythonized/sage/libs/singular/function.cpp:15056)()
1328 if not (isinstance(ring, MPolynomialRing_libsingular) or
isinstance(ring, NCPolynomialRing_plural)):
1329 raise TypeError("Cannot call Singular function '%s'
with ring parameter of type '%s'"%(self._name,type(ring)))
-> 1330 return call_function(self, args, ring, interruptible,
attributes)
1331
1332 def _instancedoc_(self):
/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/libs/singular/function.pyx
in sage.libs.singular.function.call_function
(build/cythonized/sage/libs/singular/function.cpp:17032)()
1526 if errorreported:
1527 errorreported = 0
-> 1528 raise RuntimeError("error in Singular function call
%r:\n%s" %
1529 (self._name, "\n".join(error_messages)))
1530
RuntimeError: error in Singular function call 'radical':
no ring active
sage: anideal.radical()
// ** redefining i (parameter ideal i; parameter list #; )
// ** redefining Pl ( list Pl=ringlist(P0);)
Ideal (z, w*y) of Multivariate Polynomial Ring in w, y, z over Rational
Field
sage: anideal.radical()
Ideal (z, w*y) of Multivariate Polynomial Ring in w, y, z over Rational
Field
On Monday, May 27, 2019 at 10:08:34 AM UTC-6, Jeroen Demeyer wrote:
>
> On 2019-05-27 16:11, Tracy Hall wrote:
> > in particular it seems to have undefined
> > behavior in subsequent calls after it has been interrupted by alarm().
>
> This is simply a fact of life and not really considered to be a bug. You
> should not rely on the fact that interruptions (using either CTRL-C or
> alarm) work perfectly. Don't use alarm() for serious computations.
>
> If you need proper timeouts, one thing you can do is spawn multiple Sage
> processes or fork one Sage process. Then you can kill the whole process
> after a certain amount of time.
>
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