Opened 11 years ago

Last modified 5 years ago

#3732 new enhancement

Unnecessary Maxima interactions in integration

Reported by: was Owned by: gfurnish
Priority: major Milestone: sage-6.4
Component: calculus Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description (last modified by kcrisman)

Here are a variety of integrals for which Maxima should not have to interact to ask about assumptions, but does.

Attachments (2)

testintfailscases.py (3.4 KB) - added by was 11 years ago.
gaussian-integral-testcase.py (487 bytes) - added by gnprice 10 years ago.
another failing integral

Download all attachments as: .zip

Change History (12)

Changed 11 years ago by was

comment:1 Changed 10 years ago by aginiewicz

There's another example (that's with 3.1.2.alpha2), here it shouldn't need assumption on a:

sage: var('a')
a
sage: integrate((x-a)^2*exp(-(x-a)^2), x, -Infinity, +Infinity)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/home/giniu/<ipython console> in <module>()

/opt/sage/local/lib/python2.5/site-packages/sage/calculus/functional.py in integral(f, *args, **kwds)
    252     """
    253     try:
--> 254         return f.integral(*args, **kwds)
    255     except ValueError, err:
    256         raise err

/opt/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.py in integral(self, v, a, b)
   2532                     raise ValueError, "Integral is divergent."
   2533                 else:
-> 2534                     raise TypeError, error
   2535                     
   2536 

TypeError: Computation failed since Maxima requested additional constraints (use assume):
Is  a  positive or negative?

Changed 10 years ago by gnprice

another failing integral

comment:2 Changed 10 years ago by gnprice

I added a testcase for another integral, namely integral( s^2 * exp(- (a + b) * s^2 ), s), that fails to integrate. This is reproduced on Sage 3.1.1.

comment:3 Changed 10 years ago by kcrisman

  • Summary changed from calculus -- some examples of sage integration failing to Additional examples of maxima interactions in calculus leading to errors

Added clearer summary. The second attachment is not relevant to this ticket, though certainly we should be able to integrate arbitrary functions!

What is the purpose of this ticket long-term? These could be added, complete with their error messages, to calculus.py examples - but we already have several of those. Or one could say this is just a reminder of what we would eventually like Sage to be able to use Maxima to do, and put them in but not test them.

Otherwise this is in some sense related to solving #780 (among several others), which is a thornier problem.

comment:4 Changed 9 years ago by kcrisman

With the latest Maxima upgrade and Pynac conversion, the last two integrals are correct - the penultimate one is, of course,

1/2*sqrt(pi)

and the last one is

1/2*(a+b)^(3/2)*s^3*gamma_incomplete(-3/2,(a+b)/s^2)/(s^2)^(3/2)

comment:5 Changed 9 years ago by kcrisman

  • Description modified (diff)
  • Summary changed from Additional examples of maxima interactions in calculus leading to errors to Unnecessary Maxima interactions in integration

Here is the current state of this ticket. Of the examples in the first attached file, the following are legitimate bugs of this type.

The first example has unnecessary questions.

sage: integrate(1/sqrt(x-q), x, 1, 2)
2 sqrt(2 - q) - 2 sqrt(1 - q) # should be this always

The third example is definitely a case for this, as of Maxima 5.19.1:

(%i19) integrate(log(q-x), x, a, b);
Is  b - a  positive, negative, or zero?

positive;
(%o19)          (b - q) log(q - b) - (a - q) log(q - a) - b + a
(%i20) integrate(log(q-x), x, a, b);
Is  b - a  positive, negative, or zero?

negative;
(%o20)          (b - q) log(q - b) - (a - q) log(q - a) - b + a
(%i21) integrate(log(q-x), x, a, b);
Is  b - a  positive, negative, or zero?

zero;
(%o21)          (b - q) log(q - b) - (a - q) log(q - a) - b + a

The fifth example has MANY questions to ask, always the same answer:

(%i36) integrate(1/sqrt(q^2-x^2),x, a, b);
Is  b - a  positive, negative, or zero?

negative;
Is  q - a  positive, negative, or zero?

zero;
Is  q + a  positive, negative, or zero?

zero;
Is  q + b  positive, negative, or zero?

positive;
                                 b              a
(%o36)                    asin(------) - asin(------)
                               abs(q)         abs(q)

++++++++++++++++++++++++++++++++

The following should not be considered bugs, at least not for the reason given.

The second example is okay:

sage: integrate(1/(x-q),x,1,2)

Maxima adds pi*I and/or switches q-2 to 2-q as appropriate. If we don't like those differences, that should be on a different ticket.

The fourth example is:

sage: integrate(1/(q-x^2), x)

The answers given are a constant away from each other, but look very different. This probably should be considered a bug (Maxima can't connect between logs and arctan/h stuff), but is likely to not be resolved soon, or by questions.

The last example is definitely not a bug, as for q=-1 you should get a different answer!

comment:6 Changed 9 years ago by kcrisman

  • Report Upstream set to N/A

Update: these (the three remaining ones above) are still in Maxima 5.20.1.

comment:7 Changed 6 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:8 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.1 to sage-6.2

comment:9 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.2 to sage-6.3

comment:10 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.3 to sage-6.4
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