Updates:
Status: Started
Blockedon: 2043
Comment #3 on issue 2113 by asmeurer: integrate(cos(log(x**2))/x) hangs
http://code.google.com/p/sympy/issues/detail?id=2113
Interesting. I bisected, and it looks like this commit fixes it:
commit eda08779c7a1b3fe7a97854c3436075c901bd56b
Author: Chris Smith <[email protected]>
Date: Mon Aug 23 12:32:40 2010 +0545
2043 exp and log handling changed
log(exp(x)) == log(x) so I deleted the comment about the omitted test.
The condition on expanding log(x**y) was changed to the include the
test for x being positive. The nseries test passes when x is given
the positive=True assumption.
It can now be tested if one expression is an integral power of another,
e.g. cancel(log(4*pos**2/9, 2*pos/3)) -> 2
log(Rational) is no longer expanded except for perfect bases, so
log(16).expand() -> 4*log(2)
log(12).expand() -> log(12)
log(3/5).expand() -> log(3/5)
log((3/5)**2) -> 2*log(3/5)
When trying to prove expressions are equal that involve logs of
rationals, try logcombine; it's cheaper to collect logs than to
factor ints and separate them into logs:
>>> log(18)-(log(2)+2*log(3))
-log(2) - 2*log(3) + log(18)
>>> logcombine(_)
0
So probably somewhere in there it is able to handle log(x**2) == 2*log(x)
better than before.
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