Issue 3845 in sympy: dsolve gives different answers

[sy...@googlecode.com]

Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 3845 by smi...@gmail.com: dsolve gives different answers
http://code.google.com/p/sympy/issues/detail?id=3845

in PR 1964 I worked around different forms of the solution of an ode that
are being returned. I didn't track down the source of the variability.

eq2 = (2*x*f(x) + 1)/f(x) + (f(x) - x)/f(x)**2*f(x).diff(x)
sol2 = Eq(f(x), C1*exp(-x**2 + LambertW(C2*x*exp(x**2))))
sol2b = Eq(log(f(x)) + x/f(x) + x**2, C1)
sol2c = Eq(f(x), exp(C1 - x**2 + LambertW(C2*x*exp(x**2))))
# XXX why is there more than one form coming back from this?
# sol2 comes back with PYTHONHASHSEED=3016992991
# sol2c comes back with PYTHONHASHSEED=7938055
assert dsolve(eq2, f(x), hint='1st_exact') in [sol2, sol2b, sol2c]


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[sy...@googlecode.com]

Updates:
Labels: NeedsReview smichr

Comment #1 on issue 3845 by smi...@gmail.com: dsolve gives different answers
http://code.google.com/p/sympy/issues/detail?id=3845

A serial replacement was being used in constsimp and I think that was the
source of the indeterminism. PR 1964 will show if this is the case or not.

[sy...@googlecode.com]

Updates:
Status: Fixed

Comment #2 on issue 3845 by smi...@gmail.com: dsolve gives different answers
http://code.google.com/p/sympy/issues/detail?id=3845

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