Status: Accepted
Owner: asmeurer
Labels: Type-Defect Priority-Medium Solvers EasyToFix
New issue 2235 by asmeurer: Default order of hints to dsolve()
http://code.google.com/p/sympy/issues/detail?id=2235
The default order of hints to dsolve() is given by the allhints variable in
ode.py. Here is an excerpt from the code:
# This is a list of hints in the order that they should be applied. That
means
# that, in general, hints earlier in the list should produce simpler results
# than those later for ODEs that fit both. This is just based on my own
# empirical observations, so if you find that *in general*, a hint later in
# the list is better than one before it, fell free to modify the list. Note
# however that you can easily override the hint used in dsolve() for a
specific ODE
# (see the docstring). In general, "_Integral" hints should be grouped
# at the end of the list, unless there is a method that returns an
unevaluatable
# integral most of the time (which should surely go near the end of the list
# anyway).
# "default", "all", "best", and "all_Integral" meta-hints should not be
# included in this list, but "_best" and "_Integral" hints should be
included.
allhints = ("separable", "1st_exact", "1st_linear", "Bernoulli",
"1st_homogeneous_coeff_best", "1st_homogeneous_coeff_subs_indep_div_dep",
"1st_homogeneous_coeff_subs_dep_div_indep",
"nth_linear_constant_coeff_homogeneous",
"nth_linear_constant_coeff_undetermined_coefficients",
"nth_linear_constant_coeff_variation_of_parameters",
"Liouville", "separable_Integral", "1st_exact_Integral", "1st_linear_Integral",
"Bernoulli_Integral", "1st_homogeneous_coeff_subs_indep_div_dep_Integral",
"1st_homogeneous_coeff_subs_dep_div_indep_Integral",
"nth_linear_constant_coeff_variation_of_parameters_Integral",
"Liouville_Integral")
I think the 1st_linear and Bernoulli hints should come before separable and
1st_exact, since they always return solution that are solved for f(x).
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