What are the Method options Solve command accepts? Solve has the Method option, however documentation contains no methods that it accepts...
2 Answers
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Undocumented Method->"Legacy" option forces Solve in version 8 to use algorithm from versions <=7.
exprs = Together[{(b + d + f)/x - (a + b)/(1 + x) -
2*(c + d + e)/(1 + 2*x + y) - (f + g)/(x + y), (e + g)/
y - (c + d + e)/(1 + 2*x + y) - (f + g)/(x + y)}];
Timing[solns1 = Solve[exprs == 0, {x, y}, Method -> "Legacy"];]
{39.515, Null}
Solve[exprs == 0, {x, y}] never returns in version 8. Additional examples see here.
Some information on the change in the algorithm between versions 7 and 8 is published by Bruce Miller (Wolfram Technical Support Group):
Boilerplate I had:
The difference between 7.0 and 8.0 output is that 7.0 Solve was treating equations that involved only variables as assumptions. This functionality was not precisely defined or consistently implemented and has been removed in 8.0. Instead there is a new option MaxExtraConditions which provides a well-defined and extended version of the functionality.
answered May 13, 2014 at 10:39
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2
With Method -> Reduce, Solve uses only equivalent transformations and finds all solutions.
Solve[x E^x == 1/2, x, Method -> Reduce]
{{x -> ConditionalExpression[ProductLog[C[1], 1/2], C[1] ∈ Integers]}}
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$\begingroup$ @Öskå. From my reading of the documentation, I conclude
ReduceandAutomaticare the only method choices available. So I think this a valid answer. $\endgroup$ May 13, 2014 at 10:30 -
$\begingroup$ @m_goldberg Although it would be "great" to have a function giving the available method for
SolveorNDSolveor any function takingMethodasOptions. But you are right, in the case ofSolveit might be the only ones. $\endgroup$– ÖskåMay 13, 2014 at 10:36
Solvementions thatMethod -> Reducecan be given in place ofMethod -> Automatic. It is implied, but not explicitly stated, that these are the only methods available. $\endgroup$