8

What are the Method options Solve command accepts? Solve has the Method option, however documentation contains no methods that it accepts...

8

What are the Method options Solve command accepts? Solve has the Method option, however documentation contains no methods that it accepts...

5

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.

4

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]}}`

@Öskå. From my reading of the documentation, I conclude `Reduce`

and `Automatic`

are the only method choices available. So I think this a valid answer. – m_goldberg – 2014-05-13T10:30:39.037

@m_goldberg Although it would be "great" to have a function giving the available method for `Solve`

or `NDSolve`

or any function taking `Method`

as `Options`

. But you are right, in the case of `Solve`

it might be the only ones. – Öskå – 2014-05-13T10:36:27.760

Related: http://mathematica.stackexchange.com/q/809/131

– Yves Klett – 2014-05-13T10:15:37.793The documentation for

`Solve`

mentions that`Method -> Reduce`

can be given in place of`Method -> Automatic`

. It is implied, but not explicitly stated, that these are the only methods available. – m_goldberg – 2014-05-13T10:35:24.987