[SciPy-Dev] Doc error in scipy.optimize.fmin and missing info in ref guide

josef.pktd@gmai... josef.pktd@gmai...
Fri Mar 19 15:09:57 CDT 2010


On Fri, Mar 19, 2010 at 4:05 PM, David Goldsmith
<d.l.goldsmith@gmail.com> wrote:
> On Fri, Mar 19, 2010 at 12:37 PM,  <josef.pktd@gmail.com> wrote:
>> On Fri, Mar 19, 2010 at 3:16 PM, David Goldsmith
>> <d.l.goldsmith@gmail.com> wrote:
>>> On Mon, Mar 15, 2010 at 4:05 PM, Rob Clewley <rob.clewley@gmail.com> wrote:
>>>> Hi,
>>>>
>>>> In both my old version and the one in the svn trunk there is an
>>>> inconsistency in the docstring of scipy.optimize.fmin.
>>>>
>>>>    Other Parameters
>>>>    ----------------
>>>>    xtol : float
>>>>        Relative error in xopt acceptable for convergence.
>>>>    ftol : number
>>>>        Relative error in func(xopt) acceptable for convergence.
>>>>
>>>> As you see from the following code snippet from the body of the
>>>> function, the convergence test is in terms of absolute error for both
>>>> x and f, as the sim array contains x values and fsim the function
>>>> values.
>>>>
>>>>    if (max(numpy.ravel(abs(sim[1:]-sim[0]))) <= xtol \
>>>>                and max(abs(fsim[0]-fsim[1:])) <= ftol):
>>>>        break
>>>
>>> OK, folks, so what's the _desired_ behavior: absolute or relative
>>> error (i.e., where's the bug: in the code or in the doc)?
>>
>> I think the docs should reflect the actual behavior of the function.
>> Whether the criteria will be changed and made consistent across
>> functions is a different question. But it's not a bug, so the docs
>> should adjust.
>>
>> my opinion
>>
>> Josef
>
> Well, I'm pretty sure we formally adopted the opposite policy: the
> docs should reflect _desired_ behavior - if the code doesn't implement
> desired behavior then a bug report is to be filed.  (I thought this
> was in the Wiki Q&A section, but apparently not, so, UIAM, it's "only"
> in an email thread somewhere).  Can anyone else confirm and,
> hopefully, supply a link to the email thread in which this was
> discussed?

I know of that policy, but there are a lot of mistakes in the docs,
and I don't think we change the code to match the mistakes in the
docs.

But you can also file a ticket for changing and reviewing convergence criteria

I don't think relative (to what?) error makes much sense if x or f goes to zero.

Josef


>
> DG
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