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
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