GNU Scientific Library - Bugs: bug #45053, gsl_min_find_bracket is most...
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bug #45053: gsl_min_find_bracket is most likely incorrectly implemented
Submitter: | Chris Mansley <cmansley> | ||
Submitted: | Thu 07 May 2015 11:26:20 PM UTC | ||
Category: | Runtime error | Severity: | 3 - Normal |
Operating System: | ubuntu 12.04 (kernel 3.8.0-44-generic) | Status: | None |
Assigned to: | None | Open/Closed: | Open |
Release: | 1.15 |
Attached Files
Depends on the following items: None found
Items that depend on this one: None found
Carbon-Copy List
Follow 2 latest changes.
Date | Changed by | Updated Field | Previous Value | => | Replaced by |
---|---|---|---|---|---|
2015-05-07 | cmansley | Attached File | - | ![]() |
Added gsl_bug.c, #33962 |
Attached File | - | ![]() |
Added bracketing.patch, #33963 |
There is a function for pre-bracketing the minimum for the gsl_min_fminimizer_* set of functions called gsl_min_find_bracket. This function can be forced to evaluate the function outside of the initial supplied bracket.
This is extremely bad as the function may not be defined outside of the initial range.
The attached program, gsl_bug.c, forces the bracketing to search outside of the initial range on a parabola, which should be a simple bracketing operation.
The attached patch follows the formulations formulations of bracketing from Brent's algorithm and the golden area search, by reducing the bracket area at each step.
In gsl_bug.c, the patched function performs a better bracketing with fewer iterations.
I did not exhaustively test this for failure cases, but it seems like it does a better job fulfilling the specifications.
I would like to hear if this was intended behavior or an actual bug.