URL: <https://savannah.gnu.org/bugs/?68068>
Summary: Bug: incorrect straddling of area of convergence in
quad_golden
Group: GNU Scientific Library
Submitter: fermelelundi
Submitted: Thu 19 Feb 2026 02:20:14 PM UTC
Category: Accuracy problem
Severity: 3 - Normal
Priority: 5 - Normal
Operating System:
Status: None
Assigned to: None
Open/Closed: Open
Discussion Lock: Unlocked
Release: 2.8
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Follow-up Comments:
-------------------------------------------------------
Date: Thu 19 Feb 2026 02:20:14 PM UTC By: Fermé le Lundi <fermelelundi>
In file min/quad_golden.c there is a function quad_golden_iterate with the
following:
/* Update {x,f}_lower, {x,f}_upper, {x,f}_prev_small, {x,f}_small, and
{x,f}_minimum */
if (f_eval <= f_m)
{
if (x_eval < x_m)
{
*x_upper = x_m;
*f_upper = f_m;
}
else
{
*x_lower = x_m;
*f_upper = f_m;
}
The latter assignment should probably be *f_lower = f_m;
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