[NUMBERS-168] BrentSolver cannot identify brackets with small objective values

• Type: Bug
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 1.0
• Fix Version/s: 1.1
• Component/s: rootfinder
• Assignee: Alex Herbert
• Reporter: Alex Herbert
• Created: 02/Oct/21 23:32
• Updated: 01/Nov/22 11:00
• Resolved: 02/Oct/21 23:39

Description

The BrentSolver detects a change in sign using:

if (x * y < 0) {

This does not work if the product is zero as is the case with sub-normal numbers. The sign of the zero can be compared using:

if (Double.compare(x * y, 0.0) < 0) {

This will detect -0.0 and allows the solver to search the bracket interval.