FRIDAY, JUNE 5, 2026
libstdc++
libstdc++: Fix Cylindrical Bessel functions for infinity.
Correctly returns zero for cylindrical Bessel functions at infinity.
The asymptotic approximation for cylindrical Bessel functions (__cyl_bessel_jn_asymp) in libstdc++ now correctly returns zero when the input x is infinite. This aligns the behavior with the expected mathematical limit and includes new test cases to verify this fix.
In Details
The asymptotic behavior of the __cyl_bessel_jn_asymp function, used for approximating cylindrical Bessel functions for large arguments, was incorrect. This commit adjusts the implementation to return 0.0 when x approaches infinity, a change motivated by PR119143 and verified with new testsuite entries.
For Context
- libstdc++
- The C++ standard library implementation used by GCC. It provides fundamental types and algorithms, including mathematical functions.
- Cylindrical Bessel functions
- A class of solutions to Bessel's differential equation, often used in physics and engineering to describe wave phenomena and other problems with cylindrical symmetry.
- asymptotic approximation
- A mathematical approximation that becomes increasingly accurate as the input variable approaches a specific limit (e.g., infinity).