I see several problems with the __fls function: - You can't use "__" in your own identifiers; such names are reserved. - The implementation uses x86 assembly. - The unsigned long -> int typecast looks redundant to me. Typo in src/optimize/lbfgs.f: THE THE -> THE. Typo in src/optimize/lbfgsb.f: easible -> feasible. -- Jakub Wilk