The prompts given to ChatGPT-4 are shown in the codes. Sometimes cleanup was required. This is an experiment in code generation by ChatGPT -- the codes should not be relied upon.
Compile with
gfortran optim_util.f90 adam.f90 nelder_mead.f90 conjugate_gradient_min.f90 bfgs_min.f90 luus_jaakola.f90 gradient_descent.f90 xminimize.f90
Works with gfortran 12.0.1 20220213 and ifort version 2021.6.0.
When ChatGPT-4 generates code, it often forgets the import statement that is needed in the interface below.
interface
function funk(x)
import :: dp
real(kind=dp), dimension(:), intent(in) :: x
real(kind=dp) :: funk
end function funk
end interface`
It can produce code with implicit none and undeclared variables that does not compile. It tends to declare a variable i as integer even in a procedure that does not use the variable i.
When ChatGPT-4 translated some algorithms from the literature with g*g' or equivalently g*transpose(g), it erroneously translated this to g**2 in Fortran instead of sum(g**2).