fsolve with external fortran subroutine

[Eduardo Torrecillas]

Hi everybody,

I am trying to use fsolve with a fortran subroutine as argument. For
example, consider the following calling sequence:

X0=[0 0]

tol=1E-15

[X,v]=fsolve(X0,'fequil_fortran',tol)



In this case 'fequil_fortran' is my external fortran subroutine, given
below:

--------------------------------------------------------------------

subroutine fequil_fortran(n,x,v,iflag)

implicit none

integer,intent(in)::n,iflag

real(kind=8),dimension(n),intent(in)::x

real(kind=8),dimension(n),intent(out)::vreal(kind=8)::a,b

 a=1.0_dp

b=2.0_dp

v(1)=a*x(1)+b*x(2)-1.0_dp

v(2)=2.0_dp*a*x(1)-b*x(2)-5.0_dp

end subroutine fequil_fortran

---------------------------------------------------------------------

It worked fine and fsolve found the solution. Now, suppose I have to pass
arguments to the fortran subroutine, in addition to the default
(n,x,v,iflag). For instance, imagine I had to pass the 'a' and 'b'
variables from Scilab to the fortran subroutine in the code above. I have
already performed something like this but with "optim". In fact, "optim"
gives you the possibility to pass a list of integer, real or double
variables to the external code. Is there anything similar to be used with
fsolve?
Regards,

-- 
Eduardo Torrecillas
AER-09
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