Linking external programs with the max-ent library

If one wants to use the max-ent library with any other program, then first create the static library file libmaxent.a by invoking make maxentlib in the top-directory. Let the environment variable MAXENTDIR point to where MAXENT-V1.4 is located. The library file is at $(MAXENTDIR)/MAXENT-V1.4/lib/libmaxent.a. To link this library file with any other Fortran 90 program, the following command can be used:

g95 -o a.out <object-files> -L $(MAXENTDIR)/MAXENT-V1.4/lib -lmaxent

If an interface from a C or C ++ program is required, the appropriate call (depending on the compiler and the operating system) should be invoked. The subroutine call from a Fortran 90 program to compute the max-ent basis functions is given below (see main.f90 and also maxent.f90 for further details):

call drivermaxent(n,nsd,scheme,prior,xyz,p,rmax,D,maxit,eps,printflag,errorflag,lengthscale,dettol,phi,dphi,ddphi)

The input parameters in the above subroutine are as follows:

1. n : number of neighbors of point $p$ (a positive integer);
2. nsd : spatial dimension (a positive integer);
3. scheme : either descent, newton, or lbfgs (a string);
4. prior : either uniform, cubic, quartic, gaussian, or gaussian-rbf (a string);
5. xyz : nodal coordinates of the $n$ neighbors (double precision array xyz(n,nsd));
6. p : coordinates of the point $p$ (double precision array p(nsd));
7. rmax : support sizes of the $n$ neighbors (double precision array rmax(n));
8. D : anisotropic metric (double precision array D(nsd,nsd,n));
9. maxit : maximum number of iteration (a positive integer);
10. eps : convergence tolerance (double precision);
11. printflag : print convergence information (logical: .true. or .false.);
12. errorflag : error flag ($0:$ pass, $1:$ Hessian too small; $2:$ non-convergence in maxit iterations);
13. lengthscale : length scale for domain (optional argument) so that convergence criterion is independent of the magnitude of nodal coordinates;
14. dettol : determinant tolerance (optional argument) with default of $10^{-16}$

The output variables (phi, dphi, and ddphi) in the parameter-list are defined as optional:

1. phi : basis function vector (double precision phi(n));
2. dphi : 1st derivatives of basis functions (double precision dphi(nsd,n));
3. ddphi : 2nd derivatives of basis functions (double precision ddphi(nsd*nsd,n));

Please note that any calling subroutine must first determine for every point $p$, the number of neighbors $n$ for $p$, assign the nodal coordinates of these $n$ nodes to the array xyz, and the support sizes of these $n$ nodes must be assigned to the array rmax. Then only can a call to the subroutine drivermaxent$(\ldots)$ be invoked. It is assumed that computations for dphi and/or ddphi are requested in conjunction with phi. Hence, in the parameter-list, phi ($\phi_i$ is computed), phi and dphi ($\phi_i$ and ${\nabla} \phi_i$ are computed), phi and ddphi ($\phi_i$ and ${\nabla} {\nabla} \phi_i$ are computed), or all three ($\phi_i$, ${\nabla} \phi_i$ and ${\nabla} {\nabla} \phi_i$ are computed) are valid.