This program implements layers geomery.

Before compiling it, make sure that you compile the library with
dense matrix options (the default one).
To compile it, just type "make" and it will produce an executable "sheet".
If you want to use entire G_tau matrix to reduce the error bar,
compile with "make bigg".

To run it, type
  "./sheet < small.in"

The file "small.in" contains configurations for layes structure.
One should give
1. nx, ny, nz: the dimensions of x, y, z, where z is the number of layers.
2. U, mu, t: model parameters. note that U and mu should be given two numbers,
             while t should be given 3. The first two specify the parameters
             for each layer; the last is for inter-layer.
3. The rest are similar to the 2D lattice code.

The output will be dumped on screeen, which can be redicted to any files 
by 
	"./sheet < small.in > any_files"

The output contains most equal time measurement, except pair ones, and 
one unequal time measurement, which is

	A(layer_i, tau_j) = sum_{k} (G_up(layer_i, tau_k, site_k)+
				     G_dn(layer_i, tau_k, site_k))
 

The Green's function and other correlation functions are indexed by
four numbers (layer, dx, dy, dz)


Roger
4/1/08