软件说明.txt

是一个接收永磁体磁场计算的程序

MAIN is the main program for FD2D. 
DS3_DIAGONAL2 reorders two square DS3 matrices so diagonal entries are first. 
DS3_JAC_SL solves a DS3 system using Jacobi iteration. 
I4_SWAP swaps two I4's. 
I4VEC2_SORT_A_PLUS2 ascending sorts integer pairs, and adjusts real vectors. 
MATVEC_TRIAD computes A*X for a matrix A stored in SLAP Triad form. 
MSOLVE_IDENTITY applies the identity matrix preconditioner. 
R8_SWAP swaps two R8's. 
SPARSE manages the storage of sparse matrix information. 
SORT_HEAP_EXTERNAL externally sorts a list of items into ascending order.




FD2D is a FORTRAN90 program, using double precision arithmetic, which solves a predator-prey system in a two dimensional region. The program requires both some interactive input from the user, and two simple FORTRAN90 routines that define the initial values. 

The nondimensional problem has the form 

        du/dt =         del u + ( 1 - u ) * u        - v * h(u/alpha)

        dv/dt = delta * del v     - gamma * v + beta * v * h(u/alpha)
      
in a square [A,B]x[A,B], with initial conditions: 
        u(x,y,0) = u0(x,y)
        v(x,y,0) = v0(x,y)
      
and Neumann boundary conditions along the boundary of the square: 
        du/dn = 0
        dv/dn = 0
      
The Type II functional response employed here is 
        h(eta) = eta / ( 1 + eta )
      
The parameters ALPHA, BETA, GAMMA and DELTA are strictly positive. 

The user must input a value H specifying the desired space step to be used in discretizing the space dimension. 

A finite difference scheme is employed to integrate the problem from time 0 to a maximum time T. The user must input the value T, as well as an appropriate time step DELT. 

A typical input for this problem is: 

        ALPHA =   0.4
        BETA  =   2.0
        GAMMA =   0.6
        DELTA =  10.0
        A     =   0.0
        B     = 500.0
        H     =   1.0
        T     = 150.0
        DELT  =   0.041666666666666
        SOLVE =   0
      
with the following initial values of U and V supplied in auxiliary subroutines: 
        ustar = gamma * alpha / ( beta - gamma )

        u0(i,j) = ustar - 2.0E-07 * ( x(i,j) - 0.1 * y(i,j) - 225.0 ) 
          * ( x(i,j) - 0.1 * y(i,j) - 675.0 )

        vstar = ( 1.0 - ustar ) * ( alpha + ustar )

        v0(i,j) = vstar - 3.0E-05 * ( x(i,j) - 450.0 ) 
          - 1.2E-04 * ( y(i,j) - 150.0 )