IMSL Fortran Numerical Library routines have
required arguments and may have
optional arguments. All arguments are documented for each routine. For example, consider the routine
lin_sol_gen that solves the linear algebraic matrix equation
Ax =
b. The required arguments are three rank-2 Fortran 90 arrays:
A,
b, and
x. The input data for the problem are the
A and
b arrays; the solution output is the
x array. Often there are other arguments for this linear solver that are closely connected with the computation but are not as compelling as the primary problem. The inverse matrix
A-1 may be needed as part of a larger application. To output this parameter, use the optional argument given by the “
ainv=” keyword. The rank-2 output array argument used on the right-hand side of the equal sign contains the inverse matrix. See
Example 2 of LIN_SOL_GEN in
Chapter 1, “Linear Systems” for an example of computing the inverse matrix.