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 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 in Chapter 1, “Linear
Systems” of
lin_sol_gen
for an example of computing the inverse matrix.
For compatibility with previous versions of the IMSL Libraries, the NUMERICAL_LIBRARIES interface module includes backwards-compatible positional argument interfaces to all routines that existed in the Fortran 77 version of the Library. Note that it is not necessary to include “use” statements when calling these routines by themselves. Existing programs that called these routines will continue to work in the same manner as before.
Some of the primary routines have arguments “epack=” and “iopt=”. As noted the “epack=” argument is of derived type s_error or d_error. The prefix “s_” or “d_” is chosen depending on the precision of the data type for that routine. These optional arguments are part of the interface to certain routines, and are used to modify internal algorithm choices or other parameters.
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