Using Fortran 90 and CTT
The document IMSL Computational Technology Toolkit contains an overview of CTT and information on its use that should be read prior to reading this document. The discussion below assumes that you have configured your UNIX account as described in that document.
Fortran 90 is designed for scientific programming projects. In contrast to Fortran 77, Fortran 90 includes new functions such as matrix intrinsic functions, low-level functions which formerly needed to be included in older IMSL Fortran 77 subprogram libraries.
The CTT modules for Fortran 90 evolved from the older IMSL subroutines. A single module accommodates all numerical precisions, includes parameter-type checking, and is therefore more versatile and easier to use. These module extensions are invoked via a Fortran 90 use statement. Unfortunately, VNI Inc. has not yet converted all of the earlier IMSL routines into Fortran 90 modules. So, it sometimes necessary to use the older subroutines, which now form the Fortran Numerical Library (FNL).
When starting a new project, you should first examine the CTT example program directory, $CTT_EXAMPLES/f90/manual, to see if you can find an appropriate Fortran 90 MP module to use. If that fails, you should look at the FNL choices. The documents Fortran 90 MP Example and Fortran 90 FNL Example give an annotated example of the use of a Fortran 90 CTT module and an FNL routine.