Installation Guide

This package is written in 1977 ANSI standard FORTRAN in the interests of portability. However, the following changes to the code should be considered when transporting the code to another computer.

1.

This version of ITPACK was written to be efficient on vector computers having a vector cache or vector registers and whose compilers can vectorize gather/scatter programming constructs. For maximum efficiency on Cray vector computers, the FORTRAN routines ISMIN(), WHENIGE(), WHENILT(), SAXPY(), SCOPY(), SDOT(), and SNRM2() should be deleted from the package since optimized CAL versions of these routines exist. Also, in routine DETERM(), loop 10 should be deleted and the line containing the call to SOLRN() should be activated.

2.

The timing routine TIMER() uses the routine SECOND(). Since there is no standard timing routine in FORTRAN, this subroutine may have to be modified. Also, many computers have more accurate timing facilities than SECOND().

3.

The value of the machine relative precision is contained in the variable SRELPR, which is set in the DFAULT() subroutine. This and other default values may be permanently changed when the code is installed by changing their values in this subroutine. In particular, SRELPR must be changed for different computers. If the installer of this package does not know its value, an approximate value can be determined from a simple FORTRAN program given in the comment statements of subroutine DFAULT().

4.

Since the amount of precision may change from computer to computer, the relative accuracy requested in the stopping criterion ZETA must not be less than about 500 times the machine relative precision SRELPR. If a value of ZETA is requested that is too small, then the code resets it to this value. The current default value for ZETA, $5 \times 10^{-6}$, is set by the routine DFAULT() into RPARM(1).

5.

The program line of the ITPACKV testing program may need to be changed since different computers have different conventions for opening files.

The testing program and the routines DFAULT() and TIMER() are the only routines which require editing by the installer of the package. It is suggested that ITPACKV be made into a compiled program library although not all of it would normally be used in a particular application.