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EXTEND.HLP -- Help file for EXTEND Version 7 February 1983
Routines for using large arrays from Fortran programs
Fortran programs can manipulate arrays containing more than 256K words
of data. Such arrays (called "large" arrays) cannot be declared local
to program units, or declared in COMMON blocks. They must be created
by a system subroutine named EXTEND and passed as arguments to all of
the subprograms that must manipulate them. To call a subroutine which
requires large arrays, you must call EXTEND with an argument list
which includes the name of your subroutine that you want to be invoked
with large arrays as arguments. EXTEND will create the arrays and
then call the subroutine. When that routine returns to EXTEND, the
arrays are discarded and control returns to the caller of EXTEND.
Before you can use large arrays, you have to initialize the subroutine
package. Do this by:
Also, if SORT is going to be called after the call to EXTINI, there
must be a CALL SORT(' ') before the call to EXTINI. This makes SORT
allocate a non-zero section for itself.
If your subroutine requires arguments in addition to the large arrays,
append them to the argument list for the call to EXTEND. They will be
passed to the subroutine. This is what a call to EXTEND looks like:
CALL EXTEND(SUBRTN,N, SCALAR1,SIZE1,...,SCALARN,SIZEN, ARG1,...,ARGm)
is a call to the EXTEND routine with m+2N+2 arguments, where:
SUBRTN Is the name of a Fortran subroutine to call using the N
large arrays, N array sizes and m extra values (ARG1...ARGm)
as arguments. SUBRTN should be declared to be EXTERNAL.
N Is the number of large arrays to generate.
SCALAR1, . . . Are N scalar variables of the same type as the array elements
SCALARN, in large array arguments to SUBRTN. Note that a CHARACTER
variable must be of the desired length for the elements of the
SIZE1, . . . Are N scalars of type INTEGER which give the number of elements
SIZEN in the large arrays. These arguments are passed on to SUBRTN
for use in adjustable array dimension declarations.
ARG1, . . . Are "m" arguments of any type which are passed on to SUBRTN
ARGm following the N large array arguments.
The EXTEND subroutine performs a call to SUBRTN that looks like this:
CALL SUBRTN(ARRAY1,SIZE1,...,ARRAYN,SIZEN, ARG1,...,ARGm)
Consider the following program for example:
DOUBLE PRECISION B,EPS
CALL EXTEND(FOO,3, A,1000000,B,1000000,C,100000, XVEC,EPS,CARD)
It will allocate an array of 1000000 real numbers (call it ARRAYA), an
array of 1000000 double precision numbers (ARRAYB) and an array of
100000 132 character long strings (ARRAYC). It will appear as if a
Fortran subroutine named EXTEND was called which looks like this:
DOUBLE PRECISION ARRAYB(1000000),EPS
Note that if the program is not started in a non-zero section, FOROTS
may fail in an unpredictable manner. EXTEND will abort the program
rather than let execution continue. One way to make the program start
in a non-zero section is to:
@LOAD FOO.FOR,EXTEND.REL ; Get a core image with code in section 0
@SAVE FOO.EXE ; Create .EXE file with code in section 0
@GET FOO.EXE/USE-SECTION:1 ; Get a core image with code in section 1
@SAVE FOO.EXE ; Create .EXE file with code in section 1
If EXTEND is on a system area (say, SYS:), then the first command is:
See your system administrator to find out where EXTEND.REL is.
You must be running a KL microcode later than version 275 (which is
the current field image version for Tops-20 releases 5 and 5.1) in
order to use EXTEND.