The function vopen() initializes the vmm
system. The file $$$$vmem.tmp is created on a disk.
This is the temporary memory file where the matrices are
stored in row major order. You can specify the disk for
opening the file on through the environment variable
TMP. Use the DOS command SET TMP=D:
before running your YAMP program. This will tell the
program to use the D drive for the virtual file. The
current disk is used if you do not use the environment
variable. If you use a RAM disk, then the paging scheme is
reasonably fast. There is a performance penalty for using a
physical disk. Note that the vmm file can grow as large as
32 megabytes, so your decision to use a RAM disk hinges on
the space requirements of your application. There can be
at most 65536 blocks, each at 512 bytes, so there can be at
most 33,554,432 bytes (or 32,768 Kbytes) in
$$$$vmem.tmp.
vopen() is called when the first virtual matrix is constructed, so it does not need to be called for the matrix application.
vclose() closes the virtual memory file and shuts down the virtual memory pointers. This function should be called before exiting the program. If vclose() is not called, $$$$vmem.tmp is not deleted from the disk.