The size of the memory pool is determined by the FMS parameter MAXMD. FMS keeps track of the memory used out of the pool with the Parameter MDUSED. At any point you may determine how much memory is left in the pool as follows:
CALL FMSIGT('MAXMD', MAXMD)
CALL FMSIGT('MDUSED', MDUSED)
MDLEFT = MAXMD - MDUSED
You may allocate memory form this pool for scratch data storage. This has the following advantages for your application:
The first step in using memory in the FMS memory pool is to declare an array in your program that you will use to reference the allocated memory. There are currently two mechanisms used to do this. Refer to the README.TXT file distributed with your copy of FMS for the details of your machine.
POINTER (CMD_PTR, CMD) POINTER (RMD_PTR, RMD) POINTER (IMD_PTR, IMD) COMPLEX*16 CMD(0:1) REAL*8 RMD(0:1) INTEGER IMD(0:1) ... CALL FMSIGT ('MEMPTR',CMD_PTR) CALL FMSIGT ('MEMPTR',RMD_PTR) CALL FMSIGT ('MEMPTR',IMD_PTR)
COMMON CMD EQUIVALENCE (IMD, RMD, CMD) COMPLEX*16 CMD(0:1) REAL*8 RMD(0:1) INTEGER IMD(0:1)
On most machines, FMS automatically aligns BLANK COMMON on a 16-byte boundary.
You should not be concerned if you use BLANK COMMON for other purposes. FMS does not store any data in CMD(0:1). It simply uses the arrays IMD, RMD and CMD as reference points for the allocated memory.
Once the reference arrays are established in your subroutine, you call FMSIMG to allocate LEN integer words starting at IMD(LOC), FMSRMG to allocate LEN REAL*8 words starting at RMD(LOC), or FMSCMG to allocate LEN COMPLEX*16 words starting at CMD(LOC).
The value of LOC returned is relative to the array value you provide on the call. For example, if you make the call:
CALL FMSIMG (IMD(10), LOC, LEN)the allocated memory will start at IMD(10+LOC).
You may make the value of LOC be an actual subscript of the array by dimensioning the array to start at 0,
INTEGER IMD (0:1)Then when you call the memory allocation subroutine
CALL FMSIMG (IMD, LOC, LEN)the allocated memory will start at IMD(LOC).
When you no longer require the storage, you can return it to the pool by calling
If you want to list the contents of the FMS memory pool, you can include the statement
You should return the memory you allocated to the memory pool before calling the FMS matrix algebra subroutines. This will prevent memory from being idle during FMS processing.
If you use the FMS parallel processing utilities to run part of your application in parallel, you may also call the FMS memory management routines from within your application. Each process will allocate a private region from the memory pool. For example, if you have 8 processes running and each calls the FMS memory management routines to allocate a region of memory, a total of 8 regions will be allocated.