MEMORY

The MEMORY function returns information on the amount of dynamic memory currently in use by the IDL session if no keywords are set. If a keyword is set, MEMORY returns the specified quantity.

Note: This function reports the amount of memory used by IDL’s core process. It does not include memory that is allocated by external libraries.

Examples

To determine how much dynamic memory is required to execute a sequence of IDL code:

; Get current allocation and reset the high water mark:

start_mem = MEMORY(/CURRENT)

; Arbitrary code goes here.

PRINT, 'Memory required: ', MEMORY(/HIGHWATER) - start_mem

The MEMORY function can also be used in conjunction with DIALOG_MESSAGE as follows:

; Get current dymanic memory in use:
mem = MEMORY(/CURRENT)
; Prepare dialog message:
message = 'Current amount of dynamic memory used is '
sentence = message + STRTRIM(mem,2)+' bytes.'
; Display the dialog message containing memory usage statement:
status = DIALOG_MESSAGE (sentence, /INFORMATION)

Syntax

Result = MEMORY( [, /CURRENT | , /HIGHWATER | , /NUM_ALLOC | , /NUM_FREE | , /STRUCTURE ] [, /L64] )

Return Value

The return value is a vector that is always of integer type. The following table describes the information returned if no keywords are set.

Element	Contents
Result[0]	Amount of dynamic memory (in bytes) currently in use by the IDL session.
Result[1]	The number of times IDL has made a memory allocation request from the underlying system.
Result[2]	The number of times IDL has made a request to free memory from the underlying system.
Result[3]	High water mark: The maximum amount of dynamic memory used since the last time the MEMORY function or HELP, /MEMORY procedure was called.

Arguments

None.

Keywords

Note: The following keywords determine the return value of the MEMORY function. Except for L64, all of the keywords are mutually exclusive; specify at most one of the following.

CURRENT

Set this keyword to return the amount of dynamic memory (in bytes) currently in use by the IDL session.

HIGHWATER

Set this keyword to return the maximum amount of dynamic memory used since the last time the MEMORY function or HELP,/MEMORY procedure was called. This can be used to determine maximum memory use of a code sequence as shown in the example below.

L64

By default, the result of MEMORY is 32-bit integer when possible, and 64-bit integer if the size of the returned values requires it. Set L64 to force 64-bit integers to be returned in all cases.

Note: Only 64-bit versions of IDL are capable of using enough memory to require 64-bit MEMORY output. Check the value of !VERSION.MEMORY_BITS to see if your IDL is 64-bit or not.

NUM_ALLOC

Returns the number of times IDL has requested dynamic memory from the underlying system.

NUM_FREE

Returns the number of times IDL has returned dynamic memory to the underlying system.

STRUCTURE

Set this keyword to return all available information about Expression in a structure. The result will be an IDL_MEMORY (32-bit) structure when possible, and an IDL_MEMORY64 structure otherwise. Set L64 to force an IDL_MEMORY64 structure to be returned in all cases.

The following are descriptions of the fields in the returned structure:

Field	Description
CURRENT	Current dynamic memory in use.
NUM_ALLOC	Number of calls to allocate memory.
NUM_FREE	Number of calls to free memory.
HIGHWATER	Maximum dynamic memory used since last call for this information.

Version History

Original

Introduced