Documentation |
Display memory information
memory
userview = memory
[userview systemview] = memory
The memory function is available only on Microsoft^{®} Windows^{®} systems. Results are dependant on your computer hardware and the load on your computer.
memory displays information showing how much memory is available and how much the MATLAB^{®} software is currently using. The information displayed at your computer screen includes the following items, each of which is described in a section below:
userview = memory returns user-focused information on memory use in structure userview. The information returned in userview includes the following items, each of which is described in a section below:
[userview systemview] = memory returns both user- and system-focused information on memory use in structures userview and systemview, respectively. The userview structure is described in the command syntax above. The information returned in systemview includes the following items, each of which is described in a section below:
Each of the sections below describes a value that is displayed or returned by the memory function.
Maximum Possible Array is the size of the largest contiguous free memory block. As such, it is an upper bound on the largest single array MATLAB can create at this time.
MATLAB derives this number from the smaller of the following two values:
The largest contiguous memory block found in the MATLAB virtual address space
The total available system memory
To see how many array elements this number represents, divide by the number of bytes in the array class. For example, for a double array, divide by 8. The actual number of elements MATLAB can create is always fewer than this number.
When you enter the memory command without assigning its output, MATLAB displays this information as a string. When you do assign the output, MATLAB returns the information in a structure field. See the table below.
Command | Returned in |
---|---|
memory | String labelled Maximum possible array: |
user = memory | Structure field user.MaxPossibleArrayBytes |
All values are double-precision and in units of bytes.
When you enter the memory command without specifying any outputs, MATLAB may also display one of the following footnotes. 32-bit systems show either the first or second footnote; 64-bit systems show only the second footnote:
There is sufficient system memory to allow mapping of all virtual addresses in the largest available block of the MATLAB process. The maximum amount of total MATLAB virtual address space is either 2 GB or 3 GB, depending on whether the /3GB switch is in effect or not.
There is insufficient system memory to allow mapping of all virtual addresses in the largest available block of the MATLAB process.
Memory Available for All Arrays is the total amount of memory available to hold data. The amount of memory available is guaranteed to be at least as large as this field.
MATLAB derives this number from the smaller of the following two values:
The total available MATLAB virtual address space
The total available system memory
When you enter the memory command without assigning its output, MATLAB displays this information as a string. When you do assign the output, MATLAB returns the information in a structure field. See the table below.
Command | Returned in |
---|---|
memory | String labelled Memory available for all arrays: |
user = memory | Structure field user.MemAvailableAllArrays |
When you enter the memory command without specifying any outputs, MATLAB may also display one of the following footnotes. 32-bit systems show either the first or second footnote; 64-bit systems show only the latter footnote:
There is sufficient system memory to allow mapping of all available virtual addresses in the MATLAB process virtual address space to system memory. The maximum amount of total MATLAB virtual address space is either 2 GB or 3 GB, depending on whether the /3GB switch is in effect or not.
There is insufficient system memory to allow mapping of all available virtual addresses in the MATLAB process.
Memory Used By MATLAB is the total amount of system memory reserved for the MATLAB process. It is the sum of the physical memory and potential swap file usage.
When you enter the memory command without assigning its output, MATLAB displays this information as a string. When you do assign the output, MATLAB returns the information in a structure field. See the table below.
Command | Returned in |
---|---|
memory | String labelled Memory used by MATLAB: |
user = memory | Structure field user.MemUsedMATLAB |
Physical Memory (RAM) is the total physical memory (or RAM) in the computer.
When you enter the memory command without assigning its output, MATLAB displays this information as a string. See the table below.
Command | Returned in |
---|---|
memory | String labelled Physical Memory (RAM): |
Virtual Address Space is the amount of available and total virtual memory for the MATLAB process. MATLAB returns the information in two fields of the return structure: Available and Total.
Command | Return Value | Returned in Structure Field |
---|---|---|
[user,sys] = memory | Available memory | sys.VirtualAddressSpace.Available |
Total memory | sys.VirtualAddressSpace.Total |
You can monitor the difference:
VirtualAddressSpace.Total - VirtualAddressSpace.Available
as the Virtual Bytes counter in the Windows Performance program. (e.g., Windows XP Control Panel/Administrative Tool/Performance program).
System Memory is the amount of available system memory on your computer system. This number includes the amount of available physical memory and the amount of available swap file space on the computer running MATLAB. MATLAB returns the information in the SystemMemory field of the return structure.
Command | Return Value | Returned in Structure Field |
---|---|---|
[user,sys] = memory | Available memory | sys.SystemMemory |
This is the same as the difference:
limit - total (in bytes)
found in the Windows Task Manager: Performance/Commit Charge.
Physical Memory is the available and total amounts of physical memory (RAM) on the computer running MATLAB. MATLAB returns the information in two fields of the return structure: Available and Total.
Command | Value | Returned in Structure Field |
---|---|---|
[user,sys] = memory | Available memory | sys.PhysicalMemory.Available |
Total memory | sys.PhysicalMemory.Total |
Available physical memory is the same as:
Available (in bytes)
found in the Windows Task Manager: Performance/Physical Memory
The total physical memory is the same as
Total (in bytes)
found in the Windows Task Manager: Performance/Physical Memory
You can use the amount of available physical memory as a measure of how much data you can access quickly.
Display memory statistics on a 32-bit Windows system:
memory Maximum possible array: 677 MB (7.101e+008 bytes) * Memory available for all arrays: 1601 MB (1.679e+009 bytes) ** Memory used by MATLAB: 446 MB (4.681e+008 bytes) Physical Memory (RAM): 3327 MB (3.489e+009 bytes) * Limited by contiguous virtual address space available. ** Limited by virtual address space available.
Return in the structure userview, information on the largest array MATLAB can create at this time, how much memory is available to hold data, and the amount of memory currently being used by your MATLAB process:
userview = memory userview = MaxPossibleArrayBytes: 710127616 MemAvailableAllArrays: 1.6792e+009 MemUsedMATLAB: 468127744
Assign the output to two structures, user and sys, to obtain the information shown here:
[user sys] = memory; % --- Largest array MATLAB can create --- user.MaxPossibleArrayBytes ans = 710127616 % --- Memory available for data --- user.MemAvailableAllArrays ans = 1.6797e+009 % --- Memory used by MATLAB process --- user.MemUsedMATLAB ans = 467603456 % --- Virtual memory for MATLAB process --- sys.VirtualAddressSpace ans = Available: 1.6797e+009 Total: 2.1474e+009 % --- Physical memory and paging file --- sys.SystemMemory ans = Available: 4.4775e+009 % --- Computer's physical memory --- sys.PhysicalMemory ans = Available: 2.3941e+009 Total: 3.4889e+009