Weird missing memory usage for a global variable
in [Matlab]
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From: CSB on 13 Apr 2010 15:50 I was trying to assess the memory requirements of some code and came across something that makes no sense to me. Unfortunately I can't provide the code needed to reproduce this but I'm hopeful that my description will be enough for someone to know what's going on here. Here's what I'm seeing from a fresh re-start of MATLAB: ---------------------------- BEGIN -------------------------------------- >> global globalVar >> memory Maximum possible array: 1494 MB (1.567e+009 bytes) * Memory available for all arrays: 2594 MB (2.720e+009 bytes) ** Memory used by MATLAB: 230 MB (2.413e+008 bytes) Physical Memory (RAM): 3582 MB (3.756e+009 bytes) * Limited by contiguous virtual address space available. ** Limited by virtual address space available. >> codeToCreateAndFillGlobalVar() >> whos('globalVar') Name Size Bytes Class Attributes globalVar 1x1 2147483647 struct global >> memory Maximum possible array: 1207 MB (1.266e+009 bytes) * Memory available for all arrays: 2544 MB (2.667e+009 bytes) ** Memory used by MATLAB: 282 MB (2.953e+008 bytes) Physical Memory (RAM): 3582 MB (3.756e+009 bytes) * Limited by contiguous virtual address space available. ** Limited by virtual address space available. ---------------------------- END -------------------------------------- So, how is this possible?! I create a global variable that consumes over 2GB but the memory used by MATLAB increases by only 52 MB. More than that, it appears to be accurate in that I am still able to create matrices that fill the 2+ GB reported as available. What am I missing?
From: Loren Shure on 14 Apr 2010 14:41 In article <hq2hu0$lm3$1(a)fred.mathworks.com>, cbrundick(a)hotmail.com says... > I was trying to assess the memory requirements of some code and came across something that makes no sense to me. Unfortunately I can't provide the code needed to reproduce this but I'm hopeful that my description will be enough for someone to know what's going on here. Here's what I'm seeing from a fresh re-start of MATLAB: > > ---------------------------- BEGIN -------------------------------------- > > >> global globalVar > >> memory > Maximum possible array: 1494 MB (1.567e+009 bytes) * > Memory available for all arrays: 2594 MB (2.720e+009 bytes) ** > Memory used by MATLAB: 230 MB (2.413e+008 bytes) > Physical Memory (RAM): 3582 MB (3.756e+009 bytes) > > * Limited by contiguous virtual address space available. > ** Limited by virtual address space available. > > >> codeToCreateAndFillGlobalVar() > >> whos('globalVar') > Name Size Bytes Class Attributes > > globalVar 1x1 2147483647 struct global > >> memory > Maximum possible array: 1207 MB (1.266e+009 bytes) * > Memory available for all arrays: 2544 MB (2.667e+009 bytes) ** > Memory used by MATLAB: 282 MB (2.953e+008 bytes) > Physical Memory (RAM): 3582 MB (3.756e+009 bytes) > > * Limited by contiguous virtual address space available. > ** Limited by virtual address space available. > > ---------------------------- END -------------------------------------- > > So, how is this possible?! I create a global variable that consumes over 2GB but the memory used by MATLAB increases by only 52 MB. More than that, it appears to be accurate in that I am still able to create matrices that fill the 2+ GB reported as available. > > What am I missing? > maybe you created the struct where the fields share data between them implicitly, until the values differ? Depends on codeToCreateAndFillGlobalVar details... -- Loren http://blogs.mathworks.com/loren http://matlabwiki.mathworks.com/MATLAB_FAQ
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