Re: memory issues
- To: mathgroup at smc.vnet.net
- Subject: [mg68811] Re: memory issues
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Sat, 19 Aug 2006 00:41:24 -0400 (EDT)
- Organization: The Open University, Milton Keynes, UK
- References: <ec3pme$2a0$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Christoph Lhotka wrote: > Hi! > > Running Mathematica 5.2 on 64Bit (AMD) with 2GB of RAM Memory OS: WindowsXP 64 > Pro. I get the message: No more memory available. Mathematica Kernel has shut > down... > > How do I find out: > [ ... ] > 5) Why does my dual core processor does not work higher than with 50% The thread "Illusory Multicore Support in 5.2?", April 2006, should answer your question, http://forums.wolfram.com/mathgroup/archive/2006/Apr/msg00673.html > > Doing some tests on my own I got the following riddle: > > In[]:=ByteCount[1] > Out[]:=16 > > In[]:=2000000000/16 > Out[]:=125000000 > > In[]:=DAT=Table[i,{i,1,125000000}]; > > In[]:=ByteCount[DAT] > Out[]:=500000056 > > In[]:=MaxMemoryUsed[] > Out[]:= 502133312 > > Why is a list of 125 000 000 different integers (a 16 Byte) only 500 000 000 > Bytes long? How should I estimate the memory limits in my algorithms, when > designing them on this basis? Mathematica uses packed arrays: "When appropriate, large lists and nested lists of numbers are automatically stored as packed arrays of machine-sized integers or real numbers [1], [2]." Regards, Jean-Marc [1] "A.9.2 Data Structures and Memory Management" http://documents.wolfram.com/mathematica/book/section-A.9.2 [2] "Packed Array Summary" http://documents.wolfram.com/mathematica/Built-inFunctions/AdvancedDocumentation/LinearAlgebra/LinearAlgebraInMathematica/Performance/PackedArrays/AdvancedDocumentationLinearAlgebra5.0.2.html