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MATLAB Central > MATLAB Newsreader > create large sparse FEM matrix > out of memory 

Subject: create large sparse FEM matrix > out of memory From: A B Date: 10 Aug, 2009 14:39:03 Message: 1 of 8 
Hi, 
Subject: create large sparse FEM matrix > out of memory From: Bruno Luong Date: 10 Aug, 2009 15:40:36 Message: 2 of 8 
"A B" <gitsnedbutzi@hotmail.com> wrote in message <h5pbe7$nc2$1@fred.mathworks.com>... 
Subject: create large sparse FEM matrix > out of memory From: A B Date: 10 Aug, 2009 17:43:02 Message: 3 of 8 
> There is something odd about the description. With a system of 25000 elements and 80e6 nonnull entries, that means each of the element has in average 80e6/25e3 = 3200. That doesn't sound right. The average ratio should be about 10 depends on the element type you use, but in no way it could reaches 3200. 
Subject: create large sparse FEM matrix > out of memory From: Bruno Luong Date: 10 Aug, 2009 18:00:22 Message: 4 of 8 
"A B" <gitsnedbutzi@hotmail.com> wrote in message <h5pm76$ou1$1@fred.mathworks.com>... 
Subject: create large sparse FEM matrix > out of memory From: A B Date: 10 Aug, 2009 18:25:20 Message: 5 of 8 
> I see, but many of them must have the same indices. You don't need to list them all and build the stiffness matrix. I bet the final matrix has much less than 80 millions nonzero elements. 
Subject: create large sparse FEM matrix > out of memory From: A B Date: 10 Aug, 2009 18:32:03 Message: 6 of 8 
btw. i'm also thinking of switching to a c++ spare matrix library (preferably mtl4). have you got any idea on how fast matlab sparse is on operations as additions and multiplication compared to one of the common c++ libraries? 
Subject: create large sparse FEM matrix > out of memory From: Thomas Clark Date: 10 Aug, 2009 22:45:20 Message: 7 of 8 
A B 
Subject: create large sparse FEM matrix > out of memory From: A B Date: 11 Aug, 2009 06:50:21 Message: 8 of 8 
Hi, 
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