[petsc-users] Reshaping a vector into a matrix

[Barry Smith]

On Jan 6, 2011, at 5:24 PM, S V N Vishwanathan wrote:

>>>> 2. Since each vec1,vec2,... is the same size, this is likely to
>>>> produce poor memory performance.  If you care about speed, I suggest
>>>> interlacing the values in vec1,...,veck.  In that case, you can create
>>>> an MAIJ matrix that acts on this "multi-vector".
> 
>>   You most definitely want to use the MAIJ.  MAIJ does not "repeat" X, it uses the 
>> original matrix passed in but does efficient multiple matrix-vector products at the same time.
> 
> Is there any place to read up about MAIJ matrices. I read the manual
> pages but they were rather cryptic. Perhaps some example code?

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/src/snes/examples/tutorials/ex48.c.html is the only example that uses. You can also look at its source code (linked directly from the manual page) to see what it does.


> 
> vishy
> 
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>