[petsc-users] Efficient reuse of vectors and matrices

[Margreet Nool]

Dear list,

How can I reuse vectors and matrices efficiently?

Our program uses a lot of global matrices and vectors and I want to 
reduce the amount of memory. Are there PETSC functions, which check 
whether a Mat or Vec is already created or destroyed? Our programs have 
been written in Fortran90.

The program performs a time stepping process, and I want to know what 
the best way is  to create a global vector only once. As an example, a 
global vector Vec y is created as a result of a matrix-vector product A 
. x = y, by calling the PETSC function MatMult. After the first call the 
Vec Y has already been created.

1. Do we have to store the result into a temporary vector temp_vec and 
copy its values into Vec y and destroy temp_vec?
2. Do we have to destroy Vec y before a call of MatMult and store the 
result directly in Vec y?
3. Does there exist a better solution?

Thanks in advance,
Margreet Nool

-- 
Margreet Nool
CWI - Centrum Wiskunde & Informatica
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