[petsc-users] MATMPIBAIJ matrix allocation

[Heikki Virtanen]

Hi, I try to solve an eigenvalue problem (Ax = lambda B x) where A 
and B are complex matrices. Unfortunately, my data structures 
are not capable of handling directly complex numbers, yet. So,
I have to use 

                [re(A) -im(A)]
RealA  = [                    ]
                 [imA)   re(A)] 

matrices instead. How should I allocate matrices if I know
compressed sparse row matrix formats of A and B matrices. I have used
something like this.

ierr = MatCreate(PETSC_COMM_WORLD,&RealA); CHKERRQ(ierr);    
ierr = MatSetSizes(RealA,PETSC_DECIDE,PETSC_DECIDE,2*n,2*n); CHKERRQ(ierr);
ierr = MatSetType(RealA,MATMPIBAIJ); CHKERRQ(ierr);
ierr = MatSetBlockSize(RealA,2);CHKERRQ(ierr);
ierr = MatSetFromOptions(RealA);CHKERRQ(ierr);
                
ierr = MatMPIBAIJSetPreallocationCSR (RealA,2,rows,cols,0); CHKERRQ(ierr);
ierr = MatAssemblyBegin (RealA,MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);
ierr = MatAssemblyEnd (RealA,MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);

where n is the global size of matrix A. rows and cols are csr arrays of A.
Each submatrix of RealA matrix have the same nonzero pattern than A.
But I am not sure if this is correct, because when I print my matrices out
they look more like band matrices than block matrices.

-Heikki
 		 	   		  
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