[petsc-users] Memory for matrix assembly

[Jose E. Roman]

El 22/11/2011, a las 06:46, Andrej Mesaros escribió:

>>    Additionally, can I simply estimate the additional memory needed for
>>    SLEPc to find ~100 lowest eigenvalues?
>> Start with what is typically needed by PETSc (the matrix, the setup cost is for your preconditioner, the vectors for the Krylov method) and add 100*n*sizeof(PetscScalar).
> 
> To clarify, is "n" the matrix dimension? So that's memory for 100 vectors (the Krylov space) plus the memory already taken by PETSc when assembly is done?


By default, SLEPc uses a basis of 2*nev vectors, so 200 in your case. (See the value of ncv with -eps_view).
If you want to reduce this size, give a value to parameter mpd. For instance, mpd=30 and nev=100 will give ncv=130. See EPSSetDimensions().

Jose