Re: [deal.II] PETSc Sparse LU Preallocation

Hi Lucas and Wolfgang I have something to say on this issue because I think it might be helpful to Lucas or other users. I know large memory usage is unavoidable in direct solvers. But I guess Lucas' issue with MUMPS was that he did not know how to reuse the factorization like one always does

Re: [deal.II] PETSc Sparse LU Preallocation

> Yes, you need good preconditioners! I am investigating this now. I have to admit I was overwhelmed with the plethora of options, but I am going through Barrett et al's Template Book now, and I hope it will help. On 7 December 2017 at 18:26, Wolfgang Bangerth wrote:

Re: [deal.II] PETSc Sparse LU Preallocation

Thanks for your thoughts on this. I have tried to use iterative solvers, but they all seem to fail after at some point, Yes, you need good preconditioners! and it seems that the maximum number of iterations in every one of them is capped at 1. No, you can select that in the

Re: [deal.II] PETSc Sparse LU Preallocation

Dear Wolfgang, > I think there's little to gain from trying to tweak the memory allocation part of this. The fact that MUMPS takes a lot of memory is also nothing you can change -- that's just what you get for using a direct solver. Thanks for your thoughts on this. I have tried to use

Re: [deal.II] PETSc Sparse LU Preallocation

Lucas, I mean that the LU Decomposition solver takes a huge amount of RAM, and it seems to me that allocating that once and reusing the space would be better. Attached you can find a simple graph* showing how the free memory in time. I ran an instance of my program using around 164k cells,

Re: [deal.II] PETSc Sparse LU Preallocation

Dear Wolfgang, I just noticed a minor mistake on the graph: two of the arrows are slightly misplaced. While this does not change the main message, I am still sending you the corrected figure. Lucas On 7 December 2017 at 16:28, Lucas Campos wrote: > Dear Wolfgang, > > I am

Re: [deal.II] PETSc Sparse LU Preallocation

On 12/07/2017 03:12 AM, Lucas Campos wrote: Currently I am using a direct LU solver via PETSc/MUMPS to solve my matrix. However, I have noticed that I spend a lot of time in allocation, at every step. Is it possible (or useful) to preallocate the internal structures necessary to solve the

[deal.II] PETSc Sparse LU Preallocation

Dear all, Currently I am using a direct LU solver via PETSc/MUMPS to solve my matrix. However, I have noticed that I spend a lot of time in allocation, at every step. Is it possible (or useful) to preallocate the internal structures necessary to solve the matrix? According to [1], it is