If it's dense within the band, then what you really want is issue 8240. Are
you dealing with symmetric positive definite, symmetric indefinite, or
nonsymmetric? Eigenproblems or linear system solves? There are LAPACK
methods for banded matrices that should be more efficient than using
Cholmod or UMFPACK here, since they don't need to do anywhere near as much
integer arithmetic as SuiteSparse would (to represent a band matrix in CSC
format). We just don't have a Julia type for band matrices yet or ccall
wrappers around the corresponding LAPACK methods. I'm not sure whether
Jiahao made much progress on any prototypes, but banded matrices could
easily be worked on outside of base at first.
On Tuesday, August 11, 2015 at 4:42:18 PM UTC-7, Jared Crean wrote:
>
> Its a classical dense-within-the-band matrix (from a Finite Element
> problem).
>
> I want access to the solvers that are already supported by
> SparseMatrixCSC, and interfacing them to another new type seems like a lot
> of work. If there were an abstract CSC matrix type, this could be made
> much easier. I've been hoping issues #8001, #9906, and #9928 would lead in
> that direction, but so far they haven't.
>
> The syntax is really what I am after with the overriding of the methods.
> Using a macro is a safer alternative. I'll have to try that at some point.
>
> Jared Crean
>
> On Tuesday, August 11, 2015 at 7:25:06 PM UTC-4, Tony Kelman wrote:
>>
>> For storing explicit zeros you're best off modifying nzvals directly.
>>
>> In what way are you specializing your banded getindex method? Is this a
>> classical banded but dense-within-the-band matrix, or general CSC sparse
>> but with additional knowledge that no nonzeros ever have i and j different
>> by more than the bandwidth? You're probably better off either making a new
>> type for this that just wraps a SparseMatrixCSC for storage and either
>> stores or is parameterized by the bandwidth, or using a different method
>> other than getindex for this. If you'll miss the syntax, you could write a
>> macro to locally replace getindex with your specialized version.
>>
>>
>> On Tuesday, August 11, 2015 at 1:00:58 PM UTC-7, Jared Crean wrote:
>>>
>>> For a problem I am working on, I need to be able to store explicit zeros
>>> in a SparseMatrixCSC. While the storage format supports this, the
>>> setindex! method does not. Also, for banded sparse matricies I can define a
>>> much more efficient getindex method than the generic one. When I define my
>>> own method (importing the one from Base and then creating a method with the
>>> same signature as the existing one) I get warnings of the type:
>>>
>>>
>>> Warning: Method definition
>>> getindex(Base.SparseMatrix.SparseMatrixCSC{#T<:Any, Ti<:Integer}, Integer,
>>> Integer) in module SparseMatrix at sparse/sparsematrix.jl:1232 overwritten
>>> in module PDESolverCommon at
>>> /users/creanj/.julia/v0.4/PDESolverCommon/src/sparse.jl:63.
>>>
>>> My question is in what contexts is the method overwritten? In my local
>>> context (the REPL session where I use the one I created). Do functions
>>> within Base use the one in Base or the local one?
>>>
>>> Jared Crean
>>>
>>>
>>>
