Overloading fill psparsematrix

[amartinhuertas]

I think these changes will be needed by GridapDistributed.jl at some point

[fverdugo]

I always have the doubt if fill!(a,v) makes sense for sparse matrices for v!=0.

The SparseMatrixCSC has this behaviour. Note the difference between fill!(b,5) and fill!(c,0):

julia> using SparseArrays

julia> a = zeros(3,3);

julia> a[1,3]=3;

julia> a[3,2]=1;

julia> a[1,1]=3;

julia> a
3×3 Matrix{Float64}:
 3.0  0.0  3.0
 0.0  0.0  0.0
 0.0  1.0  0.0

julia> b = sparse(a)
3×3 SparseMatrixCSC{Float64, Int64} with 3 stored entries:
 3.0   ⋅   3.0
  ⋅    ⋅    ⋅ 
  ⋅   1.0   ⋅ 

julia> fill!(b,5)
3×3 SparseMatrixCSC{Float64, Int64} with 9 stored entries:
 5.0  5.0  5.0
 5.0  5.0  5.0
 5.0  5.0  5.0

julia> c = sparse(a)
3×3 SparseMatrixCSC{Float64, Int64} with 3 stored entries:
 3.0   ⋅   3.0
  ⋅    ⋅    ⋅ 
  ⋅   1.0   ⋅ 

julia> fill!(c,0)
3×3 SparseMatrixCSC{Float64, Int64} with 3 stored entries:
 0.0   ⋅   0.0
  ⋅    ⋅    ⋅ 
  ⋅   0.0   ⋅ 

[fverdugo]

We can merge this but we need to check that the fill value is == 0, otherwise we need to throw a "no implemented" error

[amartinhuertas]

I always have the doubt if fill!(a,v) makes sense for sparse matrices for v!=0.

There is a discussion in regards to this in JuliaLang/julia#17670

The SparseMatrixCSC has this behaviour. Note the difference between fill!(b,5) and fill!(c,0):

I did not know that. I think this is not mentioned in the link above, neither.

We can merge this but we need to check that the fill value is == 0, otherwise we need to throw a "no implemented" error

And what if you want to set all entries of the matrix to a given value different from zero? How do you do that?

[amartinhuertas]

And what if you want to set all entries of the matrix to a given value different from zero? How do you do that?

Ok, perhaps we should override the LinearAlgebra.fillstored! for PSparseMatrix better than Base.fill!. Agreed?

[fverdugo]

Ok, perhaps we should override the LinearAlgebra.fillstored! for PSparseMatrix better than Base.fill!. Agreed?

Yes! I was not aware of this function. Very usefull!

[amartinhuertas]

Yes! I was not aware of this function. Very usefull!

Ok. Done. The only inconvenience is that fillstored! is not exported from LinearAlgebra. Does it mean that it is more prone to change without notice?

[codecov-commenter]

Codecov Report

Merging #34 (3086f1d) into gridap_distributed (f4d2901) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@                  Coverage Diff                   @@
##           gridap_distributed      #34      +/-   ##
======================================================
+ Coverage               92.30%   92.34%   +0.04%     
======================================================
  Files                       8        8              
  Lines                    1962     1973      +11     
======================================================
+ Hits                     1811     1822      +11     
  Misses                    151      151              

Impacted Files	Coverage Δ
src/Interfaces.jl	91.52% <100.00%> (+0.07%)	⬆️

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