Thank you, Tim - I'll definitely check it out. Right now I can't seem to
find an efficient way of doing it, but there are a few tricks in
Iterators.jl that might work.
On Sunday, November 15, 2015 at 1:33:29 PM UTC-8, Tim Holy wrote:
>
> This may also be a case where writing an iterator that just visits the
> elements with i >= j might be what you want. You can study the
> implementation
> of CartesianIndex in Base for inspiration.
>
> --Tim
>
> On Saturday, November 14, 2015 02:18:45 PM hustf wrote:
> > I believe this work-in-progress type may be adapted? I wanted to make
> this
> > faster by using tuples or immutable fixed vectors to store the data or
> > whatnot, but I guess I'm currently stuck. Help wanted.
> >
> > Compared to looping unnecessarily over a full matrix, this speeds things
> up
> > by around 35%.
> >
> > immutable Maq7 <:AbstractMatrix{Int}
> > data::Array{Int64,2} # upper triangular except diagonal, stored as a
> > horizontal vector
> > width::Int64
> > function Maq7(mat::Matrix{Int64})
> > if issym(mat)
> > n=size(mat,1)
> > if n>1
> > v=mat[2:n,1]
> > for col = 2:(n-1)
> > append!(v,mat[(col+1):n,col])
> > end
> > new(v', size(mat,1))
> > else
> > error("Ouch, not > (1x1)")
> > end
> > else
> > error("Ouch, not square symmetric")
> > end
> > end
> > end
> > Base.size(A::Maq7)= A.width, A.width
> > Base.length(A::Maq7)= div(A.width*(A.width-1), 2)
> > Base.getindex(A::Maq7, i::Int) = Base.getindex(A.data, i)
> > function Base.getindex(A::Maq7, r::Int , c::Int )
> > if c > r
> > return getindex(A.data, div( (r-1)*(2*A.width -r) , 2 ) + c - r )
> > elseif r > c
> > return getindex(A.data, div( (c-1)*(2*A.width -c) , 2 ) + r - c )
> > else
> > return zero(eltype(A.data))
> > end
> > end
> > Base.linearindexing(::Type{Maq7}) = Base.LinearFast()
> >
> >
> >
> > Example:
> > julia> ms
> > 4x4 Array{Int64,2}:
> > 7 1 2 3
> > 1 8 4 5
> > 2 4 9 6
> > 3 5 6 10
> >
> >
> > julia> m=Maq7(ms)
> > 4x4 Maq7:
> > 0 1 2 3
> > 1 0 4 5
> > 2 4 0 6
> > 3 5 6 0
> >
> > julia> collect(m)
> > 6-element Array{Int64,1}:
> > 1
> > 2
> > 3
> > 4
> > 5
> > 6
> >
> >
> > julia> length(m)
> > 6
>
>
