test_sparse.jl

function build_something_sparse_orig()
  vec_len = 70000

  row_ind = Uint64[]
  col_ind = Uint64[]
  value = Float64[]

  for j = 1:vec_len
     for k = 1:700
        ind = k*50
        push!(row_ind, ind)
        push!(col_ind, j)
        push!(value, 5.0)
     end
  end
  return (row_ind, col_ind, value)
end


function build_something_sparse()
  vec_len = 70000

  row_ind = zeros(Uint64, vec_len * 700)
  col_ind = zeros(Uint64, vec_len * 700)
  value = zeros(Float64, vec_len * 700)

  i = 1;
  @inbounds begin
    for j = 1:vec_len
       for k = 1:700
          row_ind[i] = k*50;
          col_ind[i] = j;
          value[i] = 5.0;
          i = i + 1;
       end
    end
  end
  return (row_ind, col_ind, value)
end

function build_something_sparse2()
  vec_len = 70000

  row_ind = zeros(Uint64, vec_len * 700)
  col_ind = zeros(Uint64, vec_len * 700)
  value = zeros(Float64, vec_len * 700)

  i = 1;
  @inbounds begin
    @simd for j = 1:vec_len
       @simd for k = 1:700
          row_ind[i] = k*50;
          col_ind[i] = j;
          value[i] = 5.0;
          i = i + 1;
       end
    end
  end
  return (row_ind, col_ind, value)
end

function build_something_sparse3()
  vec_len = 70000
  nnz = vec_len * 700

  row_ind = zeros(Uint64, nnz)
  col_ind = zeros(Uint64, vec_len+1)  # Assume ncol==vec_len
  value = 5*ones(Float64, nnz)

  i = 1;
  @inbounds begin
    @simd for j = 1:vec_len
       col_ind[j] = i;
       @simd for k = 1:700
          row_ind[i] = k*50;
          i = i + 1;
       end
    end
    col_ind[vec_len+1] = nnz + 1;
  end
  return (row_ind, col_ind, value)
end


(r,c,v) = build_something_sparse_orig();
@time (r,c,v) = build_something_sparse_orig();

(r,c,v) = build_something_sparse();
@time (r,c,v) = build_something_sparse();

(r,c,v) = build_something_sparse2();
@time (r,c,v) = build_something_sparse2();

A = sparse(r,c,v);
@time A = sparse(r,c,v);

(r,c,v) = build_something_sparse3();
@time (r,c,v) = build_something_sparse3();

nrow = ncol = length(c)-1;
A = SparseMatrixCSC(nrow, ncol, c,r,v);
@time A = SparseMatrixCSC(nrow, ncol, c,r,v);