Flipping Bits in a Sparse Matrix- Expanding stored entries

General Usage
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1

My sparse bit array is not dropping non zeros when flipping bits between rows (assignment optimization problem)

8766×11125 SparseArrays.SparseMatrixCSC{Bool,Int64} with 8766 stored entries:
  [7244,    1]  =  1
  [2111,  291]  =  1
  [2357,  347]  =  1
  [8071,  432]  =  1
  ⋮
  [2517, 9187]  =  1
  [1756, 9189]  =  1
  [1857, 9194]  =  1
  [2977, 9195]  =  1

My flip Bit code is as follows (I’m also open to better ways at doing this!)

x1=10
x2=20

y1=starts[x1,:].nzind[1]
y2=starts[x2,:].nzind[1]

starts[x1,y1] = false
starts[x2, y2] = false

starts[x1,y2] = true
starts[x2, y1] = true

My problem is that starts initially was stoing 8766 Values, and now stores 8768 values

julia> starts
8766×11125 SparseArrays.SparseMatrixCSC{Bool,Int64} with 8768 stored entries:
  [7244,    1]  =  1
  [2111,  291]  =  1
  [2357,  347]  =  1
  [8071,  432]  =  1
  ⋮
  [2517, 9187]  =  1
  [1756, 9189]  =  1
  [1857, 9194]  =  1
  [2977, 9195]  =  1

notably, its carrying both values

2×11125 SparseArrays.SparseMatrixCSC{Bool,Int64} with 4 stored entries:
  [1, 7773]  =  1
  [2, 7773]  =  0
  [1, 9028]  =  0
  [2, 9028]  =  1

How can I continue to only store nonzero (true) values?

2

dropzeros! gets rid of 0 entries. It requires iterating over all the entires though, so if you’re manually flipping bits, there might be a more efficient way to just delete that entry in the array.

3

For this your of operation, csc is a really bad format. I would try using a dok instead as they have much faster insertion and deletion times