I see. returning a new, smaller instance of the matrix was my temporary solution. Bummer that it's necessary... Is it really so strange to want to change the size of a
Another alternative which occurs to me is to make some child class of SparseCSCMatrix with two more arrays, each with one element, which track the sizes? Since I am making the matrix smaller, not larger, I can't imagine that this would be an issue. However, if I need to allocate two large sparse matrices just to remove a row/col pair, then I can suddenly use half the memory I could before... On Saturday, November 5, 2016 at 7:42:55 PM UTC-4, Jared Crean wrote: > > When a type is immutable, that means you can't modify the data in the > type. If a field of a type is mutable, a reference to it is stored in the > type, and you cannot modify that reference. In the case of > SparseMatrixCSC, that means you can't make A.colptr point to a different > array, for example. You are still free to change the values in A.colptr, > because that does not require modifying the reference. If the field is > immutable, then the value itself is stored in the type, not a reference to > the value, and you cannot modify the value. That's why you get the error > in the example. > > The best solution I can think of for your rmCol example is to create a new > SparseMatrixCSC that uses the same arrays as the old one (to avoid > increasing memory usage) and return it. Replacing the last line of rmCol > with: > > SparseMatrixCSC(m, n-1, A.colptr, A.rowval, A.nzval) > > should do the trick. The only sticky point is that the original A now > contains invalid data, so you'll have to make sure only the the matrix > returned from rmCol is used in the future, not the original A. > > Jared Crean > > > On Saturday, November 5, 2016 at 5:07:45 PM UTC-4, Corbin Foucart wrote: >> >> The SparseMatrixCSC type is immutable, which I understand to mean that I >> must respect the types of the attributes of SparseMatrixCSC types, as well >> as not changing the attributes themselves. >> >> The following gives a loadError (type is immutable). I am confused that >> I can modify the colptr and rowval attributes of A, but not the A.n >> attribute. Why is this? I am trying to change the size of a sparse matrix >> after removing the data from a row and column. >> >> I have checked that both A.n and A.n - 1 are type Int. >> >> function rmCol(A::SparseMatrixCSC, rmCol::Int) >> colRmRange = A.colptr[rmCol]:(A.colptr[rmCol+1]-1) >> filter!(e -> e != rmCol, A.colptr) >> >> deleteat!(A.rowval, rowval[colRmRange]) >> deleteat!(A.nzval, colRmRange) >> A.n -= 1 # inclusion of this line throws error >> >> end >> >
