Symmetric matrices

[stevengj]

@juliohm

I would love to have these memory savings with big symmetric matrices, it sounds much smarter and efficient. I don’t have a clear picture of why this is not feasible

It’s only a factor of two in memory, which is usually not the difference between feasible and infeasible, and the price you pay is that operations on the packed format are much less efficient (you probably lose much more than a factor of two in performance for most matrix operations).