
Ublas : 
From: Max Weinberg (max.weinberg_at_[hidden])
Date: 20050503 09:00:28
> Can you give an example, in which situation you check the equality of two
> matrices? I never needed it in my codes.
It happens quite often in my code, since I "misuse" the sparse matrices as
containers for nonnumeric objects.
> BTW: Using norm_1(AB) or norm_inf(AB) is a O(n*m) or O(nnz) operation.
Doing
> a elementwise comparison (optionally with short circuit) is O(n*m) or O(nnz),
> too. So there is no difference regarding the algorithmic complexity.
Well, this is worst case complexity which doesn't have so much meaning. Average
complexity would include as parameter the mean number D of elements that
differ. That would give something like O(nnz/(1+D)) [roughly] for the element
wise comparison, while the norm variant is stuck to O(nnz).
Max