[petsc-dev] strangness in Chebyshev estimate of eigenvalues

[Mark Adams]

OK, I thought you were suggesting that:

unsigned int hash(unsigned int x) {
    x = ((x >> 16) ^ x) * 0x45d9f3b;
    x = ((x >> 16) ^ x) * 0x45d9f3b;
    x = ((x >> 16) ^ x);
    return x;}

But, Barry is vetoing this.

On Tue, May 17, 2016 at 4:18 PM, Jed Brown <jed at jedbrown.org> wrote:

> Mark Adams <mfadams at lbl.gov> writes:
>
> > Why not just set each index with hash(i) = (i >> 32)^i and forget
> > VecSetRandom in here?
>
> Because if your vertices are numbered lexicographically on a Cartesian
> grid, this gives you a plane.  But just put in the legit hash (the one I
> linked is pretty good) and then you don't have to worry about
> accidentally stumbling upon pathological cases.
>
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