On Wed, Oct 7, 2009 at 4:19 PM, Ondrej Certik <ond...@certik.cz> wrote:
>
> On Wed, Oct 7, 2009 at 3:46 PM, Brian Granger <ellisonbg....@gmail.com>
> wrote:
> > Øyvind,
> >
> > It will take me a while to go through everything, but I just read through
> > some of it quickly. It all looks quite
> > powerful and nice. One minor thing and one question:
> >
> > * In various places you use the variable "str." This is dangerous as str
> is
> > a builtin type (a string).
> >
> > * It is a little awkward to have the occupation #'s stored differently
> for
> > bosons and fermion. For bosons
> > it looks like you store the list of occupation #'s (dense format) but for
> > fermions, the indices of occupied states
> > (sparse format). Did you do this for performance/algorithmic reasons?
> For
> > states with a few particles but many states the sparse
> > structure of your fermionic approach would be better, but as the number
> of
> > particles approaches the number
> > of states, I think the sparse format doesn't give any advantage. I am
> > wondering if we can use the same
> > storage format for both bosons and fermions. Sparse for both? Dense for
> > both?
> >
> > * Am I correct that you are using assumptions to keep track of whether or
> > not an index is above or
> > below the fermi surface. Are you using the new assumptions system? I
> > haven't followed this very
> > closely - Ondrej can you comment on which should be used?
>
> Currently the old system, and once we finish the new system, the new
> system should be used.
>
> However, this:
>
> + @property
> + def is_above_fermi(self):
> + """
> + Does the index of this FermionicOperator allow values above fermi?
> + """
> + return not self.args[0].assumptions0.get("below_fermi")
>
>
> will cause problems, because the new assumption system doesn't store
> the assumptions within the symbols. One could use global assumptions,
> or remember them locally in the instance though and the new system
> should allow to create new assumptions easily.
>
> Why not to store this information in the FermionicOperator(SqOperator)
> instance itself? (And not use assumptions at all?)
>
>
But doesn't this seem like a good application of assumptions?
Brian
> >
> > I will look at this more and play with it all.
>
> I'll play with it in the evening.
>
> Ondrej
>
> >
>
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