Rewrite local expectation values as a single contraction #46
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Nice! I'll try and add some more tests to cover the onsite case later today, so let's wait just a second before merging |
lkdvos
previously approved these changes
Jun 19, 2024
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Looks like a good addition to me. I added the "optimal" contraction order, by taking an order which seems to be optimal at reasonable values of the physical, bond, and boundary dimensions, but there are a couple TensorOperations fixes that need to happen before I can properly make this automatically compute an optimal order.
In general, good to go for me, I know the onsite terms are not tested, but I would make this part of the operator rewrite anyways
lkdvos
approved these changes
Jun 19, 2024
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Rewrites the local expectation values as a single contraction and switches on the optimal contraction ordering in
@tensor. This should improve performance, since I'm a bit skeptical the approach of first contracting the full environment and then multiplying in the operator afterward is the most efficient. This currently bypasses theoperator_envfunction entirely, although I left it in just in case it is still needed elsewhere.In particular, this should fix the
OnSiteexpectation value, which was wrong before I think (it seems it assumed a transposed environment?). Also, I chose to transpose theNearestNeighborenvironment density matrix to be consistent with the usual interpretation.