Reorder Pauli terms before Trotterization #12925

altaris · 2024-08-08T08:28:29Z

Summary

Reordering the terms of a Pauli operator can reduce the depth of the evolution circuit if using the Lie-Trotter or Suzuki-Trotter methods. This PR adds the option to do just that.

Details and comments

This PR adds

the method synthesis.evolution.product_formula.reorder_paulis that reorders Pauli terms based on a greedy graph coloring heuristic;
the reorder option in the ProductFormula, LieTrotter and SuzukiTrotter constructors to allow for reordering before synthesis.

Reordering the terms of a Pauli operator can reduce the depth of the evolution circuit if using the Lie-Trotter or Suzuki-Trotter methods. This commit adds a method `synthesis.evolution.product_formula.reorder_paulis` that does just that, based on a greedy graph coloring heuristic. This commit also adds the `reorder` option in the `ProductFormula`, `LieTrotter` and `SuzukiTrotter` constructors to allow for reordering before synthesis.

qiskit-bot · 2024-08-08T08:28:35Z

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CLAassistant · 2024-08-08T08:28:37Z

All committers have signed the CLA.

qiskit/synthesis/evolution/product_formula.py

coveralls · 2024-08-08T10:37:01Z

Pull Request Test Coverage Report for Build 11729926405

Details

45 of 47 (95.74%) changed or added relevant lines in 6 files are covered.
9 unchanged lines in 3 files lost coverage.
Overall coverage increased (+0.004%) to 88.927%

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/synthesis/evolution/product_formula.py	25	26	96.15%
qiskit/synthesis/evolution/qdrift.py	3	4	75.0%

Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/unitary_synthesis.rs	1	92.2%
crates/qasm2/src/lex.rs	2	92.23%
crates/qasm2/src/parse.rs	6	97.62%

Totals
Change from base Build 11728606692:	0.004%
Covered Lines:	79062
Relevant Lines:	88907

💛 - Coveralls

qiskit/synthesis/evolution/lie_trotter.py

Cryoris · 2024-09-02T08:24:28Z

@altaris are you still pursuing this or do would you like us to help? 🙂

altaris · 2024-09-02T11:20:47Z

Sure! I'd love to see it through 💪

Before that, if reorder_paulis was given a single-term SparsePauliOp object, it would return it encapsulated in a list. Now, it returns it as is.

Cryoris

Overall the PR looks very nice! I left some comments below, in particular about the handling of lists of operators. Could you also add a release note describing the new argument? 🙂

qiskit/synthesis/evolution/product_formula.py

mrossinek

Just adding my 2 cents here

qiskit/synthesis/evolution/product_formula.py

If `reorder_paulis` is given a list of operators, then they are reordered and returned individually. Before this co mmit, they used to be added all together and then reordered, which always resulted in a single operator.

ShellyGarion

LGTM. thanks for the nice contribution to Qiskit. Some release notes are needed.

qiskit/synthesis/evolution/qdrift.py

alexanderivrii

Thanks @Cryoris and the original contributor @altaris! I think allowing Pauli reordering is a useful option for the PauliEvolutionGate synthesis algorithms.

I have left a few minor comments and questions inline.

One more question: do you think that for Rustiq-based synthesis algorithm (and the plugin already accepts "preserve_order"), it might be beneficial to rearrange Paulis before passing the pauli network to Rustiq?

qiskit/circuit/library/pauli_evolution.py

qiskit/synthesis/evolution/lie_trotter.py

qiskit/synthesis/evolution/product_formula.py

qiskit/synthesis/evolution/suzuki_trotter.py

Cryoris · 2024-11-07T12:55:21Z

One more question: do you think that for Rustiq-based synthesis algorithm (and the plugin already accepts "preserve_order"), it might be beneficial to rearrange Paulis before passing the pauli network to Rustiq?

That is already possible to do with this PR, since the re-ordering happens before expand. So we can expose this in the Rustiq plugin, just like in the default plugin. So we would re-order with the graph coloring and then allow Rustiq to also re-order? Or are they redundant together?

alexanderivrii · 2024-11-07T13:23:47Z

That is already possible to do with this PR, since the re-ordering happens before expand. So we can expose this in the Rustiq plugin, just like in the default plugin. So we would re-order with the graph coloring and then allow Rustiq to also re-order? Or are they redundant together?

I think it makes sense to expose this to Rustiq plugin as well. And I think it makes sense to let Rustiq do the additional reordering.

- add reno - docs - safer list concat

…er-paulis

Cryoris · 2024-11-07T17:10:22Z

56e619c includes this option in the Rustiq plugin too 👍🏻

mtreinish · 2024-11-07T18:33:58Z

qiskit/synthesis/evolution/lie_trotter.py

@@ -60,6 +60,7 @@ def __init__(
            | None
        ) = None,
        wrap: bool = False,
+        preserve_order: bool = False,


I thought the consensus here was to not reorder terms by default because of the potential performance overhead. Shouldn't the default be to True?

mtreinish · 2024-11-07T18:34:07Z

qiskit/synthesis/evolution/product_formula.py

@@ -63,6 +69,7 @@ def __init__(
            | None
        ) = None,
        wrap: bool = False,
+        preserve_order: bool = False,


Same question here

Suggested change

preserve_order: bool = False,

preserve_order: bool = True,

qiskit/synthesis/evolution/qdrift.py

alexanderivrii · 2024-11-07T18:42:07Z

qiskit/transpiler/passes/synthesis/hls_plugins.py

+        if "preserve_order" in options and isinstance(algo, ProductFormula):
+            algo.preserve_order = options["preserve_order"]
+


Thanks for adding this. A very small nitpick: we don't need another call to isinstance(also, ProductFormula) here, since we've just checked this on the line above.

mtreinish · 2024-11-07T18:45:27Z

I think given the open questions and the proximity to 1.3.0 (ie this is the last PR being tracked) it's probably better to defer this to 2.0.0 rather than force it in. This feature is a nice to have, but I don't think it's absolutely necessary for 1.3.0

raynelfss · 2024-11-07T19:03:05Z

Pushing to 2.0.0 after further discussion...

thanks Matthew!

alexanderivrii

Thanks @Cryoris. This PR very nicely concludes the work that was done to improve the support for Pauli evolutions: representing them as gates, improving expansion methods, adding the plugin interface, new synthesis algorithms and new options, porting relevant code to Rust.

mtreinish

I'm fine with merging this as is. I just have 2 small nits inline, but they can be fixed in a followup without issue and aren't worth blocking this over.

mtreinish · 2024-11-07T19:28:14Z

qiskit/synthesis/evolution/lie_trotter.py

+            preserve_order: If ``False``, allows reordering the terms of the operator to
+                potentially yield a shallower evolution circuit. Not relevant
+                when synthesizing operator with a single term.


I think from a docs perspective it would be good to explain the tradeoffs here, especially around runtime performance.

mtreinish · 2024-11-07T19:34:37Z

qiskit/synthesis/evolution/product_formula.py

+    terms = sorted(paulis, key=_term_sort_key)
+    graph = rx.PyGraph()
+    graph.add_nodes_from(terms)
+    indexed_nodes = list(enumerate(graph.nodes()))


I think you don't actually need to cast this is as a list, it should all work fine without it and save a copy.

altaris added 2 commits August 8, 2024 17:24

Added unit tests for Pauli reordering

5c61160

altaris requested review from alexanderivrii, ShellyGarion and a team as code owners August 8, 2024 08:28

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ShellyGarion requested a review from Cryoris August 8, 2024 10:10

altaris mentioned this pull request Aug 9, 2024

Reorder terms of a Pauli operator before Trotterization #12819

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Cryoris added this to the 1.3 beta milestone Aug 12, 2024

Cryoris reviewed Sep 2, 2024

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altaris added 4 commits September 3, 2024 20:32

reorder_paulis acts as the identity if the operator has only one term

758caff

Before that, if reorder_paulis was given a single-term SparsePauliOp object, it would return it encapsulated in a list. Now, it returns it as is.

Reorder Pauli terms by default

4c53dbc

reorder_paulis is deterministic and order-invariant

f0a6b3f

Fixed SuzukiTrotter unit tests

d98c019

mtreinish modified the milestones: 1.3 beta, 1.3.0 Sep 9, 2024

altaris added 2 commits September 12, 2024 11:52

No Pauli reordering by default

098dd29

Added Pauli reordering option in QDrift

6fc1b49

Cryoris reviewed Sep 12, 2024

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mrossinek reviewed Sep 12, 2024

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qiskit/synthesis/evolution/product_formula.py Outdated Show resolved Hide resolved

altaris added 3 commits September 12, 2024 18:47

Typset math correctly

1748ae9

Reorder ops individually

84f937e

If `reorder_paulis` is given a list of operators, then they are reordered and returned individually. Before this co mmit, they used to be added all together and then reordered, which always resulted in a single operator.

Option to change graph coloring heuristic

50e7d50

Cryoris added 3 commits November 6, 2024 17:09

consistent with rustiq

22fc36b

rm print, fix sorting

71cff0f

lint & docs

a588ec3

ShellyGarion reviewed Nov 7, 2024

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Cryoris reviewed Nov 7, 2024

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qiskit/synthesis/evolution/qdrift.py Outdated Show resolved Hide resolved

Fix QDrift reordering

d7c5f67

alexanderivrii reviewed Nov 7, 2024

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Cryoris added 3 commits November 7, 2024 15:08

review comments

56e619c

- add reno - docs - safer list concat

Merge branch 'reorder-paulis' of github.com:altaris/qiskit into reord…

7df41d1

…er-paulis

Merge branch 'main' into reorder-paulis

7089729

rm dead code

c192d87

mtreinish reviewed Nov 7, 2024

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alexanderivrii reviewed Nov 7, 2024

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raynelfss modified the milestones: 1.3.0, 2.0.0 Nov 7, 2024

Cryoris and others added 3 commits November 7, 2024 20:15

fix default value

80c4022

missed one

365f238

thanks Matthew!

Merge branch 'main' into reorder-paulis

5d57a61

alexanderivrii approved these changes Nov 7, 2024

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raynelfss modified the milestones: 2.0.0, 1.3.0 Nov 7, 2024

mtreinish reviewed Nov 7, 2024

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raynelfss enabled auto-merge November 7, 2024 19:38

mtreinish disabled auto-merge November 7, 2024 19:57

mtreinish merged commit 4251d01 into Qiskit:main Nov 7, 2024
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Reorder Pauli terms before Trotterization #12925

Reorder Pauli terms before Trotterization #12925

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		if "preserve_order" in options and isinstance(algo, ProductFormula):
		algo.preserve_order = options["preserve_order"]

Reorder Pauli terms before Trotterization #12925

Reorder Pauli terms before Trotterization #12925

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altaris commented Aug 8, 2024

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