From 6aa933cc0627d0d64cfcda53055db4f460f21b28 Mon Sep 17 00:00:00 2001
From: Matthew Treinish <mtreinish@kortar.org>
Date: Fri, 9 Aug 2024 18:21:29 -0400
Subject: [PATCH] Use ahash for IndexMap and IndexSet hasher (#12935)

The ahash hasher offers better performace as a drop in replacement for
the stdlib hash algorithm. This is a large reason we use the hashbrown
crate for our HashMap type in Qiskit (along with rayon support). The
indexmap crate doesn't use ahash by default however, so we typically
switch to it anywhere we use IndexMap or IndexSet to match the lookup
performance of hashbrown in places where we need to preserve insertion
order. However, there were a couple of spots where we missed this in the
rust code, this commit corrects these oversights.
---
 Cargo.lock                                                   | 1 +
 Cargo.toml                                                   | 1 +
 crates/accelerate/Cargo.toml                                 | 2 +-
 crates/accelerate/src/synthesis/clifford/greedy_synthesis.rs | 5 +++--
 crates/qasm3/Cargo.toml                                      | 1 +
 crates/qasm3/src/build.rs                                    | 5 ++++-
 6 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 4858af1971e9..5b2ee803ee4a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1222,6 +1222,7 @@ dependencies = [
 name = "qiskit-qasm3"
 version = "1.3.0"
 dependencies = [
+ "ahash 0.8.11",
  "hashbrown 0.14.5",
  "indexmap",
  "oq3_semantics",
diff --git a/Cargo.toml b/Cargo.toml
index a505a4e7c22b..5fffe8ff4dd7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ ndarray = "^0.15.6"
 numpy = "0.21.0"
 smallvec = "1.13"
 thiserror = "1.0"
+ahash = "0.8.11"
 
 # Most of the crates don't need the feature `extension-module`, since only `qiskit-pyext` builds an
 # actual C extension (the feature disables linking in `libpython`, which is forbidden in Python
diff --git a/crates/accelerate/Cargo.toml b/crates/accelerate/Cargo.toml
index 0b23cf08743e..854c1ed05706 100644
--- a/crates/accelerate/Cargo.toml
+++ b/crates/accelerate/Cargo.toml
@@ -15,7 +15,7 @@ numpy.workspace = true
 rand = "0.8"
 rand_pcg = "0.3"
 rand_distr = "0.4.3"
-ahash = "0.8.11"
+ahash.workspace = true
 num-traits = "0.2"
 num-complex.workspace = true
 num-bigint.workspace = true
diff --git a/crates/accelerate/src/synthesis/clifford/greedy_synthesis.rs b/crates/accelerate/src/synthesis/clifford/greedy_synthesis.rs
index e53e25282005..81ddfb1d6503 100644
--- a/crates/accelerate/src/synthesis/clifford/greedy_synthesis.rs
+++ b/crates/accelerate/src/synthesis/clifford/greedy_synthesis.rs
@@ -10,6 +10,7 @@
 // copyright notice, and modified files need to carry a notice indicating
 // that they have been altered from the originals.
 
+use ahash::RandomState;
 use indexmap::IndexSet;
 use ndarray::{s, ArrayView2};
 use smallvec::smallvec;
@@ -102,7 +103,7 @@ pub struct GreedyCliffordSynthesis<'a> {
     symplectic_matrix: SymplecticMatrix,
 
     /// Unprocessed qubits.
-    unprocessed_qubits: IndexSet<usize>,
+    unprocessed_qubits: IndexSet<usize, RandomState>,
 }
 
 impl GreedyCliffordSynthesis<'_> {
@@ -121,7 +122,7 @@ impl GreedyCliffordSynthesis<'_> {
             smat: tableau.slice(s![.., 0..2 * num_qubits]).to_owned(),
         };
 
-        let unprocessed_qubits: IndexSet<usize> = (0..num_qubits).collect();
+        let unprocessed_qubits = (0..num_qubits).collect();
 
         Ok(GreedyCliffordSynthesis {
             tableau,
diff --git a/crates/qasm3/Cargo.toml b/crates/qasm3/Cargo.toml
index 4dd0d977786e..8e42f3f0701b 100644
--- a/crates/qasm3/Cargo.toml
+++ b/crates/qasm3/Cargo.toml
@@ -14,3 +14,4 @@ pyo3.workspace = true
 indexmap.workspace = true
 hashbrown.workspace = true
 oq3_semantics = "0.6.0"
+ahash.workspace = true
diff --git a/crates/qasm3/src/build.rs b/crates/qasm3/src/build.rs
index f5cf2fd4efca..912066df839e 100644
--- a/crates/qasm3/src/build.rs
+++ b/crates/qasm3/src/build.rs
@@ -13,6 +13,8 @@
 use pyo3::prelude::*;
 use pyo3::types::{PySequence, PyString, PyTuple};
 
+use ahash::RandomState;
+
 use hashbrown::HashMap;
 use indexmap::IndexMap;
 
@@ -190,8 +192,9 @@ impl BuilderState {
         let qubits = if let Some(asg_qubits) = barrier.qubits().as_ref() {
             // We want any deterministic order for easier circuit reproducibility in Python space,
             // and to include each seen qubit once.  This simply maintains insertion order.
-            let mut qubits = IndexMap::<*const ::pyo3::ffi::PyObject, Py<PyAny>>::with_capacity(
+            let mut qubits = IndexMap::<*const ::pyo3::ffi::PyObject, Py<PyAny>, RandomState>::with_capacity_and_hasher(
                 asg_qubits.len(),
+                RandomState::default()
             );
             for qarg in asg_qubits.iter() {
                 let qarg = expr::expect_gate_operand(qarg)?;