Port synth_cnot_phase_aam to Rust

crates/accelerate/src/synthesis/linear/mod.rs

@@ -14,7 +14,7 @@ use crate::QiskitError;
 use numpy::{IntoPyArray, PyArray2, PyReadonlyArray2, PyReadwriteArray2};
 use pyo3::prelude::*;
 
-mod pmh;
+pub mod pmh;
 pub mod utils;
 
 #[pyfunction]

crates/accelerate/src/synthesis/linear/pmh.rs

@@ -13,7 +13,7 @@
 use hashbrown::HashMap;
 use ndarray::{s, Array1, Array2, ArrayViewMut2, Axis};
 use numpy::PyReadonlyArray2;
-use smallvec::smallvec;
+use smallvec::{smallvec, SmallVec};
 use std::cmp;
 
 use qiskit_circuit::circuit_data::CircuitData;
@@ -158,8 +158,20 @@ pub fn synth_cnot_count_full_pmh(
     matrix: PyReadonlyArray2<bool>,
     section_size: Option<i64>,
 ) -> PyResult<CircuitData> {
-    let arrayview = matrix.as_array();
-    let mut mat: Array2<bool> = arrayview.to_owned();
+    let mat: Array2<bool> = matrix.as_array().to_owned();
+    let num_qubits = mat.nrows();
+    let section_size: Option<usize> =
+        section_size.and_then(|num| if num >= 0 { Some(num as usize) } else { None });
+
+    let instructions = synth_pmh(mat, section_size);
+    CircuitData::from_standard_gates(py, num_qubits as u32, instructions, Param::Float(0.0))
+}
+
+type Instruction = (StandardGate, SmallVec<[Param; 3]>, SmallVec<[Qubit; 2]>);
+pub fn synth_pmh(
+    mut mat: Array2<bool>,
+    section_size: Option<usize>,
+) -> impl DoubleEndedIterator<Item = Instruction> {
     let num_qubits = mat.nrows(); // is a quadratic matrix
 
     // If given, use the user-specified input size. If None, we default to
@@ -169,7 +181,7 @@ pub fn synth_cnot_count_full_pmh(
     // until ~100 qubits.
     let alpha = 0.56;
     let blocksize = match section_size {
-        Some(section_size) => section_size as usize,
+        Some(section_size) => section_size,
         None => std::cmp::max(2, (alpha * (num_qubits as f64).log2()).floor() as usize),
     };
 
@@ -179,17 +191,15 @@ pub fn synth_cnot_count_full_pmh(
     let upper_cnots = lower_cnot_synth(mat.view_mut(), blocksize, true);
 
     // iterator over the gates
-    let instructions = upper_cnots
-        .iter()
-        .map(|(i, j)| (*j, *i))
+    upper_cnots
+        .into_iter()
+        .map(|(i, j)| (j, i))
         .chain(lower_cnots.into_iter().rev())
         .map(|(ctrl, target)| {
             (
                 StandardGate::CXGate,
                 smallvec![],
                 smallvec![Qubit(ctrl as u32), Qubit(target as u32)],
             )
-        });
-
-    CircuitData::from_standard_gates(py, num_qubits as u32, instructions, Param::Float(0.0))
+        })
 }