qml.specs now uses Resources class (#4015)

* init commit of feature branch * initial commit to add base resource class * tests + docs * lint * lint + fix docs * more lint + docs * update implementation to prevent updating attributes * lint * Apply suggestions from code review Co-authored-by: soranjh <40344468+soranjh@users.noreply.github.com> * Address review comments, add test for __eq__ op * lint * Added tests * pylint * code review comment * fix if * fix typo * Update pennylane/resource/resource.py Co-authored-by: Tom Bromley <49409390+trbromley@users.noreply.github.com> * code review comments * swapped over to data class implementation * keep default dict in count resource method * fix type hint * changelog * lint * ci * make count_resources private * Update pennylane/resource/resource.py Co-authored-by: soranjh <40344468+soranjh@users.noreply.github.com> * fixed docstring * changelog * remove support for custom ops * Added spec support and fixed bug printing default dicts * fix tests * code factor * fix tests * fix docs * Update pennylane/tape/qscript.py Co-authored-by: soranjh <40344468+soranjh@users.noreply.github.com> * add back missing dict keys, revert tests * Update pennylane/tape/qscript.py Co-authored-by: Utkarsh <utkarshazad98@gmail.com> --------- Co-authored-by: soranjh <40344468+soranjh@users.noreply.github.com> Co-authored-by: Tom Bromley <49409390+trbromley@users.noreply.github.com> Co-authored-by: Utkarsh <utkarshazad98@gmail.com>
PennyLaneAI · Apr 21, 2023 · a87fca3 · a87fca3
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diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
@@ -31,11 +31,11 @@
   <class 'pennylane.operation.Tensor'>
   ```
 
-* New `Resources` data class to store resources like number of gates and circuit depth throughout a 
+* The `Resources` data class is added to store resources like number of gates and circuit depth throughout a  
   quantum circuit.
   [(#3981)](https://github.com/PennyLaneAI/pennylane/pull/3981/)
 
-* A `_count_resources()` function was added to count the resources required when executing a 
+* The `_count_resources()` function is added to count the resources required when executing a 
   QuantumTape for a given number of shots.
   [(#3996)](https://github.com/PennyLaneAI/pennylane/pull/3996)
 
@@ -253,6 +253,10 @@
 * Update various Operators and templates to ensure their decompositions only return lists of Operators.
   [(#3243)](https://github.com/PennyLaneAI/pennylane/pull/3243)
 
+* `QuantumScript.specs` is modified to make use of the new `Resources` class. This also modifies the 
+  output of `qml.specs()`. 
+  [(#4015)](https://github.com/PennyLaneAI/pennylane/pull/4015)
+
 <h3>Breaking changes 💔</h3>
 
 * The `seed_recipes` argument has been removed from `qml.classical_shadow` and `qml.shadow_expval`.

diff --git a/pennylane/resource/resource.py b/pennylane/resource/resource.py
@@ -17,8 +17,6 @@
 from collections import defaultdict
 from dataclasses import dataclass, field
 
-from pennylane.tape import QuantumTape
-
 
 @dataclass(frozen=True)
 class Resources:
@@ -55,21 +53,25 @@ class Resources:
     shots: int = 0
 
     def __str__(self):
-        keys = ["wires", "gates", "depth", "shots", "gate_types"]
-        vals = [self.num_wires, self.num_gates, self.depth, self.shots, self.gate_types]
+        keys = ["wires", "gates", "depth", "shots"]
+        vals = [self.num_wires, self.num_gates, self.depth, self.shots]
         items = "\n".join([str(i) for i in zip(keys, vals)])
         items = items.replace("('", "")
         items = items.replace("',", ":")
         items = items.replace(")", "")
-        items = items.replace("{", "\n{")
+
+        gate_str = ", ".join(
+            [f"'{gate_name}': {count}" for gate_name, count in self.gate_types.items()]
+        )
+        items += "\ngate_types:\n{" + gate_str + "}"
         return items
 
     def _ipython_display_(self):
         """Displays __str__ in ipython instead of __repr__"""
         print(str(self))
 
 
-def _count_resources(tape: QuantumTape, shots: int) -> Resources:
+def _count_resources(tape, shots: int) -> Resources:
     """Given a quantum circuit (tape) and number of samples, this function
      counts the resources used by standard PennyLane operations.
 

diff --git a/pennylane/tape/qscript.py b/pennylane/tape/qscript.py
@@ -1143,38 +1143,46 @@ def specs(self):
             dict[str, Union[defaultdict,int]]: dictionaries that contain quantum script specifications
 
         **Example**
+         >>> ops = [qml.Hadamard(0), qml.RX(0.26, 1), qml.CNOT((1,0)),
+         ...         qml.Rot(1.8, -2.7, 0.2, 0), qml.Hadamard(1), qml.CNOT((0, 1))]
+         >>> qscript = QuantumScript(ops, [qml.expval(qml.PauliZ(0) @ qml.PauliZ(1))])
 
-        >>> ops = [qml.Hadamard(0), qml.RX(0.26, 1), qml.CNOT((1,0)),
-        ...         qml.Rot(1.8, -2.7, 0.2, 0), qml.Hadamard(1), qml.CNOT((0,1))]
-        >>> qscript = QuantumScript(ops, [qml.expval(qml.PauliZ(0) @ qml.PauliZ(1))])
-
-        Asking for the specs produces a dictionary as shown below:
+        Asking for the specs produces a dictionary of useful information about the circuit:
 
+        >>> qscript.specs['num_observables']
+        1
         >>> qscript.specs['gate_sizes']
-        defaultdict(int, {1: 4, 2: 2})
-        >>> qscript.specs['gate_types']
-        defaultdict(int, {'Hadamard': 2, 'RX': 1, 'CNOT': 2, 'Rot': 1})
-
-        As ``defaultdict`` objects, any key not present in the dictionary returns 0.
-
-        >>> qscript.specs['gate_types']['RZ']
-        0
-
+        defaultdict(<class 'int'>, {1: 4, 2: 2})
+        >>> print(qscript.specs['resources'])
+        wires: 2
+        gates: 6
+        depth: 4
+        shots: 0
+        gate_types:
+        {'Hadamard': 2, 'RX': 1, 'CNOT': 2, 'Rot': 1}
         """
         if self._specs is None:
-            self._specs = {"gate_sizes": defaultdict(int), "gate_types": defaultdict(int)}
+            resources = qml.resource.resource._count_resources(
+                self, shots=0
+            )  # pylint: disable=protected-access
+
+            self._specs = {
+                "resources": resources,
+                "gate_sizes": defaultdict(int),
+                "gate_types": defaultdict(int),
+            }
 
             for op in self.operations:
                 # don't use op.num_wires to allow for flexible gate classes like QubitUnitary
                 self._specs["gate_sizes"][len(op.wires)] += 1
                 self._specs["gate_types"][op.name] += 1
 
-            self._specs["num_operations"] = len(self.operations)
+            self._specs["num_operations"] = resources.num_gates
             self._specs["num_observables"] = len(self.observables)
             self._specs["num_diagonalizing_gates"] = len(self.diagonalizing_gates)
             self._specs["num_used_wires"] = self.num_wires
-            self._specs["depth"] = self.graph.get_depth()
             self._specs["num_trainable_params"] = self.num_params
+            self._specs["depth"] = resources.depth
 
         return self._specs
 

diff --git a/tests/legacy/test_qscript_old.py b/tests/legacy/test_qscript_old.py
@@ -430,14 +430,17 @@ def test_empty_qs_specs(self):
         assert qs.specs["gate_sizes"] == defaultdict(int)
         assert qs.specs["gate_types"] == defaultdict(int)
 
+        gate_types = defaultdict(int)
+        assert qs.specs["resources"] == qml.resource.Resources(gate_types=gate_types)
+
         assert qs.specs["num_operations"] == 0
         assert qs.specs["num_observables"] == 0
         assert qs.specs["num_diagonalizing_gates"] == 0
         assert qs.specs["num_used_wires"] == 0
         assert qs.specs["num_trainable_params"] == 0
         assert qs.specs["depth"] == 0
 
-        assert len(qs.specs) == 8
+        assert len(qs.specs) == 9
 
         assert qs._specs is qs.specs
 
@@ -449,10 +452,16 @@ def test_specs_tape(self, make_script):
         specs = qs.specs
         assert qs._specs is specs
 
-        assert len(specs) == 8
+        assert len(specs) == 9
 
         assert specs["gate_sizes"] == defaultdict(int, {1: 3, 2: 1})
         assert specs["gate_types"] == defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+
+        gate_types = defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+        assert specs["resources"] == qml.resource.Resources(
+            num_wires=3, num_gates=4, gate_types=gate_types, depth=3
+        )
+
         assert specs["num_operations"] == 4
         assert specs["num_observables"] == 2
         assert specs["num_diagonalizing_gates"] == 1

diff --git a/tests/resource/test_resource.py b/tests/resource/test_resource.py
@@ -15,6 +15,7 @@
 Test base Resource class and its associated methods
 """
 from dataclasses import FrozenInstanceError
+from collections import defaultdict
 import pytest
 
 import pennylane as qml
@@ -29,14 +30,14 @@ class TestResources:
     resource_quantities = (
         Resources(),
         Resources(5, 0, {}, 0, 0),
-        Resources(1, 3, {"Hadamard": 1, "PauliZ": 2}, 3, 10),
+        Resources(1, 3, defaultdict(int, {"Hadamard": 1, "PauliZ": 2}), 3, 10),
         Resources(4, 2, {"Hadamard": 1, "CNOT": 1}, 2, 100),
     )
 
     resource_parameters = (
         (0, 0, {}, 0, 0),
         (5, 0, {}, 0, 0),
-        (1, 3, {"Hadamard": 1, "PauliZ": 2}, 3, 10),
+        (1, 3, defaultdict(int, {"Hadamard": 1, "PauliZ": 2}), 3, 10),
         (4, 2, {"Hadamard": 1, "CNOT": 1}, 2, 100),
     )
 
@@ -61,22 +62,22 @@ def test_set_attributes_error(self):
                 setattr(r, attr_name, 1)
 
     test_str_data = (
-        ("wires: 0\n" + "gates: 0\n" + "depth: 0\n" + "shots: 0\n" + "gate_types: \n" + "{}"),
-        ("wires: 5\n" + "gates: 0\n" + "depth: 0\n" + "shots: 0\n" + "gate_types: \n" + "{}"),
+        ("wires: 0\n" + "gates: 0\n" + "depth: 0\n" + "shots: 0\n" + "gate_types:\n" + "{}"),
+        ("wires: 5\n" + "gates: 0\n" + "depth: 0\n" + "shots: 0\n" + "gate_types:\n" + "{}"),
         (
             "wires: 1\n"
             + "gates: 3\n"
             + "depth: 3\n"
             + "shots: 10\n"
-            + "gate_types: \n"
+            + "gate_types:\n"
             + "{'Hadamard': 1, 'PauliZ': 2}"
         ),
         (
             "wires: 4\n"
             + "gates: 2\n"
             + "depth: 2\n"
             + "shots: 100\n"
-            + "gate_types: \n"
+            + "gate_types:\n"
             + "{'Hadamard': 1, 'CNOT': 1}"
         ),
     )
@@ -89,7 +90,7 @@ def test_str(self, r, rep):
     test_rep_data = (
         "Resources(num_wires=0, num_gates=0, gate_types={}, depth=0, shots=0)",
         "Resources(num_wires=5, num_gates=0, gate_types={}, depth=0, shots=0)",
-        "Resources(num_wires=1, num_gates=3, gate_types={'Hadamard': 1, 'PauliZ': 2}, "
+        "Resources(num_wires=1, num_gates=3, gate_types=defaultdict(<class 'int'>, {'Hadamard': 1, 'PauliZ': 2}), "
         "depth=3, shots=10)",
         "Resources(num_wires=4, num_gates=2, gate_types={'Hadamard': 1, 'CNOT': 1}, "
         "depth=2, shots=100)",

diff --git a/tests/tape/test_qscript.py b/tests/tape/test_qscript.py
@@ -420,6 +420,7 @@ def test_empty_qs_specs(self):
         qs = QuantumScript()
         assert qs._specs is None
 
+        assert qs.specs["resources"] == qml.resource.Resources()
         assert qs.specs["gate_sizes"] == defaultdict(int)
         assert qs.specs["gate_types"] == defaultdict(int)
 
@@ -430,7 +431,7 @@ def test_empty_qs_specs(self):
         assert qs.specs["num_trainable_params"] == 0
         assert qs.specs["depth"] == 0
 
-        assert len(qs.specs) == 8
+        assert len(qs.specs) == 9
 
         assert qs._specs is qs.specs
 
@@ -442,7 +443,13 @@ def test_specs_tape(self, make_script):
         specs = qs.specs
         assert qs._specs is specs
 
-        assert len(specs) == 8
+        assert len(specs) == 9
+
+        gate_types = defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+        expected_resources = qml.resource.Resources(
+            num_wires=3, num_gates=4, gate_types=gate_types, depth=3
+        )
+        assert specs["resources"] == expected_resources
 
         assert specs["gate_sizes"] == defaultdict(int, {1: 3, 2: 1})
         assert specs["gate_types"] == defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})

diff --git a/tests/tape/test_tape.py b/tests/tape/test_tape.py
@@ -559,22 +559,32 @@ def test_specs_empty_tape(self, make_empty_tape):
         assert tape.specs["gate_sizes"] == defaultdict(int)
         assert tape.specs["gate_types"] == defaultdict(int)
 
+        gate_types = defaultdict(int)
+        expected_resources = qml.resource.Resources(num_wires=2, gate_types=gate_types)
+        assert tape.specs["resources"] == expected_resources
+
         assert tape.specs["num_operations"] == 0
         assert tape.specs["num_observables"] == 1
         assert tape.specs["num_diagonalizing_gates"] == 0
         assert tape.specs["num_used_wires"] == 2
         assert tape.specs["num_trainable_params"] == 0
         assert tape.specs["depth"] == 0
 
-        assert len(tape.specs) == 8
+        assert len(tape.specs) == 9
 
     def test_specs_tape(self, make_tape):
         """Tests that regular tapes return correct specifications"""
         tape = make_tape
 
         specs = tape.specs
 
-        assert len(specs) == 8
+        assert len(specs) == 9
+
+        gate_types = defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+        expected_resources = qml.resource.Resources(
+            num_wires=3, num_gates=4, gate_types=gate_types, depth=3
+        )
+        assert specs["resources"] == expected_resources
 
         assert specs["gate_sizes"] == defaultdict(int, {1: 3, 2: 1})
         assert specs["gate_types"] == defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
@@ -591,9 +601,16 @@ def test_specs_add_to_tape(self, make_extendible_tape):
         tape = make_extendible_tape
         specs1 = tape.specs
 
-        assert len(specs1) == 8
+        assert len(specs1) == 9
         assert specs1["gate_sizes"] == defaultdict(int, {1: 3, 2: 1})
         assert specs1["gate_types"] == defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+
+        gate_types = defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 1})
+        expected_resoures = qml.resource.Resources(
+            num_wires=3, num_gates=4, gate_types=gate_types, depth=3
+        )
+        assert specs1["resources"] == expected_resoures
+
         assert specs1["num_operations"] == 4
         assert specs1["num_observables"] == 0
         assert specs1["num_diagonalizing_gates"] == 0
@@ -609,64 +626,23 @@ def test_specs_add_to_tape(self, make_extendible_tape):
 
         specs2 = tape.specs
 
-        assert len(specs2) == 8
+        assert len(specs2) == 9
         assert specs2["gate_sizes"] == defaultdict(int, {1: 4, 2: 2})
         assert specs2["gate_types"] == defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 2, "RZ": 1})
+
+        gate_types = defaultdict(int, {"RX": 2, "Rot": 1, "CNOT": 2, "RZ": 1})
+        expected_resoures = qml.resource.Resources(
+            num_wires=5, num_gates=6, gate_types=gate_types, depth=4
+        )
+        assert specs2["resources"] == expected_resoures
+
         assert specs2["num_operations"] == 6
         assert specs2["num_observables"] == 2
         assert specs2["num_diagonalizing_gates"] == 1
         assert specs2["num_used_wires"] == 5
         assert specs2["num_trainable_params"] == 6
         assert specs2["depth"] == 4
 
-    def test_resources_empty_tape(self, make_empty_tape):
-        """Test that empty tapes return empty resource counts."""
-        tape = make_empty_tape
-
-        assert len(tape.specs["gate_types"]) == 0
-        assert tape.specs["depth"] == 0
-
-    def test_resources_tape(self, make_tape):
-        """Test that regular tapes return correct number of resources."""
-        tape = make_tape
-
-        depth = tape.specs["depth"]
-        assert depth == 3
-
-        # Verify resource counts
-        resources = tape.specs["gate_types"]
-        assert len(resources) == 3
-        assert resources["RX"] == 2
-        assert resources["Rot"] == 1
-        assert resources["CNOT"] == 1
-
-    def test_resources_add_to_tape(self, make_extendible_tape):
-        """Test that tapes return correct number of resources after adding to them."""
-        tape = make_extendible_tape
-
-        depth = tape.specs["depth"]
-        assert depth == 3
-
-        resources = tape.specs["gate_types"]
-        assert len(resources) == 3
-        assert resources["RX"] == 2
-        assert resources["Rot"] == 1
-        assert resources["CNOT"] == 1
-
-        with tape as tape:
-            qml.CNOT(wires=[0, 1])
-            qml.RZ(0.1, wires=3)
-            qml.expval(qml.PauliX(wires="a"))
-            qml.probs(wires=[0, "a"])
-
-        assert tape.specs["depth"] == 4
-        resources = tape.specs["gate_types"]
-        assert len(resources) == 4
-        assert resources["RX"] == 2
-        assert resources["Rot"] == 1
-        assert resources["CNOT"] == 2
-        assert resources["RZ"] == 1
-
 
 class TestParameters:
     """Tests for parameter processing, setting, and manipulation"""

diff --git a/tests/templates/test_state_preparations/test_mottonen_state_prep.py b/tests/templates/test_state_preparations/test_mottonen_state_prep.py
@@ -255,7 +255,7 @@ def circuit(state_vector):
         circuit(state_vector)
         tape = spy.call_args[0][0]
 
-        assert tape.specs["gate_types"]["CNOT"] == n_CNOT
+        assert tape.specs["resources"].gate_types["CNOT"] == n_CNOT
 
     def test_custom_wire_labels(self, tol):
         """Test that template can deal with non-numeric, nonconsecutive wire labels."""