Implement MatrixGate and simplify __eq__ in BasicGate to improve performance (#288)

Author: cgogolin

docs/projectq.ops.rst

@@ -6,6 +6,7 @@ The operations collection consists of various default gates and is a work-in-pro
 .. autosummary::
 
 	projectq.ops.BasicGate
+	projectq.ops.MatrixGate
 	projectq.ops.SelfInverseGate
 	projectq.ops.BasicRotationGate
 	projectq.ops.BasicPhaseGate

projectq/backends/_sim/_simulator_test.py

@@ -30,8 +30,8 @@
 from projectq.cengines import (BasicEngine, BasicMapperEngine, DummyEngine,
                                LocalOptimizer, NotYetMeasuredError)
 from projectq.ops import (All, Allocate, BasicGate, BasicMathGate, CNOT,
-                          Command, H, Measure, QubitOperator, Rx, Ry, Rz, S,
-                          TimeEvolution, Toffoli, X, Y, Z)
+                          Command, H, MatrixGate, Measure, QubitOperator,
+                          Rx, Ry, Rz, S, TimeEvolution, Toffoli, X, Y, Z)
 from projectq.meta import Control, Dagger, LogicalQubitIDTag
 from projectq.types import WeakQubitRef
 
@@ -97,37 +97,32 @@ def receive(self, command_list):
         return None
 
 
-class Mock1QubitGate(BasicGate):
-        def __init__(self):
-            BasicGate.__init__(self)
-            self.cnt = 0
+class Mock1QubitGate(MatrixGate):
+    def __init__(self):
+        MatrixGate.__init__(self)
+        self.cnt = 0
 
-        @property
-        def matrix(self):
-            self.cnt += 1
-            return [[0, 1], [1, 0]]
+    @property
+    def matrix(self):
+        self.cnt += 1
+        return [[0, 1], [1, 0]]
 
 
-class Mock6QubitGate(BasicGate):
-        def __init__(self):
-            BasicGate.__init__(self)
-            self.cnt = 0
+class Mock6QubitGate(MatrixGate):
+    def __init__(self):
+        MatrixGate.__init__(self)
+        self.cnt = 0
 
-        @property
-        def matrix(self):
-            self.cnt += 1
-            return numpy.eye(2 ** 6)
+    @property
+    def matrix(self):
+        self.cnt += 1
+        return numpy.eye(2 ** 6)
 
 
 class MockNoMatrixGate(BasicGate):
-        def __init__(self):
-            BasicGate.__init__(self)
-            self.cnt = 0
-
-        @property
-        def matrix(self):
-            self.cnt += 1
-            raise AttributeError
+    def __init__(self):
+        BasicGate.__init__(self)
+        self.cnt = 0
 
 
 def test_simulator_is_available(sim):
@@ -147,15 +142,15 @@ def test_simulator_is_available(sim):
 
     new_cmd.gate = Mock1QubitGate()
     assert sim.is_available(new_cmd)
-    assert new_cmd.gate.cnt == 4
+    assert new_cmd.gate.cnt == 1
 
     new_cmd.gate = Mock6QubitGate()
     assert not sim.is_available(new_cmd)
-    assert new_cmd.gate.cnt == 4
+    assert new_cmd.gate.cnt == 1
 
     new_cmd.gate = MockNoMatrixGate()
     assert not sim.is_available(new_cmd)
-    assert new_cmd.gate.cnt == 7
+    assert new_cmd.gate.cnt == 0
 
 
 def test_simulator_cheat(sim):

projectq/ops/__init__.py

@@ -15,6 +15,7 @@
 from ._basics import (NotMergeable,
                       NotInvertible,
                       BasicGate,
+                      MatrixGate,
                       SelfInverseGate,
                       BasicRotationGate,
                       ClassicalInstructionGate,

projectq/ops/_basics.py

@@ -64,7 +64,7 @@ class NotInvertible(Exception):
 
 class BasicGate(object):
     """
-    Base class of all gates.
+    Base class of all gates. (Don't use it directly but derive from it)
     """
     def __init__(self):
         """
@@ -204,39 +204,19 @@ def __or__(self, qubits):
         apply_command(cmd)
 
     def __eq__(self, other):
-        """ Return True if equal (i.e., instance of same class).
-
-            Unless both have a matrix attribute in which case we also check
-            that the matrices are identical as people might want to do the
-            following:
-
-            Example:
-                .. code-block:: python
-
-                gate = BasicGate()
-                gate.matrix = numpy.matrix([[1,0],[0, -1]])
-        """
-        if hasattr(self, 'matrix'):
-            if not hasattr(other, 'matrix'):
-                return False
-        if hasattr(other, 'matrix'):
-            if not hasattr(self, 'matrix'):
-                return False
-        if hasattr(self, 'matrix') and hasattr(other, 'matrix'):
-            if (not isinstance(self.matrix, np.matrix) or
-                    not isinstance(other.matrix, np.matrix)):
-                raise TypeError("One of the gates doesn't have the correct "
-                                "type (numpy.matrix) for the matrix "
-                                "attribute.")
-            if (self.matrix.shape == other.matrix.shape and
-                np.allclose(self.matrix, other.matrix,
-                            rtol=RTOL, atol=ATOL,
-                            equal_nan=False)):
-                return True
-            else:
-                return False
+        """
+        Equality comparision
+
+        Return True if instance of the same class, unless other is an instance
+        of :class:MatrixGate, in which case equality is to be checked by testing
+        for existence and (approximate) equality of matrix representations.
+        """
+        if isinstance(other, self.__class__):
+            return True
+        elif isinstance(other, MatrixGate):
+            return NotImplemented
         else:
-            return isinstance(other, self.__class__)
+            return False
 
     def __ne__(self, other):
         return not self.__eq__(other)
@@ -248,6 +228,71 @@ def __hash__(self):
         return hash(str(self))
 
 
+class MatrixGate(BasicGate):
+    """
+    Defines a gate class whose instances are defined by a matrix.
+
+    Note:
+        Use this gate class only for gates acting on a small numbers of qubits.
+        In general, consider instead using one of the provided ProjectQ gates
+        or define a new class as this allows the compiler to work symbolically.
+
+    Example:
+
+        .. code-block:: python
+
+            gate = MatrixGate([[0, 1], [1, 0]])
+            gate | qubit
+    """
+    def __init__(self, matrix=None):
+        """
+        Initialize MatrixGate
+
+        Args:
+            matrix(numpy.matrix): matrix which defines the gate. Default: None
+        """
+        BasicGate.__init__(self)
+        self._matrix = np.matrix(matrix) if matrix is not None else None
+
+    @property
+    def matrix(self):
+        return self._matrix
+
+    @matrix.setter
+    def matrix(self, matrix):
+        self._matrix = np.matrix(matrix)
+
+    def __eq__(self, other):
+        """
+        Equality comparision
+
+        Return True only if both gates have a matrix respresentation and the
+        matrices are (approximately) equal. Otherwise return False.
+        """
+        if not hasattr(other, 'matrix'):
+            return False
+        if (not isinstance(self.matrix, np.matrix) or
+                not isinstance(other.matrix, np.matrix)):
+            raise TypeError("One of the gates doesn't have the correct "
+                            "type (numpy.matrix) for the matrix "
+                            "attribute.")
+        if (self.matrix.shape == other.matrix.shape and
+            np.allclose(self.matrix, other.matrix,
+                        rtol=RTOL, atol=ATOL,
+                        equal_nan=False)):
+            return True
+        return False
+
+    def __str__(self):
+        return("MatrixGate(" + str(self.matrix.tolist()) + ")")
+
+    def __hash__(self):
+        return hash(str(self))
+
+    def get_inverse(self):
+        return MatrixGate(np.linalg.inv(self.matrix))
+
+
 class SelfInverseGate(BasicGate):
     """
     Self-inverse basic gate class.

projectq/ops/_basics_test.py

@@ -21,7 +21,7 @@
 import pytest
 
 from projectq.types import Qubit, Qureg
-from projectq.ops import Command
+from projectq.ops import Command, X
 from projectq import MainEngine
 from projectq.cengines import DummyEngine
 
@@ -118,13 +118,12 @@ def test_basic_gate_compare():
     gate2 = _basics.BasicGate()
     assert gate1 == gate2
     assert not (gate1 != gate2)
-    gate3 = _basics.BasicGate()
+    gate3 = _basics.MatrixGate()
     gate3.matrix = np.matrix([[1, 0], [0, -1]])
     assert gate1 != gate3
-    gate4 = _basics.BasicGate()
+    gate4 = _basics.MatrixGate()
     gate4.matrix = [[1, 0], [0, -1]]
-    with pytest.raises(TypeError):
-        gate4 == gate3
+    assert gate4 == gate3
 
 
 def test_comparing_different_gates():
@@ -295,3 +294,35 @@ def __init__(self):
     # Test a=2, b=3, and c=5 should give a=2, b=3, c=11
     math_fun = gate.get_math_function(("qreg1", "qreg2", "qreg3"))
     assert math_fun([2, 3, 5]) == [2, 3, 11]
+
+
+def test_matrix_gate():
+    gate1 = _basics.MatrixGate()
+    gate2 = _basics.MatrixGate()
+    with pytest.raises(TypeError):
+        assert gate1 == gate2
+    gate3 = _basics.MatrixGate([[0, 1], [1, 0]])
+    gate4 = _basics.MatrixGate([[0, 1], [1, 0]])
+    gate5 = _basics.MatrixGate([[1, 0], [0, -1]])
+    assert gate3 == gate4
+    assert gate4 != gate5
+    with pytest.raises(TypeError):
+        assert gate1 != gate3
+    with pytest.raises(TypeError):
+        assert gate3 != gate1
+    gate6 = _basics.BasicGate()
+    assert gate6 != gate1
+    assert gate6 != gate3
+    assert gate1 != gate6
+    assert gate3 != gate6
+    gate7 = gate5.get_inverse()
+    gate8 = _basics.MatrixGate([[1, 0], [0, (1+1j)/math.sqrt(2)]])
+    assert gate7 == gate5
+    assert gate7 != gate8
+    gate9 = _basics.MatrixGate([[1, 0], [0, (1-1j)/math.sqrt(2)]])
+    gate10 = gate9.get_inverse()
+    assert gate10 == gate8
+    assert gate3 == X
+    assert X == gate3
+    assert str(gate3) == "MatrixGate([[0, 1], [1, 0]])"
+    assert hash(gate3) == hash("MatrixGate([[0, 1], [1, 0]])")

projectq/ops/_gates.py

@@ -37,6 +37,7 @@
 
 from projectq.ops import get_inverse
 from ._basics import (BasicGate,
+                      MatrixGate,
                       SelfInverseGate,
                       BasicRotationGate,
                       BasicPhaseGate,

projectq/setups/decompositions/arb1qubit2rzandry_test.py

@@ -23,8 +23,8 @@
 from projectq.backends import Simulator
 from projectq.cengines import (AutoReplacer, DecompositionRuleSet,
                                DummyEngine, InstructionFilter, MainEngine)
-from projectq.ops import (BasicGate, ClassicalInstructionGate, Measure, Ph, R,
-                          Rx, Ry, Rz, X)
+from projectq.ops import (BasicGate, ClassicalInstructionGate, MatrixGate,
+                          Measure, Ph, R, Rx, Ry, Rz, X)
 from projectq.meta import Control
 
 from . import arb1qubit2rzandry as arb1q
@@ -51,7 +51,7 @@ def test_recognize_incorrect_gates():
     # Does not have matrix attribute:
     BasicGate() | qubit
     # Two qubit gate:
-    two_qubit_gate = BasicGate()
+    two_qubit_gate = MatrixGate()
     two_qubit_gate.matrix = [[1, 0, 0, 0], [0, 1, 0, 0],
                              [0, 0, 1, 0], [0, 0, 0, 1]]
     two_qubit_gate | qubit
@@ -121,7 +121,7 @@ def create_test_matrices():
 def test_decomposition(gate_matrix):
     for basis_state in ([1, 0], [0, 1]):
         # Create single qubit gate with gate_matrix
-        test_gate = BasicGate()
+        test_gate = MatrixGate()
         test_gate.matrix = np.matrix(gate_matrix)
 
         correct_dummy_eng = DummyEngine(save_commands=True)
@@ -165,7 +165,7 @@ def test_decomposition(gate_matrix):
                                          [[0, 2], [4, 0]],
                                          [[1, 2], [4, 0]]])
 def test_decomposition_errors(gate_matrix):
-    test_gate = BasicGate()
+    test_gate = MatrixGate()
     test_gate.matrix = np.matrix(gate_matrix)
     rule_set = DecompositionRuleSet(modules=[arb1q])
     eng = MainEngine(backend=DummyEngine(),

projectq/setups/decompositions/carb1qubit2cnotrzandry_test.py

@@ -21,8 +21,8 @@
 from projectq.cengines import (AutoReplacer, DecompositionRuleSet,
                                DummyEngine, InstructionFilter, MainEngine)
 from projectq.meta import Control
-from projectq.ops import (All, BasicGate, ClassicalInstructionGate, Measure,
-                          Ph, R, Rx, Ry, Rz, X, XGate)
+from projectq.ops import (All, BasicGate, ClassicalInstructionGate,
+                          MatrixGate, Measure, Ph, R, Rx, Ry, Rz, X, XGate)
 from projectq.setups.decompositions import arb1qubit2rzandry_test as arb1q_t
 
 from . import carb1qubit2cnotrzandry as carb1q
@@ -57,7 +57,7 @@ def test_recognize_incorrect_gates():
         # Does not have matrix attribute:
         BasicGate() | qubit
         # Two qubit gate:
-        two_qubit_gate = BasicGate()
+        two_qubit_gate = MatrixGate()
         two_qubit_gate.matrix = np.matrix([[1, 0, 0, 0], [0, 1, 0, 0],
                                            [0, 0, 1, 0], [0, 0, 0, 1]])
         two_qubit_gate | qubit
@@ -94,7 +94,7 @@ def test_recognize_v(gate_matrix):
 @pytest.mark.parametrize("gate_matrix", arb1q_t.create_test_matrices())
 def test_decomposition(gate_matrix):
     # Create single qubit gate with gate_matrix
-    test_gate = BasicGate()
+    test_gate = MatrixGate()
     test_gate.matrix = np.matrix(gate_matrix)
 
     for basis_state in ([1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0],