Merge remote-tracking branch 'qiskit/master' into move-loading-from-q…

…asm-to-quantum-circuit-static-methods

CHANGELOG.rst

@@ -45,6 +45,9 @@ Fixed
 - Fix hardcoded backend mapping tests (#521)
 - Removed ``_modifiers call`` from ``reapply`` (#534)
 - Fix circuit drawer issue with filename location on windows (#543)
+- Change initial qubit layout only if the backend coupling map is not satisfied (#527)
+- Fix incorrect unrolling of t to tdg in CircuitBackend (#557)
+- Fix issue with simulator extension commands not reapplying correctly (#556)
 
 
 `0.5.3`_ - 2018-05-29

qiskit/_compiler.py

@@ -12,6 +12,7 @@
 
 import copy
 import uuid
+import warnings
 
 import numpy as np
 import scipy.sparse as sp
@@ -27,14 +28,15 @@
 from .unroll import DagUnroller, DAGBackend, JsonBackend, Unroller, CircuitBackend
 from .mapper import (Coupling, optimize_1q_gates, coupling_list2dict, swap_mapper,
                      cx_cancellation, direction_mapper)
+from ._gate import Gate
 
 logger = logging.getLogger(__name__)
 
 
 def compile(circuits, backend,
             config=None, basis_gates=None, coupling_map=None, initial_layout=None,
             shots=1024, max_credits=10, seed=None, qobj_id=None, hpc=None,
-            skip_translation=False):
+            skip_transpiler=False, skip_translation=False):
     """Compile a list of circuits into a qobj.
 
     FIXME THIS FUNCTION WILL BE REWRITTEN IN VERSION 0.6. It will be a thin wrapper
@@ -52,8 +54,9 @@ def compile(circuits, backend,
         seed (int): random seed for simulators
         qobj_id (int): identifier for the generated qobj
         hpc (dict): HPC simulator parameters
-        skip_translation (bool): If True, bypass most of the compilation process and
+        skip_transpiler (bool): If True, bypass most of the compilation process and
             creates a qobj with minimal check nor translation
+        skip_translation (bool): DEPRECATED. Use skip_transpiler instead.
 
     Returns:
         obj: the qobj to be run on the backends
@@ -62,6 +65,12 @@ def compile(circuits, backend,
         QISKitError: if any of the circuit names cannot be found on the
             Quantum Program.
     """
+    if skip_translation:
+        warnings.warn(
+            "skip_translation will be called skip_transpiler in future versions.",
+            DeprecationWarning)
+        skip_transpiler = True
+
     if isinstance(circuits, QuantumCircuit):
         circuits = [circuits]
 
@@ -114,22 +123,18 @@ def compile(circuits, backend,
         else:
             job["config"]["seed"] = seed
 
-        if skip_translation:  # Just return the qobj, without any transformation or analysis
+        if skip_transpiler:  # Just return the qobj, without any transformation or analysis
             job["config"]["layout"] = None
             job["compiled_circuit_qasm"] = circuit.qasm()
             job["compiled_circuit"] = DagUnroller(
                 DAGCircuit.fromQuantumCircuit(circuit),
                 JsonBackend(job['config']['basis_gates'].split(','))).execute()
         else:
-            # Pick good initial layout if None is given and not simulator
             if initial_layout is None and not backend.configuration['simulator']:
-                best_sub = best_subset(backend, num_qubits)
-                initial_layout = {}
-                map_iter = 0
-                for key, value in circuit.get_qregs().items():
-                    for i in range(value.size):
-                        initial_layout[(key, i)] = ('q', best_sub[map_iter])
-                        map_iter += 1
+                # if coupling_map is not already satisfied, pick a good initial layout
+                # otherwise leave as q[i]->q[i]
+                if not _matches_coupling_map(circuit.data, backend.configuration['coupling_map']):
+                    initial_layout = _pick_best_layout(backend, num_qubits, circuit.get_qregs())
 
             dag_circuit, final_layout = compile_circuit(
                 circuit,
@@ -265,7 +270,7 @@ def load_unroll_qasm_file(filename, basis_gates='u1,u2,u3,cx,id'):
     return circuit_unrolled
 
 
-def best_subset(backend, n_qubits):
+def _best_subset(backend, n_qubits):
     """Computes the qubit mapping with the best
     connectivity.
 
@@ -317,6 +322,52 @@ def best_subset(backend, n_qubits):
     return best_map
 
 
+def _matches_coupling_map(instructions, coupling_map):
+    """ Iterate over circuit instructions set to check if multi-qubit instruction coupling
+        graphs match the qubit coupling graph in the backend.
+
+    Parameters:
+            instructions (List): List of circuit instructions. Not all instructions
+                                 are Gates, hence not multi-qubit.
+            coupling_map (List): Backend coupling map, represented as an
+                                          adjacency list.
+
+    Returns:
+            True: If there's at least one instruction that uses multiple qubits and
+                  these qubits coupling matches one of the backend couplings.
+
+            False: If there's no match between any of the instructions multiple qubits
+                   coupling, and one of the couplings from the backend.
+    """
+    for instruction in instructions:
+        if isinstance(instruction, Gate) and instruction.is_multi_qubit():
+            if instruction.get_qubit_coupling() not in coupling_map:
+                return False
+    return True
+
+
+def _pick_best_layout(backend, num_qubits, qregs):
+    """ Pick a convenient layout depending on the best matching qubit connectivity
+
+    Parameters:
+        backend (BaseBackend) : The backend with the coupling_map for searching
+        num_qubits (int): Number of qubits
+        qregs (List): The list of quantum registers
+
+    Returns:
+        initial_layout: A special ordered layout
+
+    """
+    best_sub = _best_subset(backend, num_qubits)
+    layout = {}
+    map_iter = 0
+    for key, value in qregs.items():
+        for i in range(value.size):
+            layout[(key, i)] = ('q', best_sub[map_iter])
+            map_iter += 1
+    return layout
+
+
 class QISKitCompilerError(QISKitError):
     """Exceptions raised during compilation"""
     pass

qiskit/_gate.py

@@ -24,10 +24,19 @@ def __init__(self, name, param, args, circuit=None):
         arg = list of pairs (Register, index)
         circuit = QuantumCircuit or CompositeGate containing this gate
         """
+        self._is_multi_qubit = False
+        self._qubit_coupling = []
+        number_of_arguments = 0
         for argument in args:
+            number_of_arguments += 1
+            if number_of_arguments > 1:
+                self._qubit_coupling.append(argument)
+                self._is_multi_qubit = True
+
             if not isinstance(argument[0], QuantumRegister):
                 raise QISKitError("argument not (QuantumRegister, int) "
                                   + "tuple")
+
         super().__init__(name, param, args, circuit)
 
     def inverse(self):
@@ -38,3 +47,13 @@ def q_if(self, *qregs):
         """Add controls to this gate."""
         # pylint: disable=unused-argument
         raise QISKitError("control not implemented")
+
+    def is_multi_qubit(self):
+        """Returns True if this Gate is uses multiple qubits as arguments"""
+        return self._is_multi_qubit
+
+    def get_qubit_coupling(self):
+        """Gets the coupling graph of the qubits in case this is a multi-qubit gate"""
+        if not self.is_multi_qubit():
+            raise QISKitError("Can't get the qubit coupling of non multi-qubit gates!")
+        return self._qubit_coupling

qiskit/_instruction.py

@@ -47,7 +47,7 @@ def check_circuit(self):
             raise QISKitError("Instruction's circuit not assigned")
 
     def c_if(self, classical, val):
-        """Add classical control on register clasical and value val."""
+        """Add classical control on register classical and value val."""
         self.check_circuit()
         self.circuit._check_creg(classical)
         if val < 0:

qiskit/_quantumprogram.py

@@ -932,14 +932,19 @@ def get_backend_parameters(self, backend):
     def compile(self, name_of_circuits=None, backend="local_qasm_simulator",
                 config=None, basis_gates=None, coupling_map=None,
                 initial_layout=None, shots=1024, max_credits=10, seed=None,
-                qobj_id=None, hpc=None, skip_translation=False):
+                qobj_id=None, hpc=None, skip_transpiler=False, skip_translation=False):
         """Compile the circuits into the execution list.
 
         .. deprecated:: 0.5
             The `coupling_map` parameter as a dictionary will be deprecated in
             upcoming versions. Using the coupling_map as a list is recommended.
         """
-
+        # pylint: disable=missing-param-doc, missing-type-doc
+        if skip_translation:
+            warnings.warn(
+                "skip_translation will be called skip_transpiler in future versions.",
+                DeprecationWarning)
+            skip_transpiler = True
         if isinstance(coupling_map, dict):
             coupling_map = coupling_dict2list(coupling_map)
             warnings.warn(
@@ -961,7 +966,7 @@ def compile(self, name_of_circuits=None, backend="local_qasm_simulator",
         qobj = qiskit.wrapper.compile(list_of_circuits, my_backend,
                                       config, basis_gates, coupling_map, initial_layout,
                                       shots, max_credits, seed, qobj_id, hpc,
-                                      skip_translation)
+                                      skip_transpiler)
         return qobj
 
     def reconfig(self, qobj, backend=None, config=None, shots=None, max_credits=None, seed=None):
@@ -1126,7 +1131,7 @@ def _run_internal(self, qobj_list):
     def execute(self, name_of_circuits=None, backend="local_qasm_simulator",
                 config=None, timeout=60, basis_gates=None,
                 coupling_map=None, initial_layout=None, shots=1024,
-                max_credits=3, seed=None, hpc=None, skip_translation=False):
+                max_credits=3, seed=None, hpc=None, skip_transpiler=False, skip_translation=False):
         """Execute, compile, and run an array of quantum circuits).
 
         This builds the internal "to execute" list which is list of quantum
@@ -1174,7 +1179,7 @@ def execute(self, name_of_circuits=None, backend="local_qasm_simulator",
                                 'omp_num_threads': Numeric
                             }
 
-            skip_translation (bool): If True, bypass most of the compilation process and
+            skip_transpiler (bool): If True, bypass most of the compilation process and
                 creates a qobj with minimal check nor translation
         Returns:
             Result: status done and populates the internal __quantum_program with the data.
@@ -1183,6 +1188,12 @@ def execute(self, name_of_circuits=None, backend="local_qasm_simulator",
             The `coupling_map` parameter as a dictionary will be deprecated in
             upcoming versions. Using the coupling_map as a list is recommended.
         """
+        # pylint: disable=missing-param-doc, missing-type-doc
+        if skip_translation:
+            warnings.warn(
+                "skip_translation will be called skip_transpiler in future versions.",
+                DeprecationWarning)
+            skip_transpiler = True
         # TODO: Jay: currently basis_gates, coupling_map, initial_layout, shots,
         # max_credits, and seed are extra inputs but I would like them to go
         # into the config
@@ -1191,7 +1202,7 @@ def execute(self, name_of_circuits=None, backend="local_qasm_simulator",
                             basis_gates=basis_gates,
                             coupling_map=coupling_map, initial_layout=initial_layout,
                             shots=shots, max_credits=max_credits, seed=seed,
-                            hpc=hpc, skip_translation=skip_translation)
+                            hpc=hpc, skip_transpiler=skip_transpiler)
         result = self.run(qobj, timeout=timeout)
         return result