Allow selection of drawing order in CircuitDrawer (solves #333)

projectq/backends/_circuits/_drawer.py

@@ -11,7 +11,6 @@
 #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
-
 """
 Contains a compiler engine which generates TikZ Latex code describing the
 circuit.
@@ -42,9 +41,9 @@ def __init__(self, gate, lines, ctrl_lines):
         self.id = -1
 
     def __eq__(self, other):
-        return (self.gate == other.gate and self.lines == other.lines and
-                self.ctrl_lines == other.ctrl_lines and
-                self.id == other.id)
+        return (self.gate == other.gate and self.lines == other.lines
+                and self.ctrl_lines == other.ctrl_lines
+                and self.id == other.id)
 
     def __ne__(self, other):
         return not self.__eq__(other)
@@ -153,6 +152,9 @@ def __init__(self, accept_input=False, default_measure=0):
         self._free_lines = []
         self._map = dict()
 
+        # Order in which qubit lines are drawn
+        self._drawing_order = []
+
     def is_available(self, cmd):
         """
         Specialized implementation of is_available: Returns True if the
@@ -190,7 +192,7 @@ def set_qubit_locations(self, id_to_loc):
             raise RuntimeError("set_qubit_locations() has to be called before"
                                " applying gates!")
 
-        for k in range(min(id_to_loc), max(id_to_loc)+1):
+        for k in range(min(id_to_loc), max(id_to_loc) + 1):
             if k not in id_to_loc:
                 raise RuntimeError("set_qubit_locations(): Invalid id_to_loc "
                                    "mapping provided. All ids in the provided"
@@ -221,7 +223,7 @@ def _print_cmd(self, cmd):
             self._free_lines.append(qubit_id)
 
         if self.is_last_engine and cmd.gate == Measure:
-            assert(get_control_count(cmd) == 0)
+            assert (get_control_count(cmd) == 0)
             for qureg in cmd.qubits:
                 for qubit in qureg:
                     if self._accept_input:
@@ -244,7 +246,9 @@ def _print_cmd(self, cmd):
         for l in all_lines:
             self._qubit_lines[l].append(item)
 
-    def get_latex(self):
+        self._drawing_order.append(all_lines[0])
+
+    def get_latex(self, ordered=False, draw_gates_in_parallel=True):
         """
         Return the latex document string representing the circuit.
 
@@ -256,6 +260,12 @@ def get_latex(self):
             python3 my_circuit.py | pdflatex
 
         where my_circuit.py calls this function and prints it to the terminal.
+
+        Args:
+            ordered(bool): flag if the gates should be drawn in the order they
+                were added to the circuit
+            draw_gates_in_parallel(bool): flag if parallel gates should be drawn
+                parallel (True), or not (False)
         """
         qubit_lines = dict()
 
@@ -271,10 +281,13 @@ def get_latex(self):
                     new_cmd.id = cmd.lines[0]
                 qubit_lines[new_line].append(new_cmd)
 
-        circuit = []
-        for lines in qubit_lines:
-            circuit.append(qubit_lines[lines])
-        return to_latex(qubit_lines)
+        drawing_order = None
+        if ordered:
+            drawing_order = self._drawing_order
+
+        return to_latex(qubit_lines,
+                        drawing_order=drawing_order,
+                        draw_gates_in_parallel=draw_gates_in_parallel)
 
     def receive(self, command_list):
         """

projectq/backends/_circuits/_drawer_test.py

@@ -11,7 +11,6 @@
 #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
-
 """
 Tests for projectq.backends.circuits._drawer.py.
 """
@@ -20,19 +19,17 @@
 
 from projectq import MainEngine
 from projectq.cengines import LastEngineException
-from projectq.ops import (H,
-                          X,
-                          CNOT,
-                          Measure)
+from projectq.ops import (H, X, CNOT, Measure)
 from projectq.meta import Control
 
 import projectq.backends._circuits._drawer as _drawer
 from projectq.backends._circuits._drawer import CircuitItem, CircuitDrawer
 
 
-def test_drawer_getlatex():
+@pytest.mark.parametrize("ordered", [False, True])
+def test_drawer_getlatex(ordered):
     old_latex = _drawer.to_latex
-    _drawer.to_latex = lambda x: x
+    _drawer.to_latex = lambda x, drawing_order, draw_gates_in_parallel: x
 
     drawer = CircuitDrawer()
     drawer.set_qubit_locations({0: 1, 1: 0})
@@ -46,13 +43,13 @@ def test_drawer_getlatex():
     X | qureg[0]
     CNOT | (qureg[0], qureg[1])
 
-    lines = drawer2.get_latex()
+    lines = drawer2.get_latex(ordered=ordered)
     assert len(lines) == 2
     assert len(lines[0]) == 4
     assert len(lines[1]) == 3
 
     # check if it was sent on correctly:
-    lines = drawer.get_latex()
+    lines = drawer.get_latex(ordered=ordered)
     assert len(lines) == 2
     assert len(lines[0]) == 3
     assert len(lines[1]) == 4