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Refactor OpenQASM 2 exporter #9953

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Apr 17, 2023
Merged

Refactor OpenQASM 2 exporter #9953

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ab9114d
Refactor OpenQASM 2 exporter
jakelishman Apr 12, 2023
e619d50
Style tweak
jakelishman Apr 17, 2023
c4b872b
Merge remote-tracking branch 'ibm/main' into qasm2/rewrite-exporter
jakelishman Apr 17, 2023
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29 changes: 8 additions & 21 deletions qiskit/circuit/library/generalized_gates/permutation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -145,10 +145,6 @@ def __init__(
)
pattern = np.array(pattern)

# This is needed to support qasm()
self._qasm_name = "permutation__" + "_".join([str(n) for n in pattern]) + "_"
self._qasm_definition = None

super().__init__(name="permutation", num_qubits=num_qubits, params=[pattern])

def __array__(self, dtype=None):
Expand Down Expand Up @@ -183,21 +179,12 @@ def inverse(self):

return PermutationGate(pattern=_inverse_pattern(self.pattern))

def qasm(self):
"""The qasm for a permutation."""

if not self._qasm_definition:

# pylint: disable=cyclic-import
from qiskit.synthesis.permutation.permutation_utils import _get_ordered_swap

# This qasm should be identical to the one produced when permutation
# was a circuit rather than a gate.
swaps = _get_ordered_swap(self.pattern)
gates_def = "".join(["swap q" + str(i) + ",q" + str(j) + "; " for i, j in swaps])
qubit_list = ",".join(["q" + str(n) for n in range(len(self.pattern))])
self._qasm_definition = (
"gate " + self._qasm_name + " " + qubit_list + " { " + gates_def + "}"
)
def _qasm2_decomposition(self):
# pylint: disable=cyclic-import
from qiskit.synthesis.permutation.permutation_utils import _get_ordered_swap

return self._qasmif(self._qasm_name)
name = f"permutation__{'_'.join(str(n) for n in self.pattern)}_"
out = QuantumCircuit(self.num_qubits, name=name)
for i, j in _get_ordered_swap(self.pattern):
out.swap(i, j)
return out.to_gate()
275 changes: 129 additions & 146 deletions qiskit/circuit/quantumcircuit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1620,7 +1620,7 @@ def qasm(
if self.num_parameters > 0:
raise QasmError("Cannot represent circuits with unbound parameters in OpenQASM 2.")

existing_gate_names = [
existing_gate_names = {
"barrier",
"measure",
"reset",
Expand Down Expand Up @@ -1666,12 +1666,11 @@ def qasm(
"c3x",
"c3sx", # This is the Qiskit gate name, but the qelib1.inc name is 'c3sqrtx'.
"c4x",
]

existing_composite_circuits: list[Instruction] = []
}

string_temp = self.header + "\n"
string_temp += self.extension_lib + "\n"
# Mapping of instruction name to a pair of the source for a definition, and an OQ2 string
# that includes the `gate` or `opaque` statement that defines the gate.
gates_to_define: OrderedDict[str, tuple[Instruction, str]] = OrderedDict()

regless_qubits = [bit for bit in self.qubits if not self.find_bit(bit).registers]
regless_clbits = [bit for bit in self.clbits if not self.find_bit(bit).registers]
Expand All @@ -1691,72 +1690,51 @@ def qasm(
for name, register in register_escaped_names.items()
for (idx, bit) in enumerate(register)
}
for name, reg in register_escaped_names.items():
string_temp += (
f"{'qreg' if isinstance(reg, QuantumRegister) else 'creg'} {name}[{reg.size}];\n"
)

register_definitions_qasm = "".join(
f"{'qreg' if isinstance(reg, QuantumRegister) else 'creg'} {name}[{reg.size}];\n"
for name, reg in register_escaped_names.items()
)
instruction_calls = []
for instruction in self._data:
operation = instruction.operation
if operation.name == "measure":
qubit = instruction.qubits[0]
clbit = instruction.clbits[0]
string_temp += "{} {} -> {};\n".format(
operation.qasm(),
bit_labels[qubit],
bit_labels[clbit],
)
instruction_qasm = f"measure {bit_labels[qubit]} -> {bit_labels[clbit]};"
elif operation.name == "reset":
string_temp += f"reset {bit_labels[instruction.qubits[0]]};\n"
instruction_qasm = f"reset {bit_labels[instruction.qubits[0]]};"
elif operation.name == "barrier":
qargs = ",".join(bit_labels[q] for q in instruction.qubits)
string_temp += "barrier;\n" if not qargs else f"barrier {qargs};\n"
instruction_qasm = "barrier;" if not qargs else f"barrier {qargs};"
else:
# Check instructions names or label are valid
escaped = _qasm_escape_name(operation.name, "gate_")
if escaped != operation.name:
operation = operation.copy(name=escaped)

# decompose gate using definitions if they are not defined in OpenQASM2
if operation.name not in existing_gate_names:
op_qasm_name = None
if operation.name == "permutation":
op_qasm_name = getattr(operation, "_qasm_name", None)
if op_qasm_name:
operation = operation.copy(name=op_qasm_name)

if operation not in existing_composite_circuits:
if operation.name in [
operation.name for operation in existing_composite_circuits
]:
# append operation id to name of operation copy to make it unique
operation = operation.copy(name=f"{operation.name}_{id(operation)}")

existing_composite_circuits.append(operation)

# Strictly speaking, the code below does not work for operations that
# do not have the "definition" method but require a complex (recursive)
# "_qasm_definition". Fortunately, right now we do not have any such operations.
if getattr(operation, "definition", None) is not None:
_add_sub_instruction_to_existing_composite_circuits(
operation, existing_gate_names, existing_composite_circuits
)
operation = _qasm2_define_custom_operation(
operation, existing_gate_names, gates_to_define
)

# Insert qasm representation of the original instruction
string_temp += "{} {};\n".format(
operation.qasm(),
",".join([bit_labels[j] for j in instruction.qubits + instruction.clbits]),
bits_qasm = ",".join(
bit_labels[j] for j in itertools.chain(instruction.qubits, instruction.clbits)
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why not instruction.qubits + instruction.clbits as before?

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Oh, no particular reason - I probably just didn't notice I'd done it during the rewrite. itertools.chain is the normal idiom I personally use, so I just wouldn't have thought about it.

)

# insert gate definitions
string_temp = _insert_composite_gate_definition_qasm(
string_temp, existing_composite_circuits, self.extension_lib
instruction_qasm = f"{operation.qasm()} {bits_qasm};"
instruction_calls.append(instruction_qasm)
instructions_qasm = "".join(f"{call}\n" for call in instruction_calls)
gate_definitions_qasm = "".join(f"{qasm}\n" for _, qasm in gates_to_define.values())

out = "".join(
(
self.header,
"\n",
self.extension_lib,
"\n",
gate_definitions_qasm,
register_definitions_qasm,
instructions_qasm,
)
)

if filename:
with open(filename, "w+", encoding=encoding) as file:
file.write(string_temp)
file.close()
file.write(out)

if formatted:
if not HAS_PYGMENTS:
Expand All @@ -1766,12 +1744,11 @@ def qasm(
pip_install="pip install pygments",
)
code = pygments.highlight(
string_temp, OpenQASMLexer(), Terminal256Formatter(style=QasmTerminalStyle)
out, OpenQASMLexer(), Terminal256Formatter(style=QasmTerminalStyle)
)
print(code)
return None
else:
return string_temp
return out

def draw(
self,
Expand Down Expand Up @@ -4886,28 +4863,100 @@ def _compare_parameters(param1: Parameter, param2: Parameter) -> int:
return _standard_compare(param1.name, param2.name)


def _add_sub_instruction_to_existing_composite_circuits(
instruction: Instruction,
existing_gate_names: list[str],
existing_composite_circuits: list[Instruction],
) -> None:
"""Recursively add undefined sub-instructions in the definition of the given
instruction to existing_composite_circuit list.
"""
for sub_instruction in instruction.definition:
sub_operation = sub_instruction.operation
# Check instructions names are valid
escaped = _qasm_escape_name(sub_operation.name, "gate_")
if escaped != sub_operation.name:
sub_operation = sub_operation.copy(name=escaped)
if (
sub_operation.name not in existing_gate_names
and sub_operation not in existing_composite_circuits
):
existing_composite_circuits.insert(0, sub_operation)
_add_sub_instruction_to_existing_composite_circuits(
sub_operation, existing_gate_names, existing_composite_circuits
# Used by the OQ2 exporter. Just needs to have enough parameters to support the largest standard
# (non-controlled) gate in our standard library. We have to use the same `Parameter` instances each
# time so the equality comparisons will work.
_QASM2_FIXED_PARAMETERS = [Parameter("param0"), Parameter("param1"), Parameter("param2")]


def _qasm2_define_custom_operation(operation, existing_gate_names, gates_to_define):
"""Extract a custom definition from the given operation, and append any necessary additional
subcomponents' definitions to the ``gates_to_define`` ordered dictionary.

Returns a potentially new :class:`.Instruction`, which should be used for the
:meth:`~.Instruction.qasm` call (it may have been renamed)."""
from qiskit.circuit import library as lib # pylint: disable=cyclic-import

if operation.name in existing_gate_names:
return operation

# Check instructions names or label are valid
escaped = _qasm_escape_name(operation.name, "gate_")
if escaped != operation.name:
operation = operation.copy(name=escaped)

# These are built-in gates that are known to be safe to construct by passing the correct number
# of `Parameter` instances positionally, and have no other information. We can't guarantee that
# if they've been subclassed, though. This is a total hack; ideally we'd be able to inspect the
# "calling" signatures of Qiskit `Gate` objects to know whether they're safe to re-parameterise.
known_good_parameterized = {
lib.PhaseGate,
lib.RGate,
lib.RXGate,
lib.RXXGate,
lib.RYGate,
lib.RYYGate,
lib.RZGate,
lib.RZXGate,
lib.RZZGate,
lib.XXMinusYYGate,
lib.XXPlusYYGate,
lib.UGate,
lib.U1Gate,
lib.U2Gate,
lib.U3Gate,
}

# In known-good situations we want to use a manually parametrised object as the source of the
# definition, but still continue to return the given object as the call-site object.
if type(operation) in known_good_parameterized:
parameterized_operation = type(operation)(*_QASM2_FIXED_PARAMETERS[: len(operation.params)])
elif hasattr(operation, "_qasm2_decomposition"):
new_op = operation._qasm2_decomposition()
parameterized_operation = operation = new_op.copy(
name=_qasm_escape_name(new_op.name, "gate_")
)
else:
parameterized_operation = operation

# If there's an _equal_ operation in the existing circuits to be defined, then our job is done.
previous_definition_source, _ = gates_to_define.get(operation.name, (None, None))
if parameterized_operation == previous_definition_source:
return operation

# Otherwise, if there's a naming clash, we need a unique name.
if operation.name in gates_to_define:
new_name = f"{operation.name}_{id(operation)}"
operation = operation.copy(name=new_name)
else:
new_name = operation.name

if parameterized_operation.params:
parameters_qasm = (
"(" + ",".join(f"param{i}" for i in range(len(parameterized_operation.params))) + ")"
)
else:
parameters_qasm = ""
qubits_qasm = ",".join(f"q{i}" for i in range(parameterized_operation.num_qubits))
parameterized_definition = getattr(parameterized_operation, "definition", None)
if parameterized_definition is None:
gates_to_define[new_name] = (
parameterized_operation,
f"opaque {new_name}{parameters_qasm} {qubits_qasm};",
)
else:
statements = []
qubit_labels = {bit: f"q{i}" for i, bit in enumerate(parameterized_definition.qubits)}
for instruction in parameterized_definition.data:
new_operation = _qasm2_define_custom_operation(
instruction.operation, existing_gate_names, gates_to_define
)
bits_qasm = ",".join(qubit_labels[q] for q in instruction.qubits)
statements.append(f"{new_operation.qasm()} {bits_qasm};")
body_qasm = " ".join(statements)
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definition_qasm = f"gate {new_name}{parameters_qasm} {qubits_qasm} {{ {body_qasm} }}"
gates_to_define[new_name] = (parameterized_operation, definition_qasm)
return operation


def _qasm_escape_name(name: str, prefix: str) -> str:
Expand Down Expand Up @@ -4940,72 +4989,6 @@ def _make_unique(name: str, already_defined: collections.abc.Set[str]) -> str:
return name


def _get_composite_circuit_qasm_from_instruction(instruction: Instruction) -> str:
"""Returns OpenQASM string composite circuit given an instruction.
The given instruction should be the result of composite_circuit.to_instruction()."""

if instruction.definition is None:
raise ValueError(f'Instruction "{instruction.name}" is not defined.')

gate_parameters = ",".join(["param%i" % num for num in range(len(instruction.params))])
qubit_parameters = ",".join(["q%i" % num for num in range(instruction.num_qubits)])
composite_circuit_gates = ""

definition = instruction.definition
definition_bit_labels = {
bit: idx for bits in (definition.qubits, definition.clbits) for idx, bit in enumerate(bits)
}
for sub_instruction in definition:
sub_operation = sub_instruction.operation
escaped = _qasm_escape_name(sub_operation.name, "gate_")
if escaped != sub_operation.name:
sub_operation = sub_operation.copy(name=escaped)

gate_qargs = ",".join(
"q%i" % index
for index in [definition_bit_labels[qubit] for qubit in sub_instruction.qubits]
)
composite_circuit_gates += f"{sub_operation.qasm()} {gate_qargs}; "

if composite_circuit_gates:
composite_circuit_gates = composite_circuit_gates.rstrip(" ")

if gate_parameters:
qasm_string = "gate {}({}) {} {{ {} }}".format(
instruction.name,
gate_parameters,
qubit_parameters,
composite_circuit_gates,
)
else:
qasm_string = "gate {} {} {{ {} }}".format(
instruction.name,
qubit_parameters,
composite_circuit_gates,
)

return qasm_string


def _insert_composite_gate_definition_qasm(
string_temp: str, existing_composite_circuits: list[Instruction], extension_lib: str
) -> str:
"""Insert composite gate definition QASM code right after extension library in the header"""

gate_definition_string = ""

# Generate gate definition string
for instruction in existing_composite_circuits:
if hasattr(instruction, "_qasm_definition"):
qasm_string = instruction._qasm_definition
else:
qasm_string = _get_composite_circuit_qasm_from_instruction(instruction)
gate_definition_string += "\n" + qasm_string

string_temp = string_temp.replace(extension_lib, f"{extension_lib}{gate_definition_string}")
return string_temp


def _bit_argument_conversion(specifier, bit_sequence, bit_set, type_) -> list[Bit]:
"""Get the list of bits referred to by the specifier ``specifier``.

Expand Down
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