def moment_by_moment_schedule(device: Device, circuit: Circuit):
"""Returns a schedule aligned with the moment structure of the Circuit.
This method attempts to create a schedule in which each moment of a circuit
is scheduled starting at the same time. Given the constraints of the
given device, such a schedule may not be possible, in this case the
the method will raise a ValueError with a description of the conflict.
The schedule that is produced will take each moments and schedule the
operations in this moment in a time slice of length equal to the maximum
time of an operation in the moment.
Returns:
A Schedule for the circuit.
Raises:
ValueError: if the scheduling cannot be done.
"""
schedule = Schedule(device)
t = Timestamp()
for moment in circuit.moments:
if not moment.operations:
continue
for op in moment.operations:
scheduled_op = ScheduledOperation.op_at_on(op, t, device)
# Raises a ValueError describing the problem if this cannot be
# scheduled.
schedule.include(scheduled_operation=scheduled_op)
# Raises ValueError at first sign of a device conflict.
device.validate_scheduled_operation(schedule, scheduled_op)
# Increment time for next moment by max of ops during this moment.
max_duration = max(device.duration_of(op) for op in moment.operations)
t += max_duration
return schedule
def op_at_on(operation: ops.Operation,
time: Timestamp,
device: Device):
"""Creates a scheduled operation with a device-determined duration."""
return ScheduledOperation(time,
device.duration_of(operation),
operation)
def op_at_on(operation: ops.Operation,
time: Timestamp,
device: Device):
"""Creates a scheduled operation with a device-determined duration."""
return ScheduledOperation(time,
device.duration_of(operation),
operation)
def program_as_schedule(self,
program: Union[Circuit, Schedule],
device: Device = None) -> Schedule:
if isinstance(program, Circuit):
device = device or UnconstrainedDevice
circuit_copy = Circuit(program.moments)
ConvertToXmonGates().optimize_circuit(circuit_copy)
DropEmptyMoments().optimize_circuit(circuit_copy)
device.validate_circuit(circuit_copy)
return moment_by_moment_schedule(device, circuit_copy)
elif isinstance(program, Schedule):
if device:
raise ValueError(
'Device can not be provided when running a schedule.')
return program
else:
raise TypeError('Unexpected program type.')