qiskit/circuit/quantumcircuit.py
def num_connected_components(self, unitary_only=False):
        """How many non-entangled subcircuits can the circuit be factored to.

        Args:
            unitary_only (bool): Compute only unitary part of graph.

        Returns:
            int: Number of connected components in circuit.
        """
        # Convert registers to ints (as done in depth).
        reg_offset = 0
        reg_map = {}

        if unitary_only:
            regs = self.qregs
        else:
            regs = self.qregs+self.cregs

        for reg in regs:
            reg_map[reg.name] = reg_offset
            reg_offset += reg.size
        # Start with each qubit or cbit being its own subgraph.
        sub_graphs = [[bit] for bit in range(reg_offset)]

        num_sub_graphs = len(sub_graphs)

        # Here we are traversing the gates and looking to see
        # which of the sub_graphs the gate joins together.
        for instr, qargs, cargs in self.data:
            if unitary_only:
                args = qargs
                num_qargs = len(args)
            else:
                args = qargs+cargs
                num_qargs = len(args) + (1 if instr.control else 0)

            if num_qargs >= 2 and instr.name not in ['barrier', 'snapshot']:
                graphs_touched = []
                num_touched = 0
                # Controls necessarily join all the cbits in the
                # register that they use.
                if instr.control and not unitary_only:
                    creg = instr.control[0]
                    creg_int = reg_map[creg.name]
                    for coff in range(creg.size):
                        temp_int = creg_int+coff
                        for k in range(num_sub_graphs):
                            if temp_int in sub_graphs[k]:
                                graphs_touched.append(k)
                                num_touched += 1
                                break

                for item in args:
                    reg_int = reg_map[item[0].name]+item[1]
                    for k in range(num_sub_graphs):
                        if reg_int in sub_graphs[k]:
                            if k not in graphs_touched:
                                graphs_touched.append(k)
                                num_touched += 1
                                break

                # If the gate touches more than one subgraph
                # join those graphs together and return
                # reduced number of subgraphs
                if num_touched > 1:
                    connections = []
                    for idx in graphs_touched:
                        connections.extend(sub_graphs[idx])
                    _sub_graphs = []
                    for idx in range(num_sub_graphs):
                        if idx not in graphs_touched:
                            _sub_graphs.append(sub_graphs[idx])
                    _sub_graphs.append(connections)
                    sub_graphs = _sub_graphs
                    num_sub_graphs -= (num_touched-1)
            # Cannot go lower than one so break
            if num_sub_graphs == 1:
                break
        return num_sub_graphs
def num_connected_components(self, unitary_only=False):
        # Convert registers to ints (as done in depth).
        reg_offset = 0
        reg_map = {}

        if unitary_only:
            regs = self.qregs
        else:
            regs = self.qregs+self.cregs

        for reg in regs:
            reg_map[reg.name] = reg_offset
            reg_offset += reg.size
        # Start with each qubit or cbit being its own subgraph.
        sub_graphs = [[bit] for bit in range(reg_offset)]

        num_sub_graphs = len(sub_graphs)

        # Here we are traversing the gates and looking to see
        # which of the sub_graphs the gate joins together.
        for instr, qargs, cargs in self.data:
            if unitary_only:
                args = qargs
                num_qargs = len(args)
            else:
                args = qargs+cargs
                num_qargs = len(args) + (1 if instr.control else 0)

            if num_qargs >= 2 and instr.name not in ['barrier', 'snapshot']:
                graphs_touched = []
                num_touched = 0
                # Controls necessarily join all the cbits in the
                # register that they use.
                if instr.control and not unitary_only:
                    creg = instr.control[0]
                    creg_int = reg_map[creg.name]
                    for coff in range(creg.size):
                        temp_int = creg_int+coff
                        for k in range(num_sub_graphs):
                            if temp_int in sub_graphs[k]:
                                graphs_touched.append(k)
                                num_touched += 1
                                break

                for item in args:
                    reg_int = reg_map[item[0].name]+item[1]
                    for k in range(num_sub_graphs):
                        if reg_int in sub_graphs[k]:
                            if k not in graphs_touched:
                                graphs_touched.append(k)
                                num_touched += 1
                                break

                # If the gate touches more than one subgraph
                # join those graphs together and return
                # reduced number of subgraphs
                if num_touched > 1:
                    connections = []
                    for idx in graphs_touched:
                        connections.extend(sub_graphs[idx])
                    _sub_graphs = []
                    for idx in range(num_sub_graphs):
                        if idx not in graphs_touched:
                            _sub_graphs.append(sub_graphs[idx])
                    _sub_graphs.append(connections)
                    sub_graphs = _sub_graphs
                    num_sub_graphs -= (num_touched-1)
            # Cannot go lower than one so break
            if num_sub_graphs == 1:
                break
        return num_sub_graphs
def num_connected_components ( self , unitary_only = False ) : # Convert registers to ints (as done in depth). reg_offset = 0 reg_map = { } if unitary_only : regs = self . qregs else : regs = self . qregs + self . cregs for reg in regs : reg_map [ reg . name ] = reg_offset reg_offset += reg . size # Start with each qubit or cbit being its own subgraph. sub_graphs = [ [ bit ] for bit in range ( reg_offset ) ] num_sub_graphs = len ( sub_graphs ) # Here we are traversing the gates and looking to see # which of the sub_graphs the gate joins together. for instr , qargs , cargs in self . data : if unitary_only : args = qargs num_qargs = len ( args ) else : args = qargs + cargs num_qargs = len ( args ) + ( 1 if instr . control else 0 ) if num_qargs >= 2 and instr . name not in [ 'barrier' , 'snapshot' ] : graphs_touched = [ ] num_touched = 0 # Controls necessarily join all the cbits in the # register that they use. if instr . control and not unitary_only : creg = instr . control [ 0 ] creg_int = reg_map [ creg . name ] for coff in range ( creg . size ) : temp_int = creg_int + coff for k in range ( num_sub_graphs ) : if temp_int in sub_graphs [ k ] : graphs_touched . append ( k ) num_touched += 1 break for item in args : reg_int = reg_map [ item [ 0 ] . name ] + item [ 1 ] for k in range ( num_sub_graphs ) : if reg_int in sub_graphs [ k ] : if k not in graphs_touched : graphs_touched . append ( k ) num_touched += 1 break # If the gate touches more than one subgraph # join those graphs together and return # reduced number of subgraphs if num_touched > 1 : connections = [ ] for idx in graphs_touched : connections . extend ( sub_graphs [ idx ] ) _sub_graphs = [ ] for idx in range ( num_sub_graphs ) : if idx not in graphs_touched : _sub_graphs . append ( sub_graphs [ idx ] ) _sub_graphs . append ( connections ) sub_graphs = _sub_graphs num_sub_graphs -= ( num_touched - 1 ) # Cannot go lower than one so break if num_sub_graphs == 1 : break return num_sub_graphs
How many non-entangled subcircuits can the circuit be factored to.

        Args:
            unitary_only (bool): Compute only unitary part of graph.

        Returns:
            int: Number of connected components in circuit.
How many non - entangled subcircuits can the circuit be factored to .