Analyze the parallel efficiency.

        Return:
            :class:`ParallelEfficiency` object.

def pefficiency(self):
        """
        Analyze the parallel efficiency.

        Return:
            :class:`ParallelEfficiency` object.
        """
        timers = self.timers()

        # Number of CPUs employed in each calculation.
        ncpus = [timer.ncpus for timer in timers]

        # Find the minimum number of cpus used and its index in timers.
        min_idx = minloc(ncpus)
        min_ncpus = ncpus[min_idx]

        # Reference timer
        ref_t = timers[min_idx]

        # Compute the parallel efficiency (total and section efficiency)
        peff = {}
        ctime_peff = [(min_ncpus * ref_t.wall_time) / (t.wall_time * ncp) for (t, ncp) in zip(timers, ncpus)]
        wtime_peff = [(min_ncpus * ref_t.cpu_time) / (t.cpu_time * ncp) for (t, ncp) in zip(timers, ncpus)]
        n = len(timers)

        peff["total"] = {}
        peff["total"]["cpu_time"] = ctime_peff
        peff["total"]["wall_time"] = wtime_peff
        peff["total"]["cpu_fract"] = n * [100]
        peff["total"]["wall_fract"] = n * [100]

        for sect_name in self.section_names():
            #print(sect_name)
            ref_sect = ref_t.get_section(sect_name)
            sects = [t.get_section(sect_name) for t in timers]
            try:
                ctime_peff = [(min_ncpus * ref_sect.cpu_time) / (s.cpu_time * ncp) for (s, ncp) in zip(sects, ncpus)]
                wtime_peff = [(min_ncpus * ref_sect.wall_time) / (s.wall_time * ncp) for (s, ncp) in zip(sects, ncpus)]
            except ZeroDivisionError:
                ctime_peff = n * [-1]
                wtime_peff = n * [-1]

            assert sect_name not in peff
            peff[sect_name] = {}
            peff[sect_name]["cpu_time"] = ctime_peff
            peff[sect_name]["wall_time"] = wtime_peff

            peff[sect_name]["cpu_fract"] = [s.cpu_fract for s in sects]
            peff[sect_name]["wall_fract"] = [s.wall_fract for s in sects]

        return ParallelEfficiency(self._filenames, min_idx, peff)