weightsum

#!/usr/bin/env python

""" - Main program code for "weightsum" - A program to sum the
combinatorial weights of a list of Feynman diagrams.

This program is part of the feyncop/feyngen package.
"""

# See also: https://github.com/michibo/feyncop

# Author: Michael Borinsky
# Python3 port: Frédéric Chapoton

# Bugreports, comments, or suggestions are always welcome.
# For instance, via github or email

from fractions import Fraction
import argparse
import sys
# from math import *
# from stuff import *

import parsefg

# from graph import Graph
# from hopf_graph import HopfGraph


def main():
    """Main program section. Reads the options and parameters and starts the
        relevant subroutines."""

    parser = argparse.ArgumentParser(description='Sum the symmetry factors of a list of diagrams')
    parser.add_argument('-u', '--non_leg_fixed', dest='non_leg_fixed', action='store_true', help='Input non-leg-fixed graphs. I.e. external legs of graphs are not given with leg labels. (default: false)')
    parser.add_argument('-w', '--no_warning', dest='no_warning', action='store_true', help='Do not print warnings. (default: false)')
    args = parser.parse_args()

    string = ""
    try:
        string = next(sys.stdin)
    except StopIteration:
        return

    var_name, ev, el = parsefg.parse_var_name(string)
    if var_name:
        string = string[el:]

    graphs_fac = frozenset(parsefg.parse_input_lines(sys.stdin, None, string))

    sum_fac = Fraction(0, 1)
    for g, fac, ym in graphs_fac:
        g_sym = 0
        if not args.non_leg_fixed:
            g_sym = next(g.permute_external_edges()).unlabeled_graph.symmetry_factor
        else:
            g_sym = g.unlabeled_graph.symmetry_factor

        if Fraction(1, g_sym) != Fraction(fac, 1) and not args.no_warning:
            sys.stderr.write("Warning: %s doesn't have symmetry factor %s. It has %s. (Non-)Fixed legs?\n" % (g, fac, Fraction(1, g_sym)))
        sum_fac += fac

    print("%s" % sum_fac)


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        print("")
        print("Cancelled")