Generates ILP problem to be solved by glpsol

generate.py

from collections import defaultdict

def name1(i):
    return chr(ord('A')+i)

def name2(x, n):
    return ''.join(name1(i) for i in xrange(n) if x&(1<<i))

def print_model(L, U, n, G):
    for x in range(1, 2**n):
        print 'var c{}, integer, >=0;'.format(name2(x, n))

    print
    for i in range(n):
        for j in range(i+1, n):
            a, b = U if G[i][j] else L
            mult = -1 if G[i][j] else 1
            
            line = []
            for x in range(2**n):
                coeff = 0
                if x&(1<<i) and x&(1<<j): coeff += mult * b
                if x&(1<<i) or x&(1<<j): coeff -= mult * a
                line.append(coeff)
            expr = ' + '.join('{}*c{}'.format(x, name2(i, n)) for i,x in enumerate(line) if x)
            print "s.t. s{}{}: {} <= 0;".format(name1(i), name1(j), expr)

    print
    for i in range(n):
        expr = ' + '.join('c{}'.format(name2(x, n)) for x in range(2**n) if x&(1<<i))
        print "s.t. m{}: {} >= 1;".format(name1(i), expr)

    print
    print "minimize z: {};".format(' + '.join('c' + name2(x, n) for x in range(1, 2**n)))
    
    print
    print 'solve;'
    print 'end;'


N = 6
G = defaultdict(lambda: defaultdict(lambda: False))
for i in range(0, 3):
    for j in range(3, 6):
        G[i][j] = G[j][i] = True

print_model((1,3), (1,2), N, G)