Theano consider constant op

consider_constant.py

import theano
import theano.tensor as T
from theano.tensor.opt import register_canonicalize

class ConsiderConstant(theano.compile.ViewOp):
    def grad(self, args, g_outs):
        return [T.zeros_like(g_out) for g_out in g_outs]

consider_constant = ConsiderConstant()
register_canonicalize(theano.gof.OpRemove(consider_constant), name='remove_consider_constant')

# TODO: implement w.r.t.?

Example:

g = T.grad((x * consider_constant(x)).sum(), x)
=> gradient is x, not 2*x, as the second x is treated as a constant.