import torch
from torch.autograd import Variable

x = Variable(torch.Tensor([1.1]),requires_grad=True)
y = Variable(torch.Tensor([1.2]),requires_grad=True)

# define two simple graphs

z = x * y

a = torch.exp(x)
b = torch.exp(a)

# how can i access x and y starting from z?

print "x:\n", z.grad_fn.saved_variables[0]
print "y:\n", z.grad_fn.saved_variables[1]

# how can i access a and x starting from b?
# db/da = b, so a doesn't appear in b.grad_fn.saved_varibles
# rather, b appears there

print "b:\n", b.grad_fn.saved_variables[0]

# similarily we have

print "a:\n", a.grad_fn.saved_variables[0]

# but what allows me to connect b <- a <- x ?