I think you have error in _pool_backward function at this place:
dX = dpool_fun(dX_col, dout_col, pool_cache)
You set dX which is not used later.
UPD: IT actually not critical since dX_col is changed internally. So this line can be changed on:
dpool_fun(dX_col, dout_col, pool_cache)
or
dX_col= dpool_fun(dX_col, dout_col, pool_cache)
I think you have error in _pool_backward function at this place:
dX = dpool_fun(dX_col, dout_col, pool_cache)You set dX which is not used later.
UPD: IT actually not critical since dX_col is changed internally. So this line can be changed on:
dpool_fun(dX_col, dout_col, pool_cache)or
dX_col= dpool_fun(dX_col, dout_col, pool_cache)