[fx] fix the discretize bug (#1506)

* [fx] fix wrong variable name in solver rotor

* [fx] fix wrong variable name in solver rotor

* code modification

* [fx] fix the discretize bug

colossalai/fx/passes/algorithms/ckpt_solver_rotor.py

@@ -142,8 +142,6 @@ def _construct_chain(node_dict: Dict[int, Node], data: torch.Tensor, mem_unit: i
 
     bwd_time.append(0)
 
-    fwd_time = _discretize(mem_unit, fwd_time)
-    bwd_time = _discretize(mem_unit, bwd_time)
     xbar_sizes = _discretize(mem_unit, xbar_sizes)
     x_sizes = _discretize(mem_unit, x_sizes)
     tmp_fwd = _discretize(mem_unit, tmp_fwd)