[zerobubble]Support ZeroBubble Pipeline (#6034)

* [feat] add zerobubble pp (just a frame now); add POC test for dx_dw; add test for zerobubble;

* [feat] add dw test;

* [fix] fix weight not close;

* [update] update text;

* [feat] add test run_fwd_bwd automatic scheduling;

* [feat] split communication and calculation; fix pop empty send_bwd_buffer error;

* [feat] add test for p & p grad;

* [feat] add comments for ZBV func;

* [fix] rm useless assign and comments;

* [fix] fix ci test; add pytest;

* [feat] add run_fwd_bwd_with_microbatch  (replace input) & test; add p&p.grad assert close test & all pass;

* [feat] add apply v_schedule graph; p & p.grad assert err exist;

* [fix] update

* [feat] fix ci; add assert;

* [feat] fix poc format

* [feat] fix func name & ci; add comments;

* [fix] fix poc test; add comments in poc;

* [feat] add optim backward_b_by_grad

* [feat] fix optimizer bwd b & w; support return accum loss & output

* [feat] add fwd_bwd_step, run_fwd_only;

* [fix] fix optim bwd; add license for v_schedule; remove redundant attributes; fix schedule loop "while"--> "for"; add communication dict;

* [fix] fix communication_map;

* [feat] update test; rm comments;

* [fix] rm zbv in hybridplugin

* [fix] fix optim bwd;

* [fix] fix optim bwd;

* [fix] rm output.data after send fwd;

* [fix] fix bwd step if condition; remove useless comments and format info;

* [fix] fix detach output & release output;

* [fix] rm requir_grad for output;

* [fix] fix requir grad position and detach position and input&output local buffer append position;

* [feat] add memory assertation;

* [fix] fix mem check;

* [fix] mem assertation'

* [fix] fix mem assertation

* [fix] fix mem; use a new model shape; only assert mem less and equal than theo;

* [fix] fix model zoo import;

* [fix] fix redundant detach & clone; add buffer assertation in the end;

* [fix] add output_obj_grad assert None at bwd b step; replace input_obj.require_grad_ with treemap;

* [fix] update optim state dict assert (include param group & state); fix mem assert after add optim;

* [fix] add testcase with microbatch 4;

colossalai/interface/optimizer.py

@@ -55,8 +55,25 @@ class OptimizerWrapper:
         """
         loss.backward(*args, **kwargs)
 
-    def backward_by_grad(self, tensor: Tensor, grad: Tensor):
-        torch.autograd.backward(tensor, grad)
+    def backward_by_grad(self, tensor: Tensor, grad: Tensor, inputs: Tensor = None, retain_graph: bool = False):
+        """
+        Performs a backward pass for dx or dw,
+        for dx, we only calculate dx = w*dy here
+        for dw, we only calculate dw = x*dy here
+
+        Args:
+            tensor (Tensor): y or loss of current chunk;
+            grad_tensors (Tensor): dy of current chunk;
+            input_obj (Tensor): for dx, input_obj is x of current chunk;
+                                for dw, input_obj is w of current chunk;
+            retain_graph (bool): default to be True, we retain graph in backward_b
+        """
+        torch.autograd.backward(
+            tensors=tensor,
+            grad_tensors=grad,
+            inputs=inputs,
+            retain_graph=retain_graph,
+        )
 
     def state_dict(self):
         """