remove empty block program (#56355)

* remove empty block program

* update implementation

python/paddle/distributed/passes/pass_utils.py

@@ -430,38 +430,75 @@ def _program_for_fthenb_and_1f1b(program):
     bwd_prog = Program()
     opt_prog = Program()
 
-    for idx, src_block in enumerate(program.blocks):
-        if idx == 0:
-            lr_block = lr_prog.block(0)
-            fwd_block = fwd_prog.block(0)
-            bwd_block = bwd_prog.block(0)
-            opt_block = opt_prog.block(0)
-        else:
-            lr_block = lr_prog._create_block(parent_idx=src_block.parent_idx)
-            fwd_block = fwd_prog._create_block(parent_idx=src_block.parent_idx)
-            bwd_block = bwd_prog._create_block(parent_idx=src_block.parent_idx)
-            opt_block = opt_prog._create_block(parent_idx=src_block.parent_idx)
-            lr_block._set_forward_block_idx(src_block.forward_block_idx)
-            fwd_block._set_forward_block_idx(src_block.forward_block_idx)
-            bwd_block._set_forward_block_idx(src_block.forward_block_idx)
-            opt_block._set_forward_block_idx(src_block.forward_block_idx)
-
-        # split the program based on the op_role
+    # split the program based on the op_role
+    def _split_ops(block):
+        lr_ops = []
+        fwd_ops = []
+        bwd_ops = []
+        opt_ops = []
         for op in src_block.ops:
             if is_lr_sched_op(op):
-                _create_program(src_block, lr_block, op)
+                lr_ops.append(op)
             if is_forward_op(op):
-                _create_program(src_block, fwd_block, op)
+                fwd_ops.append(op)
             elif is_backward_op(op):
-                _create_program(src_block, bwd_block, op)
+                bwd_ops.append(op)
             elif is_optimize_op(op):
-                _create_program(src_block, opt_block, op)
+                opt_ops.append(op)
             else:
                 raise ValueError(
                     "The op role: "
                     + str(op.attr('op_role'))
                     + " isn't one of LRSched, Forward, Backward or Optimizer."
                 )
+        return lr_ops, fwd_ops, bwd_ops, opt_ops
+
+    def _add_ops_into_block(src_block, dst_block, ops):
+        for op in ops:
+            _create_program(src_block, dst_block, op)
+
+    for idx, src_block in enumerate(program.blocks):
+        lr_ops, fwd_ops, bwd_ops, opt_ops = _split_ops(src_block)
+        if idx == 0:
+            lr_block = lr_prog.block(0)
+            _add_ops_into_block(src_block, lr_block, lr_ops)
+
+            fwd_block = fwd_prog.block(0)
+            _add_ops_into_block(src_block, fwd_block, fwd_ops)
+
+            bwd_block = bwd_prog.block(0)
+            _add_ops_into_block(src_block, bwd_block, bwd_ops)
+
+            opt_block = opt_prog.block(0)
+            _add_ops_into_block(src_block, opt_block, opt_ops)
+        else:
+            if len(lr_ops):
+                lr_block = lr_prog._create_block(
+                    parent_idx=src_block.parent_idx
+                )
+                lr_block._set_forward_block_idx(src_block.forward_block_idx)
+                _add_ops_into_block(src_block, lr_block, lr_ops)
+
+            if len(fwd_ops):
+                fwd_block = fwd_prog._create_block(
+                    parent_idx=src_block.parent_idx
+                )
+                fwd_block._set_forward_block_idx(src_block.forward_block_idx)
+                _add_ops_into_block(src_block, fwd_block, fwd_ops)
+
+            if len(bwd_ops):
+                bwd_block = bwd_prog._create_block(
+                    parent_idx=src_block.parent_idx
+                )
+                bwd_block._set_forward_block_idx(src_block.forward_block_idx)
+                _add_ops_into_block(src_block, bwd_block, bwd_ops)
+
+            if len(opt_ops):
+                opt_block = opt_prog._create_block(
+                    parent_idx=src_block.parent_idx
+                )
+                opt_block._set_forward_block_idx(src_block.forward_block_idx)
+                _add_ops_into_block(src_block, opt_block, opt_ops)
 
     lr_prog._sync_with_cpp()
     fwd_prog._sync_with_cpp()