[Fix] No Shuffling for `val_dataloader` (#423)

Validation should not have shuffling.

verl/trainer/fsdp_sft_trainer.py

@@ -167,7 +167,7 @@ class FSDPSFTTrainer(object):
                                            drop_last=True)
 
         self.val_sampler = DistributedSampler(self.val_dataset,
-                                              shuffle=True,
+                                              shuffle=False,
                                               num_replicas=world_size,
                                               rank=rank,
                                               drop_last=True)

verl/trainer/ppo/ray_trainer.py

@@ -523,7 +523,7 @@ class RayPPOTrainer(object):
             # Validation datasets are sent to inference engines as a whole batch,
             # which will schedule the memory themselves.
             batch_size=len(self.val_dataset),
-            shuffle=True,
+            shuffle=False,
             drop_last=False,
             collate_fn=collate_fn)