Fix default num_stages values mismatch between Python frontend and MLIR. (triton-lang#5804)

Address the discrepancy between the default value of num_stages in the
Python frontend and the MLIR implementation. Previously, the values were
not aligned, which could cause inconsistencies in behavior across Python
Frontend and triton-opt.

This PR updates the default value of num_stages in the Python frontend
to match the ones used in MLIR.
-
[TritonGPUPipeline](https://github.com/triton-lang/triton/blob/032fa41a45847cdc00119ed3bdd5bc0adab9c938/include/triton/Dialect/TritonGPU/Transforms/Passes.td#L21)
-
[TritonGPUTestPipelineAssignLatencies](https://github.com/triton-lang/triton/blob/032fa41a45847cdc00119ed3bdd5bc0adab9c938/include/triton/Dialect/TritonGPU/Transforms/Passes.td#L58)
-
[TritonGPULoopScheduling](https://github.com/triton-lang/triton/blob/032fa41a45847cdc00119ed3bdd5bc0adab9c938/include/triton/Dialect/TritonGPU/Transforms/Passes.td#L266)

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Co-authored-by: pawelszczerbuk <[email protected]>

Author: 2 people

python/triton/runtime/autotuner.py

@@ -36,7 +36,7 @@ def __init__(
             'prune_num_stages_by'(optional): a function used to prune num_stages. It takes configs:List[Config] as its input, and returns pruned configs.
         """
         if not configs:
-            self.configs = [Config({}, num_warps=4, num_stages=2, num_ctas=1)]
+            self.configs = [Config({}, num_warps=4, num_stages=3, num_ctas=1)]
         else:
             self.configs = configs
         self.keys = key
@@ -269,7 +269,7 @@ class Config:
                     function are args.
     """
 
-    def __init__(self, kwargs, num_warps=4, num_stages=2, num_ctas=1, maxnreg=None, pre_hook=None):
+    def __init__(self, kwargs, num_warps=4, num_stages=3, num_ctas=1, maxnreg=None, pre_hook=None):
         self.kwargs = kwargs
         self.num_warps = num_warps
         self.num_ctas = num_ctas