update autotuner input tensor random range (#2116)

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## 📌 Description

Update autotuner input tensor random range from [0,1) to [-5,5) for
larger range and closer to real tensor

## 🔍 Related Issues

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## Summary by CodeRabbit

* **Bug Fixes**
* Improved tensor initialization used during autotuning: values are now
drawn from a symmetric range around zero ([-5, 5]) with a more
uniform-like distribution, yielding more consistent and stable parameter
tuning results.

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settings.</sub>

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---------

Signed-off-by: jiahanc <173873397+jiahanc@users.noreply.github.com>

Author: jiahanc

flashinfer/autotuner.py

@@ -61,9 +61,9 @@ def __post_init__(self):
         # Set default tensor_initializers if not provided
         if self.tensor_initializers is None:
             self.tensor_initializers = [
-                lambda shapes, dtype, device: torch.randn(shapes, device=device).to(
-                    dtype
-                )
+                lambda shapes, dtype, device: (
+                    torch.rand(shapes, device=device) * 10 - 5
+                ).to(dtype)
                 for _ in range(len(self.input_idx))
             ]
 
@@ -761,8 +761,8 @@ def _create_tensor_like(
     def _prepare_input_tensors(
         self, profile: OptimizationProfile, inputs: List[torch.Tensor]
     ) -> List[torch.Tensor]:
-        default_initializer = lambda shapes, dtype, device: torch.rand(
-            shapes, device=device
+        default_initializer = lambda shapes, dtype, device: (
+            torch.rand(shapes, device=device) * 10 - 5
         ).to(dtype)
         tensors = []
         for i, p in enumerate(profile.shapes):