update SA comp check to fix torch-cpu issue (#631)

op_builder/sparse_attn.py

@@ -25,6 +25,18 @@ class SparseAttnBuilder(OpBuilder):
         command_status = list(map(self.command_exists, required_commands))
         deps_compatible = all(command_status)
 
+        # torch-cpu will not have a cuda version
+        if torch.version.cuda is None:
+            cuda_compatible = False
+            self.warning(f"{self.NAME} cuda is not available from torch")
+        else:
+            major, minor = torch.version.cuda.split('.')[:2]
+            cuda_compatible = int(major) == 10 and int(minor) >= 1
+            if not cuda_compatible:
+                self.warning(
+                    f"{self.NAME} requires CUDA version 10.1+, does not currently support >=11 or <10.1"
+                )
+
         TORCH_MAJOR = int(torch.__version__.split('.')[0])
         TORCH_MINOR = int(torch.__version__.split('.')[1])
         torch_compatible = TORCH_MAJOR == 1 and TORCH_MINOR >= 5
@@ -33,4 +45,5 @@ class SparseAttnBuilder(OpBuilder):
                 f'{self.NAME} requires a torch version >= 1.5 but detected {TORCH_MAJOR}.{TORCH_MINOR}'
             )
 
-        return super().is_compatible() and deps_compatible and torch_compatible
+        return super().is_compatible(
+        ) and deps_compatible and torch_compatible and cuda_compatible