Adjust tolerance for fp16 exp op to handle reasonable calculation discrepancies

Author: leafs1

backends/xnnpack/test/ops/test_exp.py

@@ -21,7 +21,7 @@ def __init__(self):
         def forward(self, x):
             return torch.exp(x)
 
-    def run_exp_test(self, inputs):
+    def run_exp_test(self, inputs, rtol=1e-03, atol=1e-03):
         (
             Tester(self.Exp(), inputs)
             .export()
@@ -31,15 +31,13 @@ def run_exp_test(self, inputs):
             .check_not(["executorch_exir_dialects_edge__ops_aten_exp_default"])
             .to_executorch()
             .serialize()
-            .run_method_and_compare_outputs()
+            .run_method_and_compare_outputs(rtol=rtol, atol=atol)
         )
 
-    # TODO (leafs1): Fix flaky tests. Land fix asap
-    # and cherry-pick onto release/0.7 branch
-    @unittest.skip(reason="For float16, numerical discepancies are too high")
     def test_fp16_exp(self):
-        inputs = (torch.randn(20).to(torch.float16),)
-        self.run_exp_test(inputs)
+        for _ in range(1000):
+            inputs = (torch.randn(20).to(torch.float16),)
+            self.run_exp_test(inputs, rtol=2e-03, atol=2e-03)
 
     def test_fp32_exp(self):
         inputs = (torch.randn(20),)