From e6e0ffbce6ad360d9d444bf02f9bc20378c2ee30 Mon Sep 17 00:00:00 2001
From: ooooo <3164076421@qq.com>
Date: Thu, 22 May 2025 16:48:15 +0800
Subject: [PATCH] Fix accuracy diff for var&&std API

---
 python/paddle/tensor/stat.py                         |  6 ++++--
 test/legacy_test/test_zero_dim_sundry_dygraph_api.py | 10 +++++-----
 test/xpu/test_zero_dim_tensor_xpu.py                 | 11 ++++++-----
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/python/paddle/tensor/stat.py b/python/paddle/tensor/stat.py
index 97e62310c89d0..a69321f7ef874 100644
--- a/python/paddle/tensor/stat.py
+++ b/python/paddle/tensor/stat.py
@@ -14,6 +14,7 @@
 
 from __future__ import annotations
 
+import warnings
 from typing import TYPE_CHECKING, Literal
 
 from typing_extensions import TypeAlias, overload
@@ -29,7 +30,6 @@
 from ..common_ops_import import Variable
 from ..framework import LayerHelper, core
 from .math import _get_reduce_axis_with_tensor
-from .search import where
 
 if TYPE_CHECKING:
     from collections.abc import Sequence
@@ -204,7 +204,9 @@ def var(
     n = n.astype(dtype)
     if unbiased:
         one_const = paddle.ones([], x.dtype)
-        n = where(n > one_const, n - 1.0, one_const)
+        if paddle.in_dynamic_mode() and n <= one_const:
+            warnings.warn("Degrees of freedom is <= 0.", stacklevel=2)
+        n = n - 1.0
     n.stop_gradient = True
     out /= n
     if out.dtype != x.dtype:
diff --git a/test/legacy_test/test_zero_dim_sundry_dygraph_api.py b/test/legacy_test/test_zero_dim_sundry_dygraph_api.py
index 7c9df6ea78d41..2df72dd951d87 100644
--- a/test/legacy_test/test_zero_dim_sundry_dygraph_api.py
+++ b/test/legacy_test/test_zero_dim_sundry_dygraph_api.py
@@ -748,8 +748,8 @@ def test_std(self):
 
         self.assertEqual(out1.shape, [])
         self.assertEqual(out2.shape, [])
-        self.assertEqual(out1, 0)
-        self.assertEqual(out2, 0)
+        self.assertTrue(np.isnan(out1.numpy()))
+        self.assertTrue(np.isnan(out2.numpy()))
 
         self.assertEqual(x.grad.shape, [])
 
@@ -773,11 +773,11 @@ def test_var(self):
 
         self.assertEqual(out1.shape, [])
         self.assertEqual(out2.shape, [])
-        self.assertEqual(out1, 0)
-        self.assertEqual(out2, 0)
+        self.assertTrue(np.isnan(out1.numpy()))
+        self.assertTrue(np.isnan(out2.numpy()))
 
         self.assertEqual(x.grad.shape, [])
-        np.testing.assert_allclose(x.grad, 0)
+        self.assertTrue(np.isnan(x.grad.numpy()))
 
         # 2) x is ND
         x = paddle.rand([3, 5])
diff --git a/test/xpu/test_zero_dim_tensor_xpu.py b/test/xpu/test_zero_dim_tensor_xpu.py
index ac5e2df75b46f..20134b789d384 100644
--- a/test/xpu/test_zero_dim_tensor_xpu.py
+++ b/test/xpu/test_zero_dim_tensor_xpu.py
@@ -1074,10 +1074,11 @@ def test_std(self):
 
         self.assertEqual(out1.shape, [])
         self.assertEqual(out2.shape, [])
-        self.assertEqual(out1, 0)
-        self.assertEqual(out2, 0)
+        self.assertTrue(np.isnan(out1.numpy()))
+        self.assertTrue(np.isnan(out2.numpy()))
 
         self.assertEqual(x.grad.shape, [])
+        self.assertTrue(np.isnan(x.grad.numpy()))
 
         # 2) x is ND
         x = paddle.rand([3, 5])
@@ -1099,11 +1100,11 @@ def test_var(self):
 
         self.assertEqual(out1.shape, [])
         self.assertEqual(out2.shape, [])
-        self.assertEqual(out1, 0)
-        self.assertEqual(out2, 0)
+        self.assertTrue(np.isnan(out1.numpy()))
+        self.assertTrue(np.isnan(out2.numpy()))
 
         self.assertEqual(x.grad.shape, [])
-        np.testing.assert_allclose(x.grad, 0)
+        self.assertTrue(np.isnan(x.grad.numpy()))
 
         # 2) x is ND
         x = paddle.rand([3, 5])