fix div 0 error of ftt.rfftfreq (#49955)

python/paddle/fft.py

@@ -1326,6 +1326,8 @@ def rfftfreq(n, d=1.0, dtype=None, name=None):
             #           [0.        , 0.66666669, 1.33333337])
 
     """
+    if d * n == 0:
+        raise ValueError("d or n should not be 0.")
 
     dtype = paddle.framework.get_default_dtype()
     val = 1.0 / (n * d)

python/paddle/fluid/tests/unittests/fft/test_fft.py

@@ -1860,6 +1860,23 @@ class TestRfftFreq(unittest.TestCase):
             )
 
 
+@place(DEVICES)
+@parameterize(
+    (TEST_CASE_NAME, 'n', 'd', 'dtype', 'expect_exception'),
+    [
+        ('test_with_0_0', 0, 0, 'float32', ValueError),
+        ('test_with_n_0', 20, 0, 'float32', ValueError),
+        ('test_with_0_d', 0, 20, 'float32', ValueError),
+    ],
+)
+class TestRfftFreqException(unittest.TestCase):
+    def test_rfftfreq2(self):
+        """Test fftfreq with d = 0"""
+        with paddle.fluid.dygraph.guard(self.place):
+            with self.assertRaises(self.expect_exception):
+                paddle.fft.rfftfreq(self.n, self.d, self.dtype)
+
+
 @place(DEVICES)
 @parameterize(
     (TEST_CASE_NAME, 'x', 'axes', 'dtype'),