[0-size Tensor No.144] Add 0-size Tensor support for paddle.nextafter API. (#73008)

* fix

* add test

* fix

* merge and fix

* fix error

* fix error

* fix error

Author: enkilee

paddle/phi/kernels/cpu/elementwise_kernel.cc

@@ -111,6 +111,10 @@ void NextafterKernel(const Context& dev_ctx,
                      const DenseTensor& x,
                      const DenseTensor& y,
                      DenseTensor* out) {
+  if (x.numel() == 0 || y.numel() == 0) {
+    dev_ctx.template Alloc<T>(out);
+    return;
+  }
   dev_ctx.template Alloc<T>(out);
   auto x_dims = x.dims();
   auto y_dims = y.dims();
@@ -210,5 +214,6 @@ PD_REGISTER_KERNEL(copysign,
                    double,
                    phi::dtype::float16,
                    phi::dtype::bfloat16) {}
+
 PD_REGISTER_KERNEL(
     nextafter, CPU, ALL_LAYOUT, phi::NextafterKernel, float, double) {}

paddle/phi/kernels/kps/elementwise_kernel.cu

@@ -201,6 +201,10 @@ void NextafterKernel(const Context& dev_ctx,
                      const DenseTensor& x,
                      const DenseTensor& y,
                      DenseTensor* out) {
+  if (x.numel() == 0 || y.numel() == 0) {
+    dev_ctx.template Alloc<T>(out);
+    return;
+  }
   std::vector<const DenseTensor*> inputs = {&x, &y};
   std::vector<DenseTensor*> outputs = {out};
   dev_ctx.template Alloc<T>(out);

test/legacy_test/test_nextafter_op.py

@@ -149,5 +149,31 @@ def init_shape(self):
         self.y_shape = (1,)
 
 
+class TestNextafterOPZeroDim1(TestNextafterOP):
+    def setUp(self):
+        self.op_type = "nextafter"
+        self.python_api = paddle.nextafter
+        self.init_dtype()
+
+        x = np.random.rand(0, 3, 2).astype(self.dtype)
+        y = np.random.rand(0, 3, 2).astype(self.dtype)
+        out = np.nextafter(x, y)
+        self.inputs = {'x': x, 'y': y}
+        self.outputs = {'out': out}
+
+
+class TestNextafterOPZeroDim2(TestNextafterOP):
+    def setUp(self):
+        self.op_type = "nextafter"
+        self.python_api = paddle.nextafter
+        self.init_dtype()
+
+        x = np.random.rand(4, 0, 2).astype(self.dtype)
+        y = np.random.rand(4, 0, 2).astype(self.dtype)
+        out = np.nextafter(x, y)
+        self.inputs = {'x': x, 'y': y}
+        self.outputs = {'out': out}
+
+
 if __name__ == "__main__":
     unittest.main()