【Paddle Tensor 第二期 API支持 0-size Tensor】Fix frobenius_norm to support 0-size tensor (#72570)

* [Tensor] Fix frobenius_norm to support 0-size tensor

* [Tensor] Drop resize of fro-norm

* [Tensor] Import utils with non-relative path

* drop resize in gpu

Author: hanlintang

paddle/phi/kernels/gpu/frobenius_norm_kernel.cu

@@ -28,6 +28,11 @@ void FrobeniusNormKernel(const Context& dev_ctx,
                          bool keep_dim,
                          bool reduce_all,
                          DenseTensor* out) {
+  if (x.numel() == 0) {
+    dev_ctx.template Alloc<T>(out);
+    phi::funcs::SetConstant<Context, T>()(dev_ctx, out, static_cast<T>(0));
+    return;
+  }
   reduce_all = recompute_reduce_all(x, dims.GetData(), reduce_all);
   auto out_dtype = x.dtype();
   phi::Reduce<T, kps::AddFunctor, kps::SquareFunctor>(

paddle/phi/kernels/impl/frobenius_norm_kernel_impl.h

@@ -27,6 +27,11 @@ void FrobeniusNormKernel(const Context& ctx,
                          bool keep_dim,
                          bool reduce_all,
                          DenseTensor* out) {
+  if (x.numel() == 0) {
+    ctx.template Alloc<T>(out);
+    phi::funcs::SetConstant<Context, T>()(ctx, out, 0);
+    return;
+  }
   reduce_all = recompute_reduce_all(x, axis.GetData(), reduce_all);
   Reduce<Context, T, funcs::FrobeniusNormFunctor>(
       ctx, x, reduce_all, axis.GetData(), keep_dim, x.dtype(), out);