[pytorch-vulkan] aten::.rand_like (#108086)

Summary:

Before implementing `aten::.randn_like` as requested (T152843033), I think it worth to extend `aten::rand_like` from existing `aten::uniform`, since they're so similar.

Test Plan:
```
[ttingchulin@6945.od /data/sandcastle/boxes/fbsource (rand_like)]$ LD_LIBRARY_PATH=third-party/swiftshader/lib/linux-x64/ buck run fbcode/mode/dev-nosan //xplat/caffe2:pt_vulkan_api_test_bin  -- --gtest_filter="*<test>*" eg.  -- --gtest_filter="*rand_like*"
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from VulkanAPITest
[ RUN      ] VulkanAPITest.rand_like
[       OK ] VulkanAPITest.rand_like (136 ms)
[----------] 1 test from VulkanAPITest (136 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (136 ms total)
[  PASSED  ] 1 test.

[ttingchulin@6945.od /data/sandcastle/boxes/fbsource (rand_like)]$ LD_LIBRARY_PATH=third-party/swiftshader/lib/linux-x64/ buck run fbcode/mode/dev-nosan //xplat/caffe2:pt_vulkan_api_test_bin  -- --gtest_filter="*<test>*" eg.  -- --gtest_filter="*uniform*"
Building: finished in 0.1 sec (100%) 329/329 jobs, 0/329 updated
  Total time: 0.1 sec
BUILD SUCCEEDED
Running main() from xplat/third-party/gmock/googletest-1.12.1/googletest/src/gtest_main.cc
Note: Google Test filter = *uniform*
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from VulkanAPITest
[ RUN      ] VulkanAPITest.uniform
[       OK ] VulkanAPITest.uniform (131 ms)
[----------] 1 test from VulkanAPITest (131 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (131 ms total)
[  PASSED  ] 1 test.

[ttingchulin@6945.od /data/sandcastle/boxes/fbsource (rand_like)]$ LD_LIBRARY_PATH=third-party/swiftshader/lib/linux-x64/ buck run fbcode/mode/dev-nosan //xplat/caffe2:pt_vulkan_api_test_bin
ALL PASS
```

Reviewed By: yipjustin

Differential Revision: D48710273

aten/src/ATen/native/vulkan/ops/Random.cpp

@@ -14,9 +14,9 @@ using namespace api::utils;
 
 Tensor& uniform_(
     Tensor& self,
-    double from,
-    double to,
-    c10::optional<at::Generator> /* not implemented */) {
+    const double from,
+    const double to,
+    const c10::optional<at::Generator> /* not implemented */) {
   TORCH_CHECK(
       self.is_vulkan(),
       "Vulkan: In-place operator is only supported on Vulkan tensors.");
@@ -57,10 +57,25 @@ Tensor& uniform_(
   return self;
 }
 
+Tensor rand_like(
+    const at::Tensor& input_arg,
+    const c10::optional<c10::ScalarType> /* not implemented */,
+    const c10::optional<c10::Layout> /* not implemented */,
+    const c10::optional<c10::Device> /* not implemented */,
+    const c10::optional<bool> /* not implemented */,
+    const c10::optional<c10::MemoryFormat> /* not implemented */) {
+  // Returns a tensor with the same size as input that is filled with random
+  // numbers from a uniform distribution on the interval [0,1). To match the CPU
+  // implementation, we simplify the range to [0,1] and tolerate the small
+  // chance of 1 being sampled.
+  return input_arg.clone().detach().uniform_(0.0, 1.0);
+}
+
 #ifdef USE_VULKAN_API
 
 TORCH_LIBRARY_IMPL(aten, Vulkan, m) {
   m.impl(TORCH_SELECTIVE_NAME("aten::uniform_"), TORCH_FN(uniform_));
+  m.impl(TORCH_SELECTIVE_NAME("aten::rand_like"), TORCH_FN(rand_like));
 }
 
 #endif /* USE_VULKAN_API */

aten/src/ATen/test/vulkan_api_test.cpp

@@ -3921,16 +3921,9 @@ TEST_F(VulkanAPITest, sum_dim_keepdim_4d) {
   test_sum_dim({9, 5, 7, 11}, {-2, -3, -4}, true);
 }
 
-TEST_F(VulkanAPITest, uniform) {
-  float a_min = -8.2f;
-  float a_max = -1.4f;
-
-  auto a_vulkan =
-      at::rand({8, 7, 12, 10}, at::device(at::kCPU).dtype(at::kFloat)).vulkan();
-  a_vulkan.uniform_(a_min, a_max);
+void test_uniform(at::Tensor a_vulkan, const float a_min, const float a_max) {
   auto a_cpu = a_vulkan.cpu();
-
-  ASSERT_TRUE(a_cpu.max().item<float>() < a_max);
+  ASSERT_TRUE(a_cpu.max().item<float>() <= a_max);
   ASSERT_TRUE(a_cpu.min().item<float>() >= a_min);
 
   // Verify range, also perform a loose check with on histogram distribution.
@@ -3956,6 +3949,26 @@ TEST_F(VulkanAPITest, uniform) {
       (expected_per_bin * 0.05));
 }
 
+TEST_F(VulkanAPITest, uniform) {
+  float a_min = -8.2f;
+  float a_max = -1.4f;
+  auto a_vulkan =
+      at::rand({8, 7, 12, 10}, at::device(at::kCPU).dtype(at::kFloat)).vulkan();
+  a_vulkan.uniform_(a_min, a_max);
+  test_uniform(a_vulkan, a_min, a_max);
+}
+
+TEST_F(VulkanAPITest, rand_like) {
+  float a_min = 0.0f;
+  float a_max = 1.0f;
+  auto a_vulkan =
+      at::zeros({8, 7, 12, 10}, at::device(at::kCPU).dtype(at::kFloat)).vulkan();
+  const auto out_vulkan = at::rand_like(a_vulkan);
+  // verify that the input are still all zeros (not in-place)
+  ASSERT_TRUE(at::mean(a_vulkan.cpu()).item<float>() == 0.0);
+  test_uniform(out_vulkan, a_min, a_max);
+}
+
 void test_t(const at::IntArrayRef input_shape) {
   const auto in_cpu = at::rand(input_shape, at::device(at::kCPU).dtype(at::kFloat));
   const auto out_cpu = at::t(in_cpu);