!16042 Fixes RNG_seed bug in StandardNormal operator

From: @huangbo77
Reviewed-by: @wuxuejian,@liangchenghui
Signed-off-by: @wuxuejian

mindspore/ccsrc/backend/kernel_compiler/cpu/random_cpu_kernel.cc

@@ -1,5 +1,5 @@
 /**
- * Copyright 2020 Huawei Technologies Co., Ltd
+ * Copyright 2020-2021 Huawei Technologies Co., Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,7 @@
  */
 #include <random>
 #include <thread>
+#include "common/thread_pool.h"
 #include "runtime/device/cpu/cpu_device_address.h"
 #include "backend/kernel_compiler/cpu/random_cpu_kernel.h"
 
@@ -41,11 +42,23 @@ void LaunchStandardNormal(int seed, int seed2, const std::vector<AddressPtr> &ou
   auto output = reinterpret_cast<float *>(outputs[0]->addr);
   size_t lens = outputs[0]->size / sizeof(float);
   std::normal_distribution<float> distribution;
-  auto task = [&](size_t start, size_t end) {
+  auto max_thread_num = common::ThreadPool::GetInstance().GetSyncRunThreadNum();
+  const float block_size = 128.0;
+  size_t thread_num = lens < block_size * max_thread_num ? std::ceil(lens / block_size) : max_thread_num;
+  std::vector<common::Task> tasks;
+  size_t start = 0;
+  size_t once_compute_size = (lens + thread_num - 1) / thread_num;
+  while (start < lens) {
+    size_t end = (start + once_compute_size) > lens ? lens : (start + once_compute_size);
     std::default_random_engine random_generator(++RNG_seed);
-    StandardNormal(output, distribution, random_generator, start, end);
-  };
-  CPUKernelUtils::ParallelFor(task, lens);
+    auto block = [&, start, end]() {
+      StandardNormal(output, distribution, random_generator, start, end);
+      return common::SUCCESS;
+    };
+    tasks.emplace_back(block);
+    start += once_compute_size;
+  }
+  common::ThreadPool::GetInstance().SyncRun(tasks);
 }
 
 void RandomCPUKernel::InitKernel(const CNodePtr &kernel_node) {