tensorflow: refine PhiloxRandomOp cost

Currently PhiloxRandomOp says that cost of generating
4 numbers is 4. This is way too far from reality.
RandomUniform cost is ~55 cycles per group, RandomNormal -- ~331 cycles,
TruncatedNormal -- ~392 cycles.
This new model predicts cost as 52, 320 and 400, respectively.
This is required for better parallelization in Shard.

random_op_test benchmarks do not show any change with current Shard.

TESTED:
  - passed opensource_build
http://ci.tensorflow.org/job/tensorflow-cl-multijob/1274/
Change: 121285968

2 files changed, 24 insertions, 0 deletions

diff --git a/tensorflow/core/lib/random/philox_random.h b/tensorflow/core/lib/random/philox_random.h
index dc8de09d2c..3e53eeae33 100644
--- a/tensorflow/core/lib/random/philox_random.h
+++ b/tensorflow/core/lib/random/philox_random.h
@@ -105,6 +105,8 @@ class PhiloxRandom {
   typedef uint32 ResultElementType;
   // The number of elements that will be returned.
   static const int kResultElementCount = 4;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 10;
 
   PHILOX_DEVICE_INLINE
   PhiloxRandom() {}
diff --git a/tensorflow/core/lib/random/random_distributions.h b/tensorflow/core/lib/random/random_distributions.h
index e81d25237c..c12e1b2b60 100644
--- a/tensorflow/core/lib/random/random_distributions.h
+++ b/tensorflow/core/lib/random/random_distributions.h
@@ -52,6 +52,8 @@ class UniformDistribution<Generator, Eigen::half> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 3;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -74,6 +76,8 @@ class UniformDistribution<Generator, float> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 3;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -96,6 +100,8 @@ class UniformDistribution<Generator, double> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount / 2;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 3;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -118,6 +124,8 @@ class UniformDistribution<Generator, int32> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 3;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -150,6 +158,8 @@ class UniformDistribution<Generator, int64> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount / 2;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 3;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -239,6 +249,8 @@ class NormalDistribution<Generator, Eigen::half> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 70;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -264,6 +276,8 @@ class NormalDistribution<Generator, float> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 70;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -286,6 +300,8 @@ class NormalDistribution<Generator, double> {
  public:
   // The number of elements that will be returned.
   static const int kResultElementCount = Generator::kResultElementCount / 2;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 70;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = false;
@@ -328,6 +344,8 @@ class TruncatedNormalDistribution<SingleSampleGenerator, Eigen::half> {
   // The number of elements that will be returned.
   static const int kResultElementCount =
       SingleSampleGenerator::kNativeElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 90;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = true;
@@ -369,6 +387,8 @@ class TruncatedNormalDistribution<SingleSampleGenerator, float> {
   // The number of elements that will be returned.
   static const int kResultElementCount =
       SingleSampleGenerator::kNativeElementCount;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 90;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = true;
@@ -412,6 +432,8 @@ class TruncatedNormalDistribution<SingleSampleGenerator, double> {
       (SingleSampleGenerator::kNativeElementCount > 1)
           ? SingleSampleGenerator::kNativeElementCount / 2
           : 1;
+  // Cost of generation of a single element (in cycles).
+  static const int kElementCost = 90;
   // Indicate that this distribution may take variable number of samples
   // during the runtime.
   static const bool kVariableSamplesPerOutput = true;