X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FRandom.h;h=e74d64b14dcf441c944483092f7a6b8491fb4f2d;hp=0962d07e15445c6ae47385585073d680ea87ceed;hb=35054c8b8eefa0abaded33ff4150d195c9bf0e80;hpb=015f5dc525643e73a517cf22046ded72c5b6224d

diff --git a/folly/Random.h b/folly/Random.h
index 0962d07e..e74d64b1 100644
--- a/folly/Random.h
+++ b/folly/Random.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,10 +17,13 @@
 #pragma once
 #define FOLLY_RANDOM_H_
 
-#include <type_traits>
+#include <array>
+#include <cstdint>
 #include <random>
-#include <stdint.h>
+#include <type_traits>
+
 #include <folly/Portability.h>
+#include <folly/Traits.h>
 
 #if FOLLY_HAVE_EXTRANDOM_SFMT19937
 #include <ext/random>
@@ -40,7 +43,7 @@ namespace folly {
  * However, if you are worried about performance, you can memoize the TLS
  * lookups that get the per thread state by manually using this class:
  *
- * ThreadLocalPRNG rng = Random::threadLocalPRNG()
+ * ThreadLocalPRNG rng;
  * for (...) {
  *   Random::rand32(rng);
  * }
@@ -65,9 +68,9 @@ class ThreadLocalPRNG {
 
   ThreadLocalPRNG();
 
- private:
   class LocalInstancePRNG;
 
+ private:
   static result_type getImpl(LocalInstancePRNG* local);
   LocalInstancePRNG* local_;
 };
@@ -133,25 +136,22 @@ class Random {
    * Returns a random uint32_t
    */
   static uint32_t rand32() {
-    ThreadLocalPRNG prng;
-    return rand32(prng);
+    return rand32(ThreadLocalPRNG());
   }
 
   /**
    * Returns a random uint32_t given a specific RNG
    */
   template <class RNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint32_t rand32(RNG rng) {
-    uint32_t r = rng.operator()();
-    return r;
+  static uint32_t rand32(RNG&& rng) {
+    return rng();
   }
 
   /**
    * Returns a random uint32_t in [0, max). If max == 0, returns 0.
    */
   static uint32_t rand32(uint32_t max) {
-    ThreadLocalPRNG prng;
-    return rand32(max, prng);
+    return rand32(0, max, ThreadLocalPRNG());
   }
 
   /**
@@ -159,84 +159,123 @@ class Random {
    * If max == 0, returns 0.
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint32_t rand32(uint32_t max, RNG rng = RNG()) {
-    if (max == 0) {
-      return 0;
-    }
-
-    return std::uniform_int_distribution<uint32_t>(0, max - 1)(rng);
+  static uint32_t rand32(uint32_t max, RNG&& rng) {
+    return rand32(0, max, rng);
   }
 
   /**
    * Returns a random uint32_t in [min, max). If min == max, returns 0.
    */
+  static uint32_t rand32(uint32_t min, uint32_t max) {
+    return rand32(min, max, ThreadLocalPRNG());
+  }
+
+  /**
+   * Returns a random uint32_t in [min, max) given a specific RNG.
+   * If min == max, returns 0.
+   */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint32_t rand32(uint32_t min, uint32_t max, RNG rng = RNG()) {
+  static uint32_t rand32(uint32_t min, uint32_t max, RNG&& rng) {
     if (min == max) {
       return 0;
     }
-
     return std::uniform_int_distribution<uint32_t>(min, max - 1)(rng);
   }
 
+  /**
+   * Returns a random uint64_t
+   */
+  static uint64_t rand64() {
+    return rand64(ThreadLocalPRNG());
+  }
+
   /**
    * Returns a random uint64_t
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint64_t rand64(RNG rng = RNG()) {
-    return ((uint64_t) rng() << 32) | rng();
+  static uint64_t rand64(RNG&& rng) {
+    return ((uint64_t)rng() << 32) | rng();
+  }
+
+  /**
+   * Returns a random uint64_t in [0, max). If max == 0, returns 0.
+   */
+  static uint64_t rand64(uint64_t max) {
+    return rand64(0, max, ThreadLocalPRNG());
   }
 
   /**
    * Returns a random uint64_t in [0, max). If max == 0, returns 0.
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint64_t rand64(uint64_t max, RNG rng = RNG()) {
-    if (max == 0) {
-      return 0;
-    }
+  static uint64_t rand64(uint64_t max, RNG&& rng) {
+    return rand64(0, max, rng);
+  }
 
-    return std::uniform_int_distribution<uint64_t>(0, max - 1)(rng);
+  /**
+   * Returns a random uint64_t in [min, max). If min == max, returns 0.
+   */
+  static uint64_t rand64(uint64_t min, uint64_t max) {
+    return rand64(min, max, ThreadLocalPRNG());
   }
 
   /**
    * Returns a random uint64_t in [min, max). If min == max, returns 0.
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static uint64_t rand64(uint64_t min, uint64_t max, RNG rng = RNG()) {
+  static uint64_t rand64(uint64_t min, uint64_t max, RNG&& rng) {
     if (min == max) {
       return 0;
     }
-
     return std::uniform_int_distribution<uint64_t>(min, max - 1)(rng);
   }
 
+  /**
+   * Returns true 1/n of the time. If n == 0, always returns false
+   */
+  static bool oneIn(uint32_t n) {
+    return oneIn(n, ThreadLocalPRNG());
+  }
+
   /**
    * Returns true 1/n of the time. If n == 0, always returns false
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static bool oneIn(uint32_t n, ValidRNG<RNG> rng = RNG()) {
+  static bool oneIn(uint32_t n, RNG&& rng) {
     if (n == 0) {
       return false;
     }
+    return rand32(0, n, rng) == 0;
+  }
 
-    return rand32(n, rng) == 0;
+  /**
+   * Returns a double in [0, 1)
+   */
+  static double randDouble01() {
+    return randDouble01(ThreadLocalPRNG());
   }
 
   /**
    * Returns a double in [0, 1)
    */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static double randDouble01(RNG rng = RNG()) {
-    return std::generate_canonical<double, std::numeric_limits<double>::digits>
-      (rng);
+  static double randDouble01(RNG&& rng) {
+    return std::generate_canonical<double, std::numeric_limits<double>::digits>(
+        rng);
+  }
+
+  /**
+    * Returns a double in [min, max), if min == max, returns 0.
+    */
+  static double randDouble(double min, double max) {
+    return randDouble(min, max, ThreadLocalPRNG());
   }
 
   /**
     * Returns a double in [min, max), if min == max, returns 0.
     */
   template <class RNG = ThreadLocalPRNG, class /* EnableIf */ = ValidRNG<RNG>>
-  static double randDouble(double min, double max, RNG rng = RNG()) {
+  static double randDouble(double min, double max, RNG&& rng) {
     if (std::fabs(max - min) < std::numeric_limits<double>::epsilon()) {
       return 0;
     }
@@ -255,6 +294,6 @@ inline uint32_t randomNumberSeed() {
   return Random::rand32();
 }
 
-}
+} // namespace folly
 
 #include <folly/Random-inl.h>