From 0cc7f02c823dbf177d42227bbaf66ee24b36eb84 Mon Sep 17 00:00:00 2001
From: Hans Dembinski <hans.dembinski@gmail.com>
Date: Sun, 17 Jul 2016 12:03:57 -0400
Subject: [PATCH] bug fix in speed test, and even faster binning

---
 README.md                        |  8 ++++----
 include/boost/histogram/axis.hpp | 26 ++++++++++++++++++++------
 test/check/speed_cpp.cpp         |  2 +-
 test/check/speed_root.cpp        |  2 +-
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index 1edc09ff..5f2dba35 100644
--- a/README.md
+++ b/README.md
@@ -165,10 +165,10 @@ distribution                                         uniform
 dimension                                    1D       3D       6D       1D       3D       6D
 ==========================================  =======  =======  =======  =======  =======  =======
 No. of fills                                12M      4M       2M       12M      4M       2M
-C++: ROOT  [t/s]                            0.127    0.199    0.185    0.168    0.143    0.179
-C++: boost/static_storage<unsigned> [t/s]   0.073    0.160    0.178    0.159    0.182    0.187
-Py: numpy [t/s]                             0.825    0.727    0.436    0.824    0.426    0.401
-Py: boost [t/s]                             0.209    0.229    0.192    0.207    0.194    0.168
+C++: ROOT  [t/s]                            0.13     0.19     0.18     0.14     0.18     0.20
+C++: boost/static_storage<unsigned> [t/s]   0.07     0.16     0.18     0.08     0.15     0.19
+Py: numpy [t/s]                             0.83     0.73     0.44     0.82     0.43     0.40
+Py: boost [t/s]                             0.21     0.23     0.19     0.21     0.19     0.17
 ==========================================  =======  =======  =======  =======  =======  =======
 ```
 
diff --git a/include/boost/histogram/axis.hpp b/include/boost/histogram/axis.hpp
index 62570efc..ae1ec3f2 100644
--- a/include/boost/histogram/axis.hpp
+++ b/include/boost/histogram/axis.hpp
@@ -7,6 +7,7 @@
 #ifndef _BOOST_HISTOGRAM_AXIS_HPP_
 #define _BOOST_HISTOGRAM_AXIS_HPP_
 
+#include <boost/histogram/detail/utility.hpp>
 #include <boost/variant.hpp>
 #include <boost/math/constants/constants.hpp>
 #include <type_traits>
@@ -25,7 +26,7 @@
 namespace boost {
 namespace histogram {
 
-/// common base class for most axes
+/// Common base class for most axes
 class axis_base {
 public:
   ///Returns the number of bins.
@@ -60,7 +61,7 @@ private:
   friend void serialize(Archive& ar, axis_base & base, unsigned version);
 };
 
-// mixin for real-valued axes
+/// Mixin for real-valued axes
 template <typename Derived>
 class real_axis {
 public:
@@ -79,7 +80,12 @@ public:
   }
 };
 
-///An axis for real-valued data and bins of equal width. Binning is a O(1) operation.
+/** Axis for binning real-valued data into equidistant bins
+  *
+  * This is the simplest and common binning strategy. The code
+  * was optimized with a profiled benchmark. 
+  * Binning is a O(1) operation.
+  */
 class regular_axis: public axis_base, public real_axis<regular_axis> {
 public:
   /** Constructor
@@ -107,11 +113,14 @@ public:
   regular_axis& operator=(const regular_axis&) = default;
   regular_axis& operator=(regular_axis&&) = default;
 
-  ///Returns the bin index for the passed argument (optimized code).
+  /// Returns the bin index for the passed argument (optimized code).
   inline int index(double x) const 
   {
     const double z = (x - min_) / delta_;
-    return std::signbit(z) ? -1 : z < bins() ? static_cast<int>(z) : bins();
+    const int i = static_cast<int>(z);
+    if (i > bins())
+      return bins();
+    return z >= 0.0 ? i : -1;
   }
 
   double operator[](int idx) const
@@ -138,7 +147,12 @@ private:
   friend void serialize(Archive& ar, regular_axis & axis ,unsigned version);
 };
 
-///An axis for real-valued angles. There are no overflow/underflow bins for this axis, since the axis is circular and wraps around after :math:`2 \pi`. Binning is a O(1) operation.
+/** Axis for real-valued angles
+  *
+  * There are no overflow/underflow bins for this axis,
+  * since the axis is circular and wraps around after :math:`2 \pi`.
+  * Binning is a O(1) operation.
+  */
 class polar_axis: public axis_base, public real_axis<polar_axis> {
 public:
   /** Constructor
diff --git a/test/check/speed_cpp.cpp b/test/check/speed_cpp.cpp
index 41296a06..7cadd70b 100644
--- a/test/check/speed_cpp.cpp
+++ b/test/check/speed_cpp.cpp
@@ -20,7 +20,7 @@ std::vector<double> random_array(unsigned n, int type) {
   std::vector<double> result(n);
   std::default_random_engine gen(1);
   if (type) { // type == 1
-    std::normal_distribution<> d(0.0, 0.3);
+    std::normal_distribution<> d(0.5, 0.3);
     for (auto& x : result)
       x = d(gen);
   }
diff --git a/test/check/speed_root.cpp b/test/check/speed_root.cpp
index 6290a1fb..772b9ea9 100644
--- a/test/check/speed_root.cpp
+++ b/test/check/speed_root.cpp
@@ -19,7 +19,7 @@ std::vector<double> random_array(unsigned n, int type) {
   std::vector<double> result(n);
   std::default_random_engine gen(1);
   if (type) { // type == 1
-    std::normal_distribution<> d(0.0, 0.3);
+    std::normal_distribution<> d(0.5, 0.3);
     for (auto& x : result)
       x = d(gen);
   }