diff --git a/bench/BenchTimer.h b/bench/BenchTimer.h
new file mode 100644
index 0000000..28e2bca
--- /dev/null
+++ b/bench/BenchTimer.h
@@ -0,0 +1,187 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
+// Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_BENCH_TIMERR_H
+#define EIGEN_BENCH_TIMERR_H
+
+#if defined(_WIN32) || defined(__CYGWIN__)
+# ifndef NOMINMAX
+#   define NOMINMAX
+#   define EIGEN_BT_UNDEF_NOMINMAX
+# endif
+# ifndef WIN32_LEAN_AND_MEAN
+#   define WIN32_LEAN_AND_MEAN
+#   define EIGEN_BT_UNDEF_WIN32_LEAN_AND_MEAN
+# endif
+# include <windows.h>
+#elif defined(__APPLE__)
+#include <CoreServices/CoreServices.h>
+#include <mach/mach_time.h>
+#else
+# include <unistd.h>
+#endif
+
+#include <Eigen/Core>
+
+namespace Eigen
+{
+
+enum {
+  CPU_TIMER = 0,
+  REAL_TIMER = 1
+};
+
+/** Elapsed time timer keeping the best try.
+  *
+  * On POSIX platforms we use clock_gettime with CLOCK_PROCESS_CPUTIME_ID.
+  * On Windows we use QueryPerformanceCounter
+  *
+  * Important: on linux, you must link with -lrt
+  */
+class BenchTimer
+{
+public:
+
+  BenchTimer()
+  {
+#if defined(_WIN32) || defined(__CYGWIN__)
+    LARGE_INTEGER freq;
+    QueryPerformanceFrequency(&freq);
+    m_frequency = (double)freq.QuadPart;
+#endif
+    reset();
+  }
+
+  ~BenchTimer() {}
+
+  inline void reset()
+  {
+    m_bests.fill(1e9);
+    m_worsts.fill(0);
+    m_totals.setZero();
+  }
+  inline void start()
+  {
+    m_starts[CPU_TIMER]  = getCpuTime();
+    m_starts[REAL_TIMER] = getRealTime();
+  }
+  inline void stop()
+  {
+    m_times[CPU_TIMER] = getCpuTime() - m_starts[CPU_TIMER];
+    m_times[REAL_TIMER] = getRealTime() - m_starts[REAL_TIMER];
+    #if EIGEN_VERSION_AT_LEAST(2,90,0)
+    m_bests = m_bests.cwiseMin(m_times);
+    m_worsts = m_worsts.cwiseMax(m_times);
+    #else
+    m_bests(0) = std::min(m_bests(0),m_times(0));
+    m_bests(1) = std::min(m_bests(1),m_times(1));
+    m_worsts(0) = std::max(m_worsts(0),m_times(0));
+    m_worsts(1) = std::max(m_worsts(1),m_times(1));
+    #endif
+    m_totals += m_times;
+  }
+
+  /** Return the elapsed time in seconds between the last start/stop pair
+    */
+  inline double value(int TIMER = CPU_TIMER) const
+  {
+    return m_times[TIMER];
+  }
+
+  /** Return the best elapsed time in seconds
+    */
+  inline double best(int TIMER = CPU_TIMER) const
+  {
+    return m_bests[TIMER];
+  }
+
+  /** Return the worst elapsed time in seconds
+    */
+  inline double worst(int TIMER = CPU_TIMER) const
+  {
+    return m_worsts[TIMER];
+  }
+
+  /** Return the total elapsed time in seconds.
+    */
+  inline double total(int TIMER = CPU_TIMER) const
+  {
+    return m_totals[TIMER];
+  }
+
+  inline double getCpuTime() const
+  {
+#ifdef _WIN32
+    LARGE_INTEGER query_ticks;
+    QueryPerformanceCounter(&query_ticks);
+    return query_ticks.QuadPart/m_frequency;
+#elif __APPLE__
+    return double(mach_absolute_time())*1e-9;
+#else
+    timespec ts;
+    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts);
+    return double(ts.tv_sec) + 1e-9 * double(ts.tv_nsec);
+#endif
+  }
+
+  inline double getRealTime() const
+  {
+#ifdef _WIN32
+    SYSTEMTIME st;
+    GetSystemTime(&st);
+    return (double)st.wSecond + 1.e-3 * (double)st.wMilliseconds;
+#elif __APPLE__
+    return double(mach_absolute_time())*1e-9;
+#else
+    timespec ts;
+    clock_gettime(CLOCK_REALTIME, &ts);
+    return double(ts.tv_sec) + 1e-9 * double(ts.tv_nsec);
+#endif
+  }
+
+protected:
+#if defined(_WIN32) || defined(__CYGWIN__)
+  double m_frequency;
+#endif
+  Vector2d m_starts;
+  Vector2d m_times;
+  Vector2d m_bests;
+  Vector2d m_worsts;
+  Vector2d m_totals;
+
+public:
+  EIGEN_MAKE_ALIGNED_OPERATOR_NEW
+};
+
+#define BENCH(TIMER,TRIES,REP,CODE) { \
+    TIMER.reset(); \
+    for(int uglyvarname1=0; uglyvarname1<TRIES; ++uglyvarname1){ \
+      TIMER.start(); \
+      for(int uglyvarname2=0; uglyvarname2<REP; ++uglyvarname2){ \
+        CODE; \
+      } \
+      TIMER.stop(); \
+    } \
+  }
+
+}
+
+// clean #defined tokens
+#ifdef EIGEN_BT_UNDEF_NOMINMAX
+# undef EIGEN_BT_UNDEF_NOMINMAX
+# undef NOMINMAX
+#endif
+
+#ifdef EIGEN_BT_UNDEF_WIN32_LEAN_AND_MEAN
+# undef EIGEN_BT_UNDEF_WIN32_LEAN_AND_MEAN
+# undef WIN32_LEAN_AND_MEAN
+#endif
+
+#endif // EIGEN_BENCH_TIMERR_H