Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 85 insertions, 0 deletions

diff --git a/src/boost/libs/fusion/example/performance/measure.hpp b/src/boost/libs/fusion/example/performance/measure.hpp
new file mode 100644
index 00000000..72cd71ba
--- /dev/null
+++ b/src/boost/libs/fusion/example/performance/measure.hpp
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+// Copyright David Abrahams, Matthias Troyer, Michael Gauckler
+// 2005. Distributed under the Boost Software License, Version
+// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#if !defined(LIVE_CODE_TYPE)
+# define LIVE_CODE_TYPE int
+#endif
+
+#include <boost/timer.hpp>
+
+namespace test
+{
+  // This value is required to ensure that a smart compiler's dead
+  // code elimination doesn't optimize away anything we're testing.
+  // We'll use it to compute the return code of the executable to make
+  // sure it's needed.
+  LIVE_CODE_TYPE live_code;
+
+  // Call objects of the given Accumulator type repeatedly with x as
+  // an argument.
+  template <class Accumulator, class Arg>
+  void hammer(Arg const& x, long const repeats)
+  {
+      // Strategy: because the sum in an accumulator after each call
+      // depends on the previous value of the sum, the CPU's pipeline
+      // might be stalled while waiting for the previous addition to
+      // complete.  Therefore, we allocate an array of accumulators,
+      // and update them in sequence, so that there's no dependency
+      // between adjacent addition operations.
+      //
+      // Additionally, if there were only one accumulator, the
+      // compiler or CPU might decide to update the value in a
+      // register rather that writing it back to memory.  we want each
+      // operation to at least update the L1 cache.  *** Note: This
+      // concern is specific to the particular application at which
+      // we're targeting the test. ***
+
+      // This has to be at least as large as the number of
+      // simultaneous accumulations that can be executing in the
+      // compiler pipeline.  A safe number here is larger than the
+      // machine's maximum pipeline depth. If you want to test the L2
+      // or L3 cache, or main memory, you can increase the size of
+      // this array.  1024 is an upper limit on the pipeline depth of
+      // current vector machines.
+      const std::size_t number_of_accumulators = 1024;
+      live_code = 0; // reset to zero
+
+      Accumulator a[number_of_accumulators];
+      
+      for (long iteration = 0; iteration < repeats; ++iteration)
+      {
+          for (Accumulator* ap = a;  ap < a + number_of_accumulators; ++ap)
+          {
+              (*ap)(x);
+          }
+      }
+
+      // Accumulate all the partial sums to avoid dead code
+      // elimination.
+      for (Accumulator* ap = a;  ap < a + number_of_accumulators; ++ap)
+      {
+          live_code += ap->sum;
+      }
+  }
+
+  // Measure the time required to hammer accumulators of the given
+  // type with the argument x.
+  template <class Accumulator, class T>
+  double measure(T const& x, long const repeats)
+  {
+      // Hammer accumulators a couple of times to ensure the
+      // instruction cache is full of our test code, and that we don't
+      // measure the cost of a page fault for accessing the data page
+      // containing the memory where the accumulators will be
+      // allocated
+      hammer<Accumulator>(x, repeats);
+      hammer<Accumulator>(x, repeats);
+
+      // Now start a timer
+      boost::timer time;
+      hammer<Accumulator>(x, repeats);  // This time, we'll measure
+      return time.elapsed() / repeats;  // return the time of one iteration
+  }
+}