HISTORY

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High Performance Conjugate Gradient Benchmark (HPCG)
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:Author: Jack Dongarra and Michael Heroux and Piotr Luszczek
:Revision: 3.0
:Date: November 11, 2015

===============
History of HPCG
===============

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Version 3.0
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* Added problem generation as a timed portion of the benchmark.  This time is now
  added to any time spent optimizing data structures and counted as overhead when
  computing the official GFLOP/s rating.  The total overhead time is divided by 500
  to amortize its cost over 500 iterations.

* Added memory usage counting and reporting.

* Added memory bandwidth measurement and reporting.

* Added a "Quick Path" option to make obtaining results on production systems easier.
  With this option, obtaining a rating will take only a few minutes.  This option also
  makes profiling and debugging easier.  The Quick Path option is invoked by setting the
  run time to zero, either in hpcg.dat or by using the --rt=0 option.

* Added a command line option (--rt=) to specify the run time.

* Made a few small changes to support easier builds on MS Windows.

* Changed the way the residual variance is computed to make sure it is zero if all
  residual values are identical.

* Changed the order of array allocation in the reference code in order to improve
  performance.

* Set the minimum iteration count for the optimized run to be the same as what is
  used in the reference run.

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Version 2.4
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* Fixed (again) the FLOP count for DDOT and WAXPBY.  We forgot that the
  preamble is called many times.

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Version 2.3
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* Fixed the FLOP count for DDOT and WAXPBY.  The operations in the preamble were
  not being accounted for.

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Version 2.2
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* Reduced the penalty for optimization overhead by a factor of 10 (amortized over 10
  sets of 50 reference iterations.
* Fixed a bug that did not account for increased iterations that can occur with
  multicoloring reorderings.
* Fixed numerous other small bugs reported by HPCG users.

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Version 2.1
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* Fixed a small but important bug in ComputeProlongation_ref.cpp (- sign should be + sign).

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Version 2.0
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* Added support for a synthetic multigrid V cycle.  Parameters include
  the number of levels in the the grid hierarchy, number of pre and
  post smoother steps.
* Refactored data classes to support needs for recursion in V cycle.
* Made simple modifications to make compilation on MS Windows easier.
  This includes changing the format of output files to remove colons.

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Version 1.1
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* Added a simple code for users remove in order to indicate whether
  optimization was done for dot-product, SPMV, SYMGS, or WAXPBY.

* Fixed a problem with computing the variance of results from multiple runs.

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Version 1.0
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* Changed the diagonal entry from 27 to 26 to influence convergence rate.

* Changed license file (COPYRIGHT) from 4-clause BSD (original BSD) to 3-clause
  BSD (modified BSD)

* Added a line to the input file (hpcg.dat) that allows to specify time to run
  the benchmark.

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Version 0.5
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* Improved the formula used for scaling of departure of symmetry

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Version 0.4
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* Fixed bugs in integer computations where intermediate 32-bit
  integer computations resulted in values that exceeded the
  32-bit range and gave incorrect results.

* Fixed the computation of the number of CG set runs to take
  into account varying timing results across MPI processes.

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Version 0.3
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* Given out to friendly testers.

* Includes Doxygen output.

* Numerous small changes.

* Substantially improved output.

* Tested on large systems.

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Version 0.2
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* Given out to "friends".

* Numerous small changes.


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Version 0.1
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* Added local symmetric Gauss-Seidel preconditioning.

* Changed global geometry to be true 3D.  Previously was a beam (subdomains
  were stacked only in the z dimension).

* Introduced three global/local index modes: 32/32, 64/32, 64/64 to handle all
  problem sizes.

* Changed execution strategy to perform multiple runs with just a few
  iterations per run.

* Added infrastructure and rules for user adaptation of kernels for performance
  optimization.

* Added benchmark modification and reporting rules.

* Changed directory and file layout to mimic HPL layouts where appropriate.

================
History of HPCCG
================

--------------------------
NAME CHANGE: HPCCG to HPCG
--------------------------

* The name was changed from HPCCG to HPCG without any code changes.

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Version 1.0
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* Released as part of Mantevo Suite 1.0, December 2012.

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Version 0.5
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* Added timing for Allreduce calls in MPI mode, printing min/max/avg times.

* Set the solver tolerance to zero to make all solves take ``max_iter``
  iterations.

* Changed accumulator to a local variable for ``ddot``.  It seems to help
  dual-core performance.

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Version 0.4
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* Made total_nnz a "long long" so that MFLOP numbers were valid
  when the nonzero count is  more than 2^31.

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Version 0.3
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* Fixed a performance bug in ``make_local_matrix.cpp`` that was very noticeable
  when the fraction of off-processor grid points was large.

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Version 0.2
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* Fixed bugs related to turning MPI compilation off.

* Added more text to README to improve understanding.

* Added new ``Makfile.x86linux.gcc`` for non-opteron systems.

* Made ``MPI_Wtime`` the default timer when in MPI mode.

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Version 0.1
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HPCCG (Original version) was written as a teaching code for illustrating the
anatomy of a distributed memory parallel sparse iterative solver for new
research students and junior staff members.  March 2000.