Getting libaec
==============

The source code of libaec is hosted at DKRZ GitLab.

## Source code and binary releases

The latest releases of libaec can be downloaded at the following
location:

  https://gitlab.dkrz.de/k202009/libaec/tags

## Developer snapshot

  git clone https://gitlab.dkrz.de/k202009/libaec.git

This version of libaec has been changed by The HDF Group to work within the framework of hdf5.

1. Obtaining the HDF version of libaec

   The latest supported public release of HDF libaec is available from The
   HDF Group's (THG) FTP server:
       ftp://ftp.hdfgroup.org/lib-external/libaec/1.0.4

Installation
============

## General considerations

Libaec achieves the best performance on 64 bit systems. The library
will work correctly on 32 bit systems but encoding and decoding
performance will be much lower.

## Installation from source code release with configure

The most common installation procedure on Unix-like systems looks as
follows:

Unpack the tar archive and change into the unpacked directory.

  mkdir build
  cd build
  ../configure
  make check install

## Installation from source code release with CMake

As an alternative, you can use CMake to install libaec.

   1.   We suggest you obtain the latest CMake for windows from the Kitware
        web site. This product requires a minimum CMake version 3.2.2.

   2.   We use the file cacheinit.cmake in the
        config/cmake source folder for our testing. This file enables all of the
        basic options and we turn specific options on or off for testing
        using the following command line within the build directory:

        cmake -C <sourcepath>/config/cmake/cacheinit.cmake -G "<generator>"  [-D<options>]  <sourcepath>

        Where <generator> is
            * MinGW Makefiles
            * NMake Makefiles
            * Unix Makefiles
            * Visual Studio 12 2013
            * Visual Studio 12 2013 Win64
            * Visual Studio 11 2012
            * Visual Studio 11 2012 Win64
            * Visual Studio 14 2015
            * Visual Studio 14 2015 Win64

        <cacheinit.cmake> is:
                # This is the CMakeCache file used by HDF Group for daily tests.
                ########################
                # EXTERNAL cache entries
                ########################
                set (BUILD_SHARED_LIBS ON CACHE BOOL "Build Shared Libraries" FORCE)
                set (CMAKE_INSTALL_FRAMEWORK_PREFIX "Library/Frameworks" CACHE STRING "Frameworks installation directory" FORCE)
                set (LIBAEC_PACKAGE_EXT "" CACHE STRING "Name of package extension" FORCE)
                set (BUILD_TESTING ON CACHE BOOL "Build LIBAEC Unit Testing" FORCE)


Intel compiler settings
=======================

The Intel compiler can improve performance by vectorizing certain
parts of the code on x86 architectures. Assuming your CPU supports
AVX2, the following options will increase encoding speed.

  ../configure CC=icc
  make CFLAGS="-O3 -xCORE-AVX2" bench

On a 3.4 GHz E3-1240 v3 we see more than 400 MiB/s for encoding
typical data.

Using other SIMD instruction sets on older CPUs may also help.

User Support
=======================
   Report problems to help@hdfgroup.org.