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diff --git a/docs/proj/blas-lapack.xml b/docs/proj/blas-lapack.xml new file mode 100644 index 000000000..2b931fc49 --- /dev/null +++ b/docs/proj/blas-lapack.xml @@ -0,0 +1,509 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> +<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/proj/en/science/blas-lapack.xml,v 1.3 2007/12/27 19:35:25 bicatali Exp $ --> + +<guide link="/proj/en/science/blas-lapack.xml"> +<title>Using multiple versions of BLAS and LAPACK with Gentoo/Linux</title> + +<author title="Author"> + <mail link="bicatali@gentoo.org">Sébastien Fabbro</mail> +</author> +<author title="Author"> + <mail link="markusle@gentoo.org">Markus Dittrich</mail> +</author> +<author title="Editor"> + <mail link="nightmorph@gentoo.org">Joshua Saddler</mail> +</author> + +<abstract> +This guide explains the use of the different implementations of the BLAS +and LAPACK libraries that are available via Portage. +</abstract> + +<!-- The content of this document is licensed under the CC-BY-SA license --> +<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> +<license/> + +<version>1.0</version> +<date>2007-10-22</date> + +<chapter> +<title>Introduction</title> +<section> +<body> + +<p> +The Basic Linear Algebra Subroutines (BLAS) and Linear Algebra PACKage (LAPACK) +are well designed linear algebra software libraries developed by the +High Performance Computing (HPC) community. BLAS +implements dense matrix and vectors products, while LAPACK provides routines for +solving systems of linear equations. Both are widely used in +many scientific applications and it is, therefore, important to +have efficient implementations available. +</p> + +<p> +Originally written in FORTRAN 77, a number of additional language +wrappers have been developed for languages like C, C++, FORTRAN 95, and others. +The following legacy libraries are available via the reference ebuilds: +</p> + +<ul> + <li> + <uri link="http://netlib.org/blas">BLAS</uri>: FORTRAN 77 implementation of + BLAS + </li> + <li> + <uri link="http://netlib.org/blas">CBLAS</uri>: C implementation of BLAS + </li> + <li> + <uri link="http://netlib.org/lapack">LAPACK</uri>: FORTRAN 77 implementation + of LAPACK + </li> +</ul> + +<p> +In addition, Gentoo provides a number of optimized BLAS and LAPACK implementations +that will be described below. Different implementations are bundled together with +Gentoo's <c>eselect</c> system and the widely used <c>pkg-config</c> tool. +</p> + +<p> It is important to note that if you require, e.g., a well performing +BLAS implementation, simply emerging X over Y often is not enough. Rather, you will have +to carefully benchmark your applications since performance may depend +on many factors, +such as hardware or network. +If you are simply looking for a well performing and well tested +implementation, the reference ebuilds will likely be your best choice. +</p> + + +</body> +</section> +</chapter> + +<chapter> +<title>For Users</title> +<section> +<title>Installing</title> +<body> + +<p> +If best possible performance is not of paramount importance for you +and you simply +need BLAS and/or LAPACK, just emerge the virtual packages: +</p> + +<pre caption="Installing"> +# <i>emerge blas cblas lapack</i> +</pre> + +<p> +These will install the reference legacy packages from +<uri>http://netlib.org</uri>. They are well tested, easy to debug +implementations. They should satisfy most users; if they're all you need, you're +done reading. +</p> + +<p> +However, if: +</p> + +<ul> + <li>BLAS/LAPACK are critical for the speed of your applications</li> + <li>you absolutely need to build the fastest computer</li> + <li>you want to help Gentoo sci project to improve their packages</li> +</ul> + +<p> +... then read on, and be sure to file bugs both to Gentoo and upstream. +</p> + +<p> +There is a number of optimized implementations of these libraries in the Portage +tree: +</p> + +<ul> + <li> + <uri link="http://math-atlas.sourceforge.net">ATLAS</uri>: Automatically + Tuned Linear Algebra Software is an open-source package that empirically + tunes the library to the machine it is being compiled on. It provides BLAS + (FORTRAN 77 and C), and LAPACK implementations on various architectures. + </li> + <li> + <uri + link="http://www.tacc.utexas.edu/resources/software/software.php">GotoBLAS</uri>: + Goto BLAS provide open-source, free for academic use, hand-coded + machine language, processor optimized versions of the FORTRAN 77 BLAS + routines. Claims to be the fastest BLAS. + </li> + <li> + <uri link="http://developer.amd.com/acml.jsp">ACML</uri>: AMD Core Math + Library is a closed-source but free package containing BLAS (FORTRAN 77 + only) and LAPACK for x86 and amd64 architectures, but also other math tools + such as statistical libraries and FFTs. + </li> + <li> + <uri link="http://developer.intel.com/software/products/mkl/">MKL</uri>: + Intel® Math Kernel Library is a closed-source but free package for + non-commercial use containing BLAS (FORTRAN 77 and C), LAPACK optimized for + Intel® based architectures: x86, amd64 and ia64. + </li> +</ul> + +<p> +Usually performance gain is noticeable mainly with BLAS, since LAPACK routines +depend on BLAS kernels. +</p> + +</body> +</section> +<section> +<title>Compiling and linking with installed libraries</title> +<body> + +<p> +We took great care to make sure that each package provides consistent pkg-config files. +Hence, compiling and linking with BLAS/LAPACK should be simple and straightforward: +</p> + +<pre caption="Compiling and linking BLAS/LAPACK"> +# <i>pkg-config --libs blas</i> <comment>(To link with FORTRAN 77 BLAS library)</comment> +# <i>pkg-config --cflags cblas</i> <comment>(To compile against C BLAS library)</comment> +# <i>pkg-config --libs cblas</i> <comment>(To link with C BLAS library)</comment> +# <i>pkg-config --libs lapack</i> <comment>(To link with FORTRAN 77 LAPACK library)</comment> +</pre> + +<p> +<c>pkg-config</c> files are available for whichever implementation you select with <c>eselect</c>. +More information on using <c>pkg-config</c> can be obtained with <c>man pkg-config</c>. +</p> + +</body> +</section> +<section> +<title>Choosing libraries</title> +<body> + +<p> +You can easily switch BLAS, CBLAS and LAPACK implementations with +<c>eselect</c>. At this point, you probably have <c>eselect-blas</c>, +<c>eselect-cblas</c> and <c>eselect-lapack</c> installed. If you do not, +install them now! Using eselect, you can view which implementations of CBLAS +are available. +</p> + +<pre caption="Viewing available implementations"> +# <i>eselect cblas list</i> +Installed CBLAS for library directory lib64 +[1] atlas +[2] atlas-threads +[3] gsl +[4] mkl-threads * +[5] reference +</pre> + +<p> +The implementation marked with an asterisk (*) is the currently +selected implementation. To switch implementations, run: +</p> + +<pre caption="Switching to the ATLAS implementation of LAPACK"> +# <i>eselect lapack set atlas</i> +</pre> + +<p> +To learn more about the <c>eselect</c> tool, visit the +<uri link="http://www.gentoo.org/proj/en/eselect/user-guide.xml">eselect guide</uri> +</p> + +<p> +When selecting blas, cblas or lapack profiles try to avoid mixing +different implementations since we don't have any mechanism to enforce +reasonable profiles. However, here is a list of well performing +profile combinations that have been used successfully in the past: +</p> +<ul> + <li> Most CPUs: + <ul> + <li>blas,cblas: atlas (or atlas-threads with multi-processor)</li> + <li>lapack:atlas</li> + </ul> + </li> + <li> Most CPUs: + <ul> + <li>blas: goto </li> + <li>cblas,lapack: reference</li> + </ul> + </li> + <li> AMD based CPUs: + <ul> + <li>blas,lapack: acml-gfortran (or acml-gfortran-openmp with + multi-processors) </li> + <li>cblas: reference</li> + </ul> + </li> + <li> Intel based CPUs: + <ul> + <li>blas,cblas,lapack: mkl-threads</li> + </ul> + </li> +</ul> + +</body> +</section> + +<section> +<title>Choosing a compiler</title> +<body> + +<p> +Most of the libraries can compile with both the GNU compiler collection and the +Intel® compilers on the x86, amd64 and ia64 architectures. By default, you are +probably using <c>gcc</c>. You can also compile the <c>*-reference</c> packages +with <c>ifort</c> and <c>icc</c>. To do this, you need to define the F77 +environment variable and don't forget the FFLAGS. +</p> + +<pre caption="Using non-GCC compilers"> +# <i>F77=ifort FFLAGS="-O2 -mp" emerge blas-reference</i> +</pre> + +<p> +Depending on your hardware, a small performance gain can be noticed thanks to +vectorization. The <c>-mp</c> flag maintains floating-point precision, since by +default ifort is pretty aggressive on floating point arithmetic, and we are +actually compiling a math package. Try <c>man ifort</c> to see additional flags +to fit your hardware. +</p> + +<p> +Some of the implementations let you specify the Intel® C compiler as +well. Please beware that not all libraries compile with all +combinations. You should receive an error during the emerge in case you have +chosen an incompatible combination. +</p> + +<p> +As usual for Gentoo, there are many combinations of USE flags and +compilers with which you could compile a package. Unfortunately +switching compilers between BLAS and LAPACK might not be always +compatible. For example: +</p> + +<pre caption="Incompatible combinations"> +# <i>F77=ifort FFLAGS="-O2 -mp" USE="openmp" emerge =acml-3.6.0-r1</i> +# <i>eselect blas set acml-ifort-openmp</i> +# <i>F77=gfortran FFLAGS="-O2" emerge lapack-reference</i> +</pre> + +<p> +This will most likely break things or not even compile. +</p> + +<p> +Try to be consistent in your choice. Stay with the GCC most of the time will +avoid you some trouble, unless you want to use the MKL, in which case the Intel® +C and FORTRAN compilers make a good combination. +</p> + +</body> +</section> +<section> +<title>Documentation</title> +<body> + +<p> +If you need BLAS or LAPACK to develop your own programs, the documentation +becomes pretty handy. Setting the USE="doc" flag for the corresponding BLAS or +LAPACK package will install man pages and quick reference sheets from the +<c>app-doc/blas-docs</c> and <c>app-doc/lapack-docs</c> packages. They are +standard and valid for all implementations. For optimized packages, the +USE="doc" flags will usually install extra doc in PDF or HTML format. +</p> + +</body> +</section> +</chapter> + +<chapter> +<title>For Developers</title> +<section> +<title>Providing new implementations</title> +<body> + +<p> +The Portage tree contains many ebuilds that depend on the BLAS/CBLAS/LAPACK +libraries. As there is more than one possible implementation, the Gentoo +Scientific Project reorganized all the packages to provide <c>virtual/blas</c>, +<c>virtual/cblas</c>, and <c>virtual/lapack</c>. All ebuilds using BLAS should +depend on this virtual package, unless it is explicitly known to break with +different BLAS implementations. +</p> + +<p> +To work with Gentoo's configuration tools +<c>app-admin/eselect-{blas,cblas,lapack}</c>, and the virtual, every ebuild that +installs a BLAS implementation must fulfill following requirements: +</p> + +<ol> + <li> + The ebuild must install an eselect file for each profile it provides. The + libraries should link to the ones in <path>/usr/$(get_libdir)</path> + directories and the include files in <path>/usr/include</path>: + <ul> + <li> + <path>libblas.so[.0]</path> - Shared object for FORTRAN BLAS + applications + </li> + <li> + <path>libblas.a</path> - Static library for FORTRAN BLAS applications + </li> + <li> + <path>libcblas.so[.0]</path> - Shared object for C/C++ CBLAS applications + </li> + <li> + <path>libcblas.a</path> - Static library for C/C++ CBLAS applications + </li> + <li><path>cblas.h</path> - Include header for C/C++ applications</li> + <li> + <path>liblapack.so[.0]</path> - Shared object for FORTRAN LAPACK + applications + </li> + <li> + <path>liblapack.a</path> - Static library for FORTRAN LAPACK applications + </li> + </ul> + </li> + <li> + The ebuild must install a <path>blas.pc</path>, <path>cblas.pc</path> and/or + <path>lapack.pc</path> pkg-config file and therefore RDEPEND on + <c>dev-util/pkgconfig</c>. They should also be included in the eselect + files, and link to the <path>/usr/$(get_libdir)/pkgconfig</path> directory: + <ul> + <li><path>blas.pc</path> - BLAS pkg-config file</li> + <li><path>cblas.pc</path> - CBLAS pkg-config file</li> + <li><path>lapack.pc</path> - LAPACK pkg-config file</li> + </ul> + </li> + <li>Be included in the virtual package as a possible provider: + <ul> + <li><c>virtual/blas</c> - BLAS virtual package</li> + <li><c>virtual/cblas</c> - CBLAS virtual package</li> + <li><c>virtual/lapack</c> - LAPACK virtual package</li> + </ul> + </li> +</ol> + +<p> +The easiest way of understanding all this is probably getting inspiration from +one of the available packages. Currently the Portage tree provide the following +virtuals: +</p> + +<table> +<tr> + <th>Package name</th> + <th>virtual/blas</th> + <th>virtual/cblas</th> + <th>virtual/lapack</th> +</tr> +<tr> + <ti><c>sci-libs/acml</c></ti> + <ti>*</ti> + <ti></ti> + <ti>*</ti> +</tr> +<tr> + <ti><c>sci-libs/blas-atlas</c></ti> + <ti>*</ti> + <ti>*</ti> + <ti></ti> +</tr> +<tr> + <ti><c>sci-libs/blas-goto</c></ti> + <ti>*</ti> + <ti></ti> + <ti></ti> +</tr> +<tr> + <ti><c>sci-libs/blas-reference</c></ti> + <ti>*</ti> + <ti></ti> + <ti></ti> +</tr> +<tr> + <ti><c>sci-libs/cblas-reference</c></ti> + <ti></ti> + <ti>*</ti> + <ti></ti> +</tr> +<tr> + <ti><c>sci-libs/gsl</c></ti> + <ti></ti> + <ti>*</ti> + <ti></ti> +</tr> +<tr> + <ti><c>sci-libs/lapack-atlas</c></ti> + <ti></ti> + <ti></ti> + <ti>*</ti> +</tr> +<tr> + <ti><c>sci-libs/lapack-reference</c></ti> + <ti></ti> + <ti></ti> + <ti>*</ti> +</tr> +<tr> + <ti><c>sci-libs/mkl</c></ti> + <ti>*</ti> + <ti>*</ti> + <ti>*</ti> +</tr> +</table> + +</body> +</section> +<section> +<title>Packages with BLAS/LAPACK dependencies</title> +<body> + +<p> +Simply use <c>virtual/{blas,cblas,lapack}</c> as a [R]DEPEND. To build some +packages, you might need to use the pkg-config tool. If you are lucky, the +package uses autotools together with common BLAS and LAPACK M4 macros.In this +case, the configuration step becomes simple. For example: +</p> + +<pre caption="Sample package configuration"> +<keyword>econf</keyword> --with-blas="<var>$(pkg-config --libs blas)</var>" +</pre> + +<impo> +Don't forget to add <c>dev-util/pkgconfig</c> in DEPEND. +</impo> + +</body> +</section> +</chapter> + +<chapter> +<title>In the near future</title> +<section> +<body> + +<p> +We plan to include more standard BLAS, LAPACK libraries: BLAS 95, LAPACK 95, +Sparse BLAS, ScaLAPACK. If you feel inclined to write an ebuild for these, you +are more than welcomed to file it on our <uri +link="http://bugs.gentoo.org">Bugzilla</uri>. +</p> + +</body> +</section> +</chapter> +</guide> |