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ATLAS

Overview

The Automatically Tuned Linear Algebra Software (ATLAS) project is an ongoing research effort focusing on applying empirical techniques in order to provide portable performance. At present, it provides C and Fortran77 interfaces to a portably efficient BLAS implementation, as well as a few routines from LAPACK.

Setup

There is no setup needed for this software package.

Usage

ATLAS provides the following libraries:

liblapack.a
• a full LAPACK library containing a combination of functions optimized by the ATLAS project and functions from the LAPACK reference library.

libcblas.a
• a non-threaded ANSI C interface to BLAS.

libf77blas.a
• a non-threaded Fortran77 interface to BLAS.

libptcblas.a
• a threaded ANSI C interface to BLAS.

libptf77blas.a
• a threaded Fortran77 interface to BLAS.

libatlas.a
• the main ATLAS library providing low-level routines for all of the interface libraries.

Different compiler flags are necessary to link with different types of code that use BLAS and/or LAPACK.

For Fortran77 code calling non-threaded BLAS functions, these flags would be needed:

Fortran77 code calling threaded BLAS functions would need to replace the non-threaded library with the threaded:

For ANSI C code calling non-threaded BLAS functions, the following flags would be necessary:

ANSI C code calling threaded BLAS functions would need to replace the non-threaded library with the threaded:

When using the LAPACK library, both Fortran77 and ANSI C code use the same flags. For the non-threaded interface this would be:

For the threaded interface this would be:

Examples

For a Fortran77 file foo.f that uses BLAS functions and is compiled with pgf77 to create an executable foo the following command would be used:

For an ANSI C file quux.c that uses LAPACK functions and is compiled with gcc to create an executable quux the following command would be used:

Special Notice

Note that you may be an error when linking with ATLAS that looks like the following:

/usr/global/atlas/libf77blas.a(xerbla.o)(.text+0x18): In function `xerbla_':
: undefined reference to `s_wsfe'
/usr/global/atlas/libf77blas.a(xerbla.o)(.text+0x2f): In function `xerbla_':
: undefined reference to `do_fio'
/usr/global/atlas/libf77blas.a(xerbla.o)(.text+0x46): In function `xerbla_':
: undefined reference to `do_fio'
/usr/global/atlas/libf77blas.a(xerbla.o)(.text+0x50): In function `xerbla_':
: undefined reference to `e_wsfe'
collect2: ld returned 1 exit status

If you do, you need to compile your own copy of xerbla.f. Copy and paste the following into your working directory in a file named xerbla.f.

      SUBROUTINE XERBLA( SRNAME, INFO )
*
*  -- LAPACK auxiliary routine (preliminary version) --
*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
*     Courant Institute, Argonne National Lab, and Rice University
*     February 29, 1992
*
*     .. Scalar Arguments ..
      CHARACTER*6        SRNAME
      INTEGER            INFO
*     ..
*
*  Purpose
*  =======
*
*  XERBLA  is an error handler for the LAPACK routines.
*  It is called by an LAPACK routine if an input parameter has an
*  invalid value.  A message is printed and execution stops.
*
*  Installers may consider modifying the STOP statement in order to
*  call system-specific exception-handling facilities.
*
*  Arguments
*  =========
*
*  SRNAME  (input) CHARACTER*6
*          The name of the routine which called XERBLA.
*
*  INFO    (input) INTEGER
*          The position of the invalid parameter in the parameter list
*          of the calling routine.
*
*
      WRITE( *, FMT = 9999 )SRNAME, INFO
*
      STOP
*
 9999 FORMAT( ' ** On entry to ', A6, ' parameter number ', I2, ' had ',
     $      'an illegal value' )
*
*     End of XERBLA
*
      END

Compile to a .o file with

YOUR COMPILER HERE: -c xerbla.f

Example:

  pgf90 -c xerbla.f

Be sure to use the same compiler that you use to compile the rest of your application.

Then link in your own custom xerbla.o as follows:

YOUR COMPILER HERE YOUR_CODE.f90 xerbla.o ATLAS_LINK_COMMANDS_HERE -o output

Documentation

Documentation on ATLAS can be found in the ATLAS home page at:

Please send questions or suggestions about this web page to beatnic@aset.psu.edu

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