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+dnl @synopsis ACX_LAPACK([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
+dnl
+dnl This macro looks for a library that implements the LAPACK
+dnl linear-algebra interface (see http://www.netlib.org/lapack/).
+dnl On success, it sets the LAPACK_LIBS output variable to
+dnl hold the requisite library linkages.
+dnl
+dnl To link with LAPACK, you should link with:
+dnl
+dnl     $LAPACK_LIBS $BLAS_LIBS $LIBS $FLIBS
+dnl
+dnl in that order.  BLAS_LIBS is the output variable of the ACX_BLAS
+dnl macro, called automatically.  FLIBS is the output variable of the
+dnl AC_F77_LIBRARY_LDFLAGS macro (called if necessary by ACX_BLAS),
+dnl and is sometimes necessary in order to link with F77 libraries.
+dnl Users will also need to use AC_F77_DUMMY_MAIN (see the autoconf
+dnl manual), for the same reason.
+dnl
+dnl The user may also use --with-lapack=<lib> in order to use some
+dnl specific LAPACK library <lib>.  In order to link successfully,
+dnl however, be aware that you will probably need to use the same
+dnl Fortran compiler (which can be set via the F77 env. var.) as
+dnl was used to compile the LAPACK and BLAS libraries.
+dnl
+dnl ACTION-IF-FOUND is a list of shell commands to run if a LAPACK
+dnl library is found, and ACTION-IF-NOT-FOUND is a list of commands
+dnl to run it if it is not found.  If ACTION-IF-FOUND is not specified,
+dnl the default action will define HAVE_LAPACK.
+dnl
+dnl @version $Id: acx_lapack.m4,v 1.3 2002/03/12 09:12:44 simons Exp $
+dnl @author Steven G. Johnson <stevenj@alum.mit.edu>
+
+AC_DEFUN([ACX_LAPACK], [
+AC_REQUIRE([ACX_BLAS])
+acx_lapack_ok=no
+
+AC_ARG_WITH(lapack,
+        [AC_HELP_STRING([--with-lapack=<lib>], [use LAPACK library <lib>])])
+case $with_lapack in
+        yes | "") ;;
+        no) acx_lapack_ok=disable ;;
+        -* | */* | *.a | *.so | *.so.* | *.o) LAPACK_LIBS="$with_lapack" ;;
+        *) LAPACK_LIBS="-l$with_lapack" ;;
+esac
+
+# Get fortran linker name of LAPACK function to check for.
+AC_F77_FUNC(cheev)
+
+# We cannot use LAPACK if BLAS is not found
+if test "x$acx_blas_ok" != xyes; then
+        acx_lapack_ok=noblas
+fi
+
+# First, check LAPACK_LIBS environment variable
+if test "x$LAPACK_LIBS" != x; then
+        save_LIBS="$LIBS"; LIBS="$LAPACK_LIBS $BLAS_LIBS $LIBS $FLIBS"
+        AC_MSG_CHECKING([for $cheev in $LAPACK_LIBS])
+        AC_TRY_LINK_FUNC($cheev, [acx_lapack_ok=yes], [LAPACK_LIBS=""])
+        AC_MSG_RESULT($acx_lapack_ok)
+        LIBS="$save_LIBS"
+        if test acx_lapack_ok = no; then
+                LAPACK_LIBS=""
+        fi
+fi
+
+# LAPACK linked to by default?  (is sometimes included in BLAS lib)
+if test $acx_lapack_ok = no; then
+        save_LIBS="$LIBS"; LIBS="$LIBS $BLAS_LIBS $FLIBS"
+        AC_CHECK_FUNC($cheev, [acx_lapack_ok=yes])
+        LIBS="$save_LIBS"
+fi
+
+# Generic LAPACK library?
+for lapack in lapack lapack_rs6k; do
+        if test $acx_lapack_ok = no; then
+                save_LIBS="$LIBS"; LIBS="$BLAS_LIBS $LIBS"
+                AC_CHECK_LIB($lapack, $cheev,
+                    [acx_lapack_ok=yes; LAPACK_LIBS="-l$lapack"], [], [$FLIBS])
+                LIBS="$save_LIBS"
+        fi
+done
+
+AC_SUBST(LAPACK_LIBS)
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test x"$acx_lapack_ok" = xyes; then
+        ifelse([$1],,AC_DEFINE(HAVE_LAPACK,1,[Define if you have LAPACK library.]),[$1])
+        :
+else
+        acx_lapack_ok=no
+        $2
+fi
+])dnl ACX_LAPACK