Finish the rest of r9698:

- Add a lengthy comment explaining why we don't get F90 data type
  alignments
- Remove config/f90_check.m4 and its entry in acinclude.m4

This commit was SVN r9707.

The following SVN revision numbers were found above:
  r9698 --> open-mpi/ompi@e57300da4c

acinclude.m4

@@ -10,6 +10,7 @@ dnl Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
 dnl                         University of Stuttgart.  All rights reserved.
 dnl Copyright (c) 2004-2005 The Regents of the University of California.
 dnl                         All rights reserved.
+dnl Copyright (c) 2006      Cisco Systems, Inc.
 dnl $COPYRIGHT$
 dnl 
 dnl Additional copyrights may follow
@@ -43,7 +44,6 @@ m4_include(config/f77_purge_unsupported_kind.m4)
 m4_include(config/f90_check.m4)
 m4_include(config/f90_check_type.m4)
 m4_include(config/f90_find_module_include_flag.m4)
-m4_include(config/f90_get_alignment.m4)
 m4_include(config/f90_get_precision.m4)
 m4_include(config/f90_get_range.m4)
 m4_include(config/f90_get_sizeof.m4)

config/f90_check.m4

@@ -26,7 +26,44 @@ dnl
 # - equal to expected size
 # - range (optional)
 # - precision (optional)
-#
+
+# Note that we do *not* check for the alignment here.  This is a long,
+# sordid tale.
+
+# We have been unable to devise a F90 test that will result in a
+# consistent answer.  Specifically, our prior tests have been similar
+# to the f77 test -- have a small chunk of f90 code compiled with the
+# C code to actually compute the offsets.  The f90 code was a
+# struct-like entity (a "type") with multiple members -- on a
+# character and the other of the target type.  The C code measured the
+# distance between them.  But even if you use the keyword to ensure
+# that the F90 compiler does not re-order this struct, you may still
+# get a different alignment answer than the F77 test (!).  This is
+# apparently because F90 allows compilers to align types differently
+# according to use (in common blocks, as standalone variables, and as
+# a member of a struct).  Hence, the alignment can be different
+# depending on how to measure (and use) it.  This was confirmed by
+# various members of the Fortran committee and several Fortran
+# compiler vendors.
+
+# We check the F77 alignment based on common block usage, but this is
+# only one of the available types for F90.  Hence, we may actually get
+# a different answer between f77 and f90 in the same compiler series
+# (and some compilers do!  E.g., g95 gives different answers even when
+# "g95" itself is used as both the f77 and f90 compiler).
+
+# So we gave up.
+
+# Additionally, this was really only a sanity check anyway, because
+# the way out F90 MPI layer is organized, there is no translation
+# between the data and datatypes performed -- we simply invoke the F77
+# layer from the F90 layer.  Hence, we make no distinction between
+# them, and therefore the OMPI DDT engine uses only the F77 sizes and
+# alignments.  So rather than display a warning to the user for a test
+# that was questionable at best, we just eliminated the F90 alignment
+# test, corresponding F77 comparison, and ensuring warning -- because
+# it really didn't mean anything anyway.
+
 # types to search is a comma-seperated list of values
 AC_DEFUN([OMPI_F90_CHECK], [
     ofc_fortran_type="$1"

config/f90_get_alignment.m4

@@ -1,91 +0,0 @@
-dnl -*- shell-script -*-
-dnl
-dnl Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
-dnl                         University Research and Technology
-dnl                         Corporation.  All rights reserved.
-dnl Copyright (c) 2004-2005 The University of Tennessee and The University
-dnl                         of Tennessee Research Foundation.  All rights
-dnl                         reserved.
-dnl Copyright (c) 2004-2005 High Performance Computing Center Stuttgart, 
-dnl                         University of Stuttgart.  All rights reserved.
-dnl Copyright (c) 2004-2005 The Regents of the University of California.
-dnl                         All rights reserved.
-dnl $COPYRIGHT$
-dnl 
-dnl Additional copyrights may follow
-dnl 
-dnl $HEADER$
-dnl
-
-# OMPI_F90_GET_ALIGNMENT(type, shell variable to set)
-# ---------------------------------------------------
-AC_DEFUN([OMPI_F90_GET_ALIGNMENT],[
-    AS_VAR_PUSHDEF([type_var], [ompi_cv_f90_alignment_$1])
-
-    AC_CACHE_CHECK([alignment of Fortran 90 $1], type_var,
-       [OMPI_F77_MAKE_C_FUNCTION([ompi_ac_align_fn], [align])
-        # Fortran module
-        cat > conftestf.f90 <<EOF
-program f90align
-  type TestAlign
-    character a
-    $1 :: x
-  end type
-  external align
-  type(TestAlign) :: a
-  call align(a%a, a%x)
-end program
-EOF
-
-        # C module
-        if test -f conftest.h; then
-            ompi_conftest_h="#include \"conftest.h\""
-        else
-            ompi_conftest_h=""
-        fi
-        cat > conftest.c <<EOF
-#include <stdio.h>
-#include <stdlib.h>
-$conftest
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-void $ompi_ac_align_fn(char *a, char *x);
-void $ompi_ac_align_fn(char *a, char *x)
-{   int diff;
-    FILE *f=fopen("conftestval", "w");
-    if (!f) exit(1);
-    diff = a - x;
-    fprintf(f, "%d\n", (diff >= 0) ? diff : -diff);
-    fclose(f);
-}
-#ifdef __cplusplus
-}
-#endif
-EOF
-
-        OMPI_LOG_COMMAND([$CC $CFLAGS -I. -c conftest.c],
-            [OMPI_LOG_COMMAND([$FC $FCFLAGS $FCFLAGS_f90 conftestf.f90 conftest.o -o conftest $LDFLAGS $LIBS],
-                [happy="yes"], [happy="no"])], [happy="no"])
-
-        if test "$happy" = "no" ; then
-             OMPI_LOG_MSG([here is the fortran 90 program:], 1)
-             OMPI_LOG_FILE([conftestf.f90])
-             AC_MSG_WARN([Could not determine alignment of $1])
-             AC_MSG_WARN([See config.log for details])
-             AC_MSG_ERROR([Cannot continue])
-        fi
-
-        AS_IF([test "$cross_compiling" = "yes"],
-            [AC_MSG_ERROR([Can not determine alignment of $1 when cross-compiling])],
-            [OMPI_LOG_COMMAND([./conftest],
-                [AS_VAR_SET(type_var, [`cat conftestval`])],
-                [AC_MSG_ERROR([Could not determine alignment of $1])])])
-
-        unset happy ompi_conf
-        rm -f conftest*])
-
-    $2=AS_VAR_GET([type_var])
-    AS_VAR_POPDEF([type_var])dnl
-])