Hi Hristo, Stefan
This is more Fortran than MPI or OpenMPI, but anyway ...
Thank you for clarifying the point on F2003 automatic
allocation/reallocation.
What was illegal in the 20th century
became legal in the new millenium,
at least when it comes to Fortran.
I confess I have to read each sentence in Metcalf's book
several times to try to understand the nifty new Matlabish
syntax and the semantics of 21st century Fortran ..., and alas,
I am still interpreting it wrong.
The only consolation is that even the Gnu compiler seems to be
in my boat! :)
I don't know how much is gained by concatenating arrays that don't
exist yet (or objects that have an allocatable but not yet allocated
array as their single component), and how much memory management
contortion and fragmentation this may perhaps entail,
but there may be some advantage to it.
Stefan reports that if he allocates explicitly the arrays,
"everything is fine".
So, why not? :)
At least for portability, as it would allow compilation with
compilers that are not yet fully F2003 compliant,
older F90 compilers, etc.
I may be wrong, but my recollection from a situation that
happened here years ago,
and which may bear some similarity to the problem reported by Stefan,
is that Intel ifort would assign one memory word to
allocatable arrays, even before they were actually allocated,
so that you could have a cavalier approach and refer to those
arrays in the RHS of equations at any time,
whereas Gnu gfortran required explicit memory allocation before
those arrays were used.
At that point the ifort behavior seemed to be a lenient extension,
whereas the gfortran behavior a more strict compliance to the standard
(which was still F90 or F95 then, IIRR).
However, this may have changed on more recent versions of those
compilers, and also to conform with more recent versions of the Fortran
standard.
Thank you,
Gus Correa
On 01/14/2013 04:48 AM, Iliev, Hristo wrote:
Hi, Gus,
Automatic allocation (an reallocation) on assignment is among the nifty
features of Fortran 2003. In this case "conc" is automatically allocated so
to match the shape of its initialiser array "[ xx, yy ]". Note that "xx" and
"yy" are not allocatable though their derived type has an allocatable
element.
Kind regards,
Hristo Iliev
-----Original Message-----
From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org]
On Behalf Of Gus Correa
Sent: Friday, January 11, 2013 7:19 PM
To: Open MPI Users
Subject: Re: [OMPI users] Initializing OMPI with invoking the array
constructor on Fortran derived types causes the executable to crash
Hi Stefan
Don't you need to allocate xx, yy and conc, before you use them?
In the short program below, they are declared as allocatable, but not
actually
allocated.
I hope this helps,
Gus Correa
On 01/11/2013 09:58 AM, Stefan Mauerberger wrote:
Dear Paul!
Thanks for your reply. This problem seems to get complicated.
Unfortunately, I can not reproduce what you are describing. I tried
with some GCCs as 4.7.1, 4.7.2 and 4.8.0 (20121008). As you suggested,
replacing the MPI_Init and MPI_Finalize calls with WRITE(*,*) "foooo"
and commenting out use mpi, everything is just fine. No segfault no
core dump, just the result as I expect it (I put a write(*,*)
size(conc) in, which must print 2). I simply compiled with a bare
mpif90 ... and executed typing mpirun -np 1 ./a.out .
I also tried on three different architectures - all 64-bit - and, as
soon as MPI_Init is invoked, the program gets core dumped.
I also tried with IBM's MPI implementation just with the difference
using include 'mpif.h' instead of use mpi. Everything is fine and the
result is as in serial runs.
Well, it's not surprising that 4.4.x has its problems. Using modern
Fortran as F03, GCC in a version younger than 4.7.x is just mandatory.
Cheers,
Stefan
On Fri, 2013-01-11 at 14:26 +0100, Paul Kapinos wrote:
This is hardly an Open MPI issue:
switch the calls to MPI_Init, MPI_Finalize against
WRITE(*,*) "foooo"
comment aut 'USE mpi' .... an see your error (SIGSEGV) again, now
without any MPI part in the program.
So my suspiction is this is an bug in your GCC version. Especially
because there is no SIGSEGV using 4.7.2 GCC (whereby it crasehs using
4.4.6)
==> Update your compilers!
On 01/11/13 14:01, Stefan Mauerberger wrote:
Hi There!
First of all, this is my first post here. In case I am doing
something inappropriate pleas be soft with me. On top of that I am
not quite sure whether that issue is related to Open MPI or GCC.
Regarding my problem: Well, it is a little bulky, see below. I could
figure out that the actual crash is caused by invoking Fortran's
array constructor [ xx, yy ] on derived-data-types xx and yy. The
one key factor is that those types have allocatable member variables.
Well, that fact points to blame gfortran for that. However, the
crash does not occur if MPI_Iinit is not called in before. Compiled
as a serial program everything works perfectly fine. I am pretty
sure, the lines I wrote are valid F2003 code.
Here is a minimal working example:
PROGRAM main
USE mpi
IMPLICIT NONE
INTEGER :: ierr
TYPE :: test_typ
REAL, ALLOCATABLE :: a(:)
END TYPE
TYPE(test_typ) :: xx, yy
TYPE(test_typ), ALLOCATABLE :: conc(:)
CALL mpi_init( ierr )
conc = [ xx, yy ]
CALL mpi_finalize( ierr )
END PROGRAM main
Just compile with mpif90 ... and execute leads to:
*** glibc detected *** ./a.out: free(): invalid pointer:
0x00007fefd2a147f8 *** ======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7eb96)[0x7fefd26dab96]
./a.out[0x400fdb]
./a.out(main+0x34)[0x401132]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7fefd267d
76d]
./a.out[0x400ad9]
With commenting out 'CALL MPI_Init' and 'MPI_Finalize' everything
seems to be fine.
What do you think: Is this a OMPI or a GCC related bug?
Cheers,
Stefan
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--
Hristo Iliev, Ph.D. -- High Performance Computing
RWTH Aachen University, Center for Computing and Communication
Rechen- und Kommunikationszentrum der RWTH Aachen
Seffenter Weg 23, D 52074 Aachen (Germany)
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