Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and other questions

2016-08-21 Thread Ben Menadue 
Hi,

 

In Fortran, using uninitialised variables is undefined behaviour. In this case, 
it’s being initialised to zero (either by the compiler or by virtue of being in 
untouched memory), and so equivalent to MPI_COMM_WORLD in OpenMPI. Other MPI 
libraries don’t have MPI_COMM_WORLD .eq. 0 and so the same program would fail. 
Similarly, if the same memory has previously been stored to (and so non-zero) 
and the compiler doesn’t zero-initialise the variable (most won’t unless you 
explicitly ask for it), it will fail with OpenMPI.

 

Just keep in mind that the same is true for *all* variables in Fortran; even 
integers and reals have undefined value until they’re first stored to. This can 
be quite annoying as specifying the initial value when declaring them also 
gives them the SAVE attribute…

 

Cheers,

Ben

 

From: users [mailto:users-boun...@lists.open-mpi.org] On Behalf Of Matt Thompson
Sent: Sunday, 21 August 2016 3:07 AM
To: Open MPI Users 
Subject: Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and 
other questions

 

 

On Fri, Aug 19, 2016 at 8:54 PM, Jeff Squyres (jsquyres) mailto:jsquy...@cisco.com> > wrote:

On Aug 19, 2016, at 6:32 PM, Matt Thompson mailto:fort...@gmail.com> > wrote:

> > that the comm == MPI_COMM_WORLD evaluates to .TRUE.? I discovered that once 
> > when I was printing some stuff.
>
> That might well be a coincidence.  type(MPI_Comm) is not a boolean type, so 
> I'm not sure how you compared it to .true.
>
> Well, I made a program like:
>
> (208) $ cat test2.F90
> program whoami
>use mpi_f08
>implicit none
>type(MPI_Comm) :: comm
>if (comm == MPI_COMM_WORLD) write (*,*) "I am MPI_COMM_WORLD"
>if (comm == MPI_COMM_NULL) write (*,*) "I am MPI_COMM_NULL"
> end program whoami
> (209) $ mpifort test2.F90
> (210) $ mpirun -np 4 ./a.out
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>
> I think if you print comm, you get 0 and MPI_COMM_WORLD=0 and MPI_COMM_NULL=2 
> so...I guess I'm surprised. I'd have thought MPI_Comm would have been 
> undefined until defined.

I don't know the rules here for what happens in Fortran when comparing an 
uninitialized derived type.  The results could be undefined...?


> Instead you can write a program like this:
>
> (226) $ cat helloWorld.mpi3.F90
> program hello_world
>
>use mpi_f08
>
>implicit none
>
>type(MPI_Comm) :: comm
>integer :: myid, npes, ierror
>integer :: name_length
>
>character(len=MPI_MAX_PROCESSOR_NAME) :: processor_name
>
>call mpi_init(ierror)
>
>call MPI_Comm_Rank(comm,myid,ierror)
>write (*,*) 'ierror: ', ierror
>call MPI_Comm_Size(comm,npes,ierror)
>call MPI_Get_Processor_Name(processor_name,name_length,ierror)
>
>write (*,'(A,X,I4,X,A,X,I4,X,A,X,A)') "Process", myid, "of", npes, "is 
> on", trim(processor_name)
>
>call MPI_Finalize(ierror)
>
> end program hello_world
> (227) $ mpifort helloWorld.mpi3.F90
> (228) $ mpirun -np 4 ./a.out
>  ierror:0
>  ierror:0
>  ierror:0
>  ierror:0
> Process2 of4 is on compy
> Process1 of4 is on compy
> Process3 of4 is on compy

> Process0 of4 is on copy

That does seem to be odd output.  What is the hostname on your machine?  

 

Oh well, I (badly) munged the hostname on the computer I ran on because it had 
the IP address within. I figured better safe than sorry and not broadcast that 
out there. :)

 

FWIW, I changed your write statement to:

print *, "Process", myid, "of", npes, "is on", trim(processor_name)

and after I added a "comm = MPI_COMM_WORLD" before the call to MPI_COMM_RANK, 
the output prints properly for me (i.e., I see my hostname).

> This seems odd to me. I haven't passed in MPI_COMM_WORLD as the communicator 
> to MPI_Comm_Rank, and yet, it worked and the error code was 0 (which I'd take 
> as success). Even if you couldn't detect this at compile time, I'm surprised 
> it doesn't trigger a run-time error.  Is this the correct behavior according 
> to the Standard?

I think you're passing an undefined value, so the results will be undefined.

It's quite possible that the comm%mpi_val inside the comm is (randomly?) 
assigned to 0, which is the same value as mpif.f's MPI_COMM_WORLD, and 
therefore your comm is effectively the same as mpi_f08's MPI_COMM_WORLD -- 
which is why MPI_COMM_RANK and MPI_COMM_SIZE worked for you.

Indeed, when I run your program, I get:

-
$ ./foo
[savbu-usnic-a:31774] *** An error occurred in MPI_Comm_rank
[savbu-usnic-a:31774] *** reported by process [756088833,0]
[savbu-usnic-a:31774] *** on communicator MPI_COMM_WORLD
[savbu-usnic-a:31774] *** MPI_ERR_COMM: invalid communicator
[savbu-usnic-a:31774] *** MPI_ERRORS_ARE_FATAL (processes in this communicator 
will now abort,
[savbu-usnic-a:31774] ***and potentially your MPI job)
-

I.e., MPI_COMM_RANK is aborting because the communicator being passed in is 
invali

Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and other questions

2016-08-21 Thread Jeff Hammond 
On Sunday, August 21, 2016, Ben Menadue  wrote:

> Hi,
>
>
>
> In Fortran, using uninitialised variables is undefined behaviour. In this
> case, it’s being initialised to zero (either by the compiler or by virtue
> of being in untouched memory), and so equivalent to MPI_COMM_WORLD in
> OpenMPI. Other MPI libraries don’t have MPI_COMM_WORLD .eq. 0 and so the
> same program would fail. Similarly, if the same memory has previously been
> stored to (and so non-zero) and the compiler doesn’t zero-initialise the
> variable (most won’t unless you explicitly ask for it), it will fail with
> OpenMPI.
>
>
Such false successes are a (the?) reason why MPI libraries should not
define valid handles to default initializers, whether they
be standardized or implementation-specific...

Jeff

>
>
> Just keep in mind that the same is true for *all* variables in Fortran;
> even integers and reals have undefined value until they’re first stored to.
> This can be quite annoying as specifying the initial value when declaring
> them also gives them the SAVE attribute…
>
>
>
> Cheers,
>
> Ben
>
>
>
> *From:* users [mailto:users-boun...@lists.open-mpi.org
> ] *On
> Behalf Of *Matt Thompson
> *Sent:* Sunday, 21 August 2016 3:07 AM
> *To:* Open MPI Users  >
> *Subject:* Re: [OMPI users] mpi_f08 Question: set comm on declaration
> error, and other questions
>
>
>
>
>
> On Fri, Aug 19, 2016 at 8:54 PM, Jeff Squyres (jsquyres) <
> jsquy...@cisco.com >
> wrote:
>
> On Aug 19, 2016, at 6:32 PM, Matt Thompson  > wrote:
>
> > > that the comm == MPI_COMM_WORLD evaluates to .TRUE.? I discovered that
> once when I was printing some stuff.
> >
> > That might well be a coincidence.  type(MPI_Comm) is not a boolean type,
> so I'm not sure how you compared it to .true.
> >
> > Well, I made a program like:
> >
> > (208) $ cat test2.F90
> > program whoami
> >use mpi_f08
> >implicit none
> >type(MPI_Comm) :: comm
> >if (comm == MPI_COMM_WORLD) write (*,*) "I am MPI_COMM_WORLD"
> >if (comm == MPI_COMM_NULL) write (*,*) "I am MPI_COMM_NULL"
> > end program whoami
> > (209) $ mpifort test2.F90
> > (210) $ mpirun -np 4 ./a.out
> >  I am MPI_COMM_WORLD
> >  I am MPI_COMM_WORLD
> >  I am MPI_COMM_WORLD
> >  I am MPI_COMM_WORLD
> >
> > I think if you print comm, you get 0 and MPI_COMM_WORLD=0 and
> MPI_COMM_NULL=2 so...I guess I'm surprised. I'd have thought MPI_Comm would
> have been undefined until defined.
>
> I don't know the rules here for what happens in Fortran when comparing an
> uninitialized derived type.  The results could be undefined...?
>
>
> > Instead you can write a program like this:
> >
> > (226) $ cat helloWorld.mpi3.F90
> > program hello_world
> >
> >use mpi_f08
> >
> >implicit none
> >
> >type(MPI_Comm) :: comm
> >integer :: myid, npes, ierror
> >integer :: name_length
> >
> >character(len=MPI_MAX_PROCESSOR_NAME) :: processor_name
> >
> >call mpi_init(ierror)
> >
> >call MPI_Comm_Rank(comm,myid,ierror)
> >write (*,*) 'ierror: ', ierror
> >call MPI_Comm_Size(comm,npes,ierror)
> >call MPI_Get_Processor_Name(processor_name,name_length,ierror)
> >
> >write (*,'(A,X,I4,X,A,X,I4,X,A,X,A)') "Process", myid, "of", npes,
> "is on", trim(processor_name)
> >
> >call MPI_Finalize(ierror)
> >
> > end program hello_world
> > (227) $ mpifort helloWorld.mpi3.F90
> > (228) $ mpirun -np 4 ./a.out
> >  ierror:0
> >  ierror:0
> >  ierror:0
> >  ierror:0
> > Process2 of4 is on compy
> > Process1 of4 is on compy
> > Process3 of4 is on compy
>
> > Process0 of4 is on copy
>
> That does seem to be odd output.  What is the hostname on your machine?
>
>
>
> Oh well, I (badly) munged the hostname on the computer I ran on because it
> had the IP address within. I figured better safe than sorry and not
> broadcast that out there. :)
>
>
>
> FWIW, I changed your write statement to:
>
> print *, "Process", myid, "of", npes, "is on", trim(processor_name)
>
> and after I added a "comm = MPI_COMM_WORLD" before the call to
> MPI_COMM_RANK, the output prints properly for me (i.e., I see my hostname).
>
> > This seems odd to me. I haven't passed in MPI_COMM_WORLD as the
> communicator to MPI_Comm_Rank, and yet, it worked and the error code was 0
> (which I'd take as success). Even if you couldn't detect this at compile
> time, I'm surprised it doesn't trigger a run-time error.  Is this the
> correct behavior according to the Standard?
>
> I think you're passing an undefined value, so the results will be
> undefined.
>
> It's quite possible that the comm%mpi_val inside the comm is (randomly?)
> assigned to 0, which is the same value as mpif.f's MPI_COMM_WORLD, and
> therefore your comm is effectively the same as mpi_f08's MPI_COMM_WORLD --
> which is why MPI_COMM_RANK and MPI_COMM_SIZE worked for you.
>
> Indeed, when I run your program, I get:
>
> -
> $ ./foo
> [savbu-usnic-a:31774] *** An error occurred in MPI_Comm_r

Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and other questions

2016-08-21 Thread Ray Sheppard 

Hi All,
  My two cents, in the old days of SGI, their compiler used to 
initialize declared variables, usually to zero.  When users moved to a 
new machine, like a Cray or SP, all hell broke loose because other 
compilers don't.  As a result, almost everyone now gives you a switch to 
have the compiler do it for you.  For example, with Intel (ifort) it is 
-init=zero. They are pretty good about dealing with default 
initializations too.   -fzero-initialized-in-bss will put zero 
intialized variables back in the data section.  With gfortran you pick 
what you want -finit-[integer/real/etc.]= [many choices]. So. the bottom 
line is that if you want a particular behavior, you just need to tell 
the compiler.

  Ray

On 8/21/2016 11:21 PM, Jeff Hammond wrote:



On Sunday, August 21, 2016, Ben Menadue > wrote:


Hi,

In Fortran, using uninitialised variables is undefined behaviour.
In this case, it’s being initialised to zero (either by the
compiler or by virtue of being in untouched memory), and so
equivalent to MPI_COMM_WORLD in OpenMPI. Other MPI libraries don’t
have MPI_COMM_WORLD .eq. 0 and so the same program would fail.
Similarly, if the same memory has previously been stored to (and
so non-zero) and the compiler doesn’t zero-initialise the variable
(most won’t unless you explicitly ask for it), it will fail with
OpenMPI.


Such false successes are a (the?) reason why MPI libraries should not 
define valid handles to default initializers, whether they 
be standardized or implementation-specific...


Jeff

Just keep in mind that the same is true for *all* variables in
Fortran; even integers and reals have undefined value until
they’re first stored to. This can be quite annoying as specifying
the initial value when declaring them also gives them the SAVE
attribute…

Cheers,

Ben

*From:*users [mailto:users-boun...@lists.open-mpi.org
]
*On Behalf Of *Matt Thompson
*Sent:* Sunday, 21 August 2016 3:07 AM
*To:* Open MPI Users >
*Subject:* Re: [OMPI users] mpi_f08 Question: set comm on
declaration error, and other questions

On Fri, Aug 19, 2016 at 8:54 PM, Jeff Squyres (jsquyres)
> wrote:

On Aug 19, 2016, at 6:32 PM, Matt Thompson > wrote:

> > that the comm == MPI_COMM_WORLD evaluates to .TRUE.? I
discovered that once when I was printing some stuff.
>
> That might well be a coincidence. type(MPI_Comm) is not a
boolean type, so I'm not sure how you compared it to .true.
>
> Well, I made a program like:
>
> (208) $ cat test2.F90
> program whoami
>use mpi_f08
>implicit none
>type(MPI_Comm) :: comm
>if (comm == MPI_COMM_WORLD) write (*,*) "I am MPI_COMM_WORLD"
>if (comm == MPI_COMM_NULL) write (*,*) "I am MPI_COMM_NULL"
> end program whoami
> (209) $ mpifort test2.F90
> (210) $ mpirun -np 4 ./a.out
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>
> I think if you print comm, you get 0 and MPI_COMM_WORLD=0
and MPI_COMM_NULL=2 so...I guess I'm surprised. I'd have
thought MPI_Comm would have been undefined until defined.

I don't know the rules here for what happens in Fortran when
comparing an uninitialized derived type.  The results could be
undefined...?


> Instead you can write a program like this:
>
> (226) $ cat helloWorld.mpi3.F90
> program hello_world
>
>use mpi_f08
>
>implicit none
>
>type(MPI_Comm) :: comm
>integer :: myid, npes, ierror
>integer :: name_length
>
>character(len=MPI_MAX_PROCESSOR_NAME) :: processor_name
>
>call mpi_init(ierror)
>
>call MPI_Comm_Rank(comm,myid,ierror)
>write (*,*) 'ierror: ', ierror
>call MPI_Comm_Size(comm,npes,ierror)
>call
MPI_Get_Processor_Name(processor_name,name_length,ierror)
>
>write (*,'(A,X,I4,X,A,X,I4,X,A,X,A)') "Process", myid,
"of", npes, "is on", trim(processor_name)
>
>call MPI_Finalize(ierror)
>
> end program hello_world
> (227) $ mpifort helloWorld.mpi3.F90
> (228) $ mpirun -np 4 ./a.out
>  ierror:0
>  ierror:0
>  ierror:0
>  ierror:0
> Process2 of4 is on compy
> Process1 of4 is on compy
> Process3 of4 is on compy

> Process0 of4 is on copy

That does seem to be odd output.  What is the hostname on your
machine?

Oh well, I (badly) munged the hostname on th

Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and other questions

2016-08-21 Thread Ben Menadue 
Perhaps even better, you could set an invalid default value inside the type 
definition:

 

  type, BIND(C) :: MPI_Comm

integer :: MPI_VAL = some_invalid_value

  end type MPI_Comm

 

Otherwise, they’ll likely be “initialised” to whatever value was already at 
that location in memory – which for stack-allocated variables could easily be a 
valid handle from a previous invocation of that function…

 

Ben

 

From: users [mailto:users-boun...@lists.open-mpi.org] On Behalf Of Jeff Hammond
Sent: Monday, 22 August 2016 1:21 PM
To: Open MPI Users 
Subject: Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and 
other questions

 



On Sunday, August 21, 2016, Ben Menadue mailto:ben.mena...@nci.org.au> > wrote:

Hi,

 

In Fortran, using uninitialised variables is undefined behaviour. In this case, 
it’s being initialised to zero (either by the compiler or by virtue of being in 
untouched memory), and so equivalent to MPI_COMM_WORLD in OpenMPI. Other MPI 
libraries don’t have MPI_COMM_WORLD .eq. 0 and so the same program would fail. 
Similarly, if the same memory has previously been stored to (and so non-zero) 
and the compiler doesn’t zero-initialise the variable (most won’t unless you 
explicitly ask for it), it will fail with OpenMPI.

 

Such false successes are a (the?) reason why MPI libraries should not define 
valid handles to default initializers, whether they be standardized or 
implementation-specific...

 

Jeff

 

Just keep in mind that the same is true for *all* variables in Fortran; even 
integers and reals have undefined value until they’re first stored to. This can 
be quite annoying as specifying the initial value when declaring them also 
gives them the SAVE attribute…

 

Cheers,

Ben

 

From: users [mailto:users-boun...@lists.open-mpi.org 
 ] On Behalf 
Of Matt Thompson
Sent: Sunday, 21 August 2016 3:07 AM
To: Open MPI Users  >
Subject: Re: [OMPI users] mpi_f08 Question: set comm on declaration error, and 
other questions

 

 

On Fri, Aug 19, 2016 at 8:54 PM, Jeff Squyres (jsquyres)  > wrote:

On Aug 19, 2016, at 6:32 PM, Matt Thompson  > wrote:

> > that the comm == MPI_COMM_WORLD evaluates to .TRUE.? I discovered that once 
> > when I was printing some stuff.
>
> That might well be a coincidence.  type(MPI_Comm) is not a boolean type, so 
> I'm not sure how you compared it to .true.
>
> Well, I made a program like:
>
> (208) $ cat test2.F90
> program whoami
>use mpi_f08
>implicit none
>type(MPI_Comm) :: comm
>if (comm == MPI_COMM_WORLD) write (*,*) "I am MPI_COMM_WORLD"
>if (comm == MPI_COMM_NULL) write (*,*) "I am MPI_COMM_NULL"
> end program whoami
> (209) $ mpifort test2.F90
> (210) $ mpirun -np 4 ./a.out
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>  I am MPI_COMM_WORLD
>
> I think if you print comm, you get 0 and MPI_COMM_WORLD=0 and MPI_COMM_NULL=2 
> so...I guess I'm surprised. I'd have thought MPI_Comm would have been 
> undefined until defined.

I don't know the rules here for what happens in Fortran when comparing an 
uninitialized derived type.  The results could be undefined...?


> Instead you can write a program like this:
>
> (226) $ cat helloWorld.mpi3.F90
> program hello_world
>
>use mpi_f08
>
>implicit none
>
>type(MPI_Comm) :: comm
>integer :: myid, npes, ierror
>integer :: name_length
>
>character(len=MPI_MAX_PROCESSOR_NAME) :: processor_name
>
>call mpi_init(ierror)
>
>call MPI_Comm_Rank(comm,myid,ierror)
>write (*,*) 'ierror: ', ierror
>call MPI_Comm_Size(comm,npes,ierror)
>call MPI_Get_Processor_Name(processor_name,name_length,ierror)
>
>write (*,'(A,X,I4,X,A,X,I4,X,A,X,A)') "Process", myid, "of", npes, "is 
> on", trim(processor_name)
>
>call MPI_Finalize(ierror)
>
> end program hello_world
> (227) $ mpifort helloWorld.mpi3.F90
> (228) $ mpirun -np 4 ./a.out
>  ierror:0
>  ierror:0
>  ierror:0
>  ierror:0
> Process2 of4 is on compy
> Process1 of4 is on compy
> Process3 of4 is on compy

> Process0 of4 is on copy

That does seem to be odd output.  What is the hostname on your machine?  

 

Oh well, I (badly) munged the hostname on the computer I ran on because it had 
the IP address within. I figured better safe than sorry and not broadcast that 
out there. :)

 

FWIW, I changed your write statement to:

print *, "Process", myid, "of", npes, "is on", trim(processor_name)

and after I added a "comm = MPI_COMM_WORLD" before the call to MPI_COMM_RANK, 
the output prints properly for me (i.e., I see my hostname).

> This seems odd to me. I haven't passed in MPI_COMM_WORLD as the communicator 
> to MPI_Comm_Rank, and yet, it worked and the error code was 0 (which I'd take 
> as success). Even if you couldn't detect this at compile time, I'm surprised 
> it doesn't trigger a run-time error.  Is this the correct behavior according 
> to the Standard?

I think you're pa