H5Part development and discussion

[Gsell Achim <achim.gsell AT gmail.com>]

Hi Matthew

On Oct 26, 2012, at 12:32 AM, Matthew Bettencourt wrote:

> Also, H5PartSetView doesn't work if one has less than 1 part/proc, 
> example...
> 
> my_pid is rank, and num_procs is 3.  s = {0,0,0}, e={-1,-1,2} and nproc2 
> should be {0,0,2} but it is {2,2,2}
> 
> 
>   h5part_int64_t npart = H5PartGetNumParticles(file_);  //<<<<<<<<this 
> returns 2
> 
>   h5part_int64_t npart_per_proc = npart/num_procs;
>   h5part_int64_t npart_remainder = npart%num_procs;
> 
> 
>   h5part_int64_t s = npart_per_proc*my_pid;
>   h5part_int64_t e= npart_per_proc*(my_pid+1)-1;
>   if ( my_pid == num_procs-1 )
>     e += npart_remainder;
> 
> 
>   npart = e-s+1;
>   if (H5PartSetView(file_, s, e) != 0 )
>     error_out("Cannot set file view for h5part file\n");
> 
>   h5part_int64_t npart2 =  H5PartGetNumParticles(file_);  //<<<<<<<<<<<<<  
> This returns 2
> 
>   assert (npart == npart2);

This is actually an undocumented feature. H5PartSetView was not designed to 
select zero particles. If you pass -1 as end, this will not be interpreted as 
"select zero particles" but as "select all particles from the value given in 
start to the end. So if you do something like

H5PartSetView (f, 0, -1); 

you actually select all particles in the dataset. We will improve the 
documentation in this point. A workaround is to use

H5PartSetViewIndices (f, NULL, 0);

if you want to select zero particles.

> 
> 
> -------- Original Message --------
> Subject:      H5PartSetCanonicalView
> Date: Thu, 25 Oct 2012 16:22:00 -0600
> From: Matthew Bettencourt <mbetten AT sandia.gov>
> To:   h5part AT lists.psi.ch
> 
> It appears that H5PartSetCanonicalView does not work correctly if you 
> have fewer particles that you have processors.  I have 3 procs and 2 
> particles.
> 
>   if (H5PartSetCanonicalView(file_) != 0 )
>     error_out("Cannot set file view for h5part file\n");
>   h5part_int64_t npart = H5PartGetNumParticles(file_);
> 
> returns an npart equal to 2 and doesnt trip the error.

OK, we will check this.


Achim