http://www.mcs.anl.gov/research/projects/mpi/usingmpi2/examples/starting/main.htm


/* example of sequential Unix write into a common file */ 

mpirun -np 4 ./io1


/* example of parallel Unix write into separate files */ 

mpirun -np 4 ./io2

/* example of parallel MPI write into separate files */ 

mpirun -np 4 ./io3


/* example of parallel MPI write into a single file */ 

mpirun -np 4 ./io4


/* example of parallel MPI write into a single file (arbitrary num of procs) */ 

mpirun -np 4 ./io5

/* parallel MPI read with arbitrary number of processes*/ 

mpirun -np 4 ./io6




######################

python
http://chrisjbutler.wordpress.com/2010/09/23/mpi4py-parallel-io-example/

# all in one
mpirun -np 4 ./io4.py


# all in all
mpirun -np 4 ./io3.py


1) les slaves envoient tout au master       (avec MPI/IO  ?)
2) les slaves écrivent leur fichier         (avec MPI/IO ok)
3) les slaves écrivent dans un meme fichier (avec MPI/IO ok)


######################

nouvelle fct

io.ReadBlock		-> io.readblock
			-> mpi_ReadAndSendBlock

io.ReadDataBlock	-> io.readblock
			-> mpi_ReadAndSendArray



io.WriteArray		-> writeblock
			-> mpi_GatherAndWriteArray
io.WriteBlock


!!! (1)
!!! use npart, not good !!!
!!! si on lit pos, et que pos à plusieurs types,
!!! on doit distribuer
!!! -> il faut faire plusieurs lecture, sans header

!!! (2)
!!! si mpi4py n'existe pas, il faut que ça marche...



new function:
 - fct that write a simple header
 - may add header
 
 - master read a block and send it
 - master gather a block and write it
 
 - read an array and send it
 - write an array and send it
 


# problème sphecifique pour gadget

pos
  
  - gas
  - stars
  - halo
  
on veut :

  header		t0
  pos-gas		t0	
  pos-gas		t1
  pos-gas		t2
  pos-stars		t0
  pos-stars		t1
  pos-stars		t2
  pos-halo		t0
  pos-halo		t1
  pos-halo		t2
  header  		t0
  
  WriteGadgetBlock(pos,npart)
  
  WriteGadgetBlock
    WriteHeader
    
    WriteArray(pos[])    
    WriteArray(pos[])
    WriteArray(pos[])

    WriteHeader