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Re: Question about memory used by PetsC Objects

Barry,

I thank you for your help. So I tried to apply the functions. It seems that PetscMemoryGetCurrentUsage() gives the total amount of memory allocated at the point of the program where it is placed. But, if a object is deallocated, PetscMemoryGetCurrentUsage() doesn't take it.

I would like to try PetscMemoryGetMaximumUsage() at the end of the program hoping it gives me the maximum memory used by my program but there are problems. When I put PetscMemoryGetMaximumUsage(), I've this error at the execution:

[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Object is in wrong state!
[0]PETSC ERROR: To use this function you must first call PetscMemorySetGetMaximumUsage()!

So I put PetscMemorySetGetMaximumUsage() before, but at linking, it didn't find PetscMemorySetGetMaximumUsage in the petsc libraries. I thought I made a bad install but when I tried on another machine, I've the same problem.

Best regards,

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NGUYEN Anh-Khai Laurent
Equipe Support Utilisateur

Email    :    laurent.nguyen@xxxxxxxx
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Barry Smith a écrit : 
  Laurent,

   The memory usage printed with -log_summary is not correct.
Much of the memory used is not printed out.

   You can use PetscMemoryGetCurrentUsage() and PetscMemoryGetMaximumUsage()
in your code before and after creating a filling in PETSc objects
to see how much memory they are used. You can also use PetscMallocDump()
at any point to see exactly where in PETSc and how much all of PETSc's
memory was allocated.

   Barry


On Thu, 12 Apr 2007, Laurent Nguyen wrote:

Hi,

I'm a Petsc user, but I'm beginning to use petsc in a supercomputation
context. So, I'm trying parallel versions of my old mono-processed programs.
But I've some difficulties to determine how much memory my program use. (I
give a little example). In this example on one processor (with these command
line arguments: -mat_type mpiaij -pc_type none -log_summary), I created one
mpiaij matrix (size = 500*500) and two vectors (size = 500). I've this
information from output:

  Matrix Object:
    type=mpiaij, rows=250000, cols=250000
    total: nonzeros=749996, allocated nonzeros=1750000

To me, there is an array of 1750000 double precision number of 8 bytes =
14000000 bytes (14Mo).

Same for vectors: 2*8*250000 = 4 Mo

But in the log summary, I've:

Memory usage is given in bytes:

Object Type          Creations   Destructions   Memory  Descendants' Mem.

--- Event Stage 0: Main Stage

              Viewer     1              1          0     0
           Index Set     2              2        672     0
                 Map    16             16       4992     0
                 Vec    10             10    2006576     0
         Vec Scatter     1              1          0     0
              Matrix     3              3       1068     0
       Krylov Solver     1              1      17208     0
      Preconditioner     1              1          0     0
=============================================================

I don't understand this output...If you have some documentation about how
Petsc deals with memory or if you can explain, I would be very interested.

This is a problem because I'm working on IBM SP4, and I've limitations of
memory (700mb for data and 700mb for stack). I think the objects created by
Petsc is created in the stack memory, but as I cannot determine exactly the
memory usage, I cannot verify.

Thank you for your advices,

Best regards