Linux 64bits vs 32bits?

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Torben
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12 years 11 months ago - 12 years 11 months ago #6318 by Torben

Linux 64bits vs 32bits? was created by Torben

Hello,

I am considering upgrading to a x86_64 system in order to run a contemporary Salome-MECA. Is there any performance related change to expect due to the 64bits system compared to 32bits?

Thanks for your input.

Edit:

After googling a bit more I found this benchmark for floating points operations:

illustration taken from here: www.phoronix.com
So it seems to work better with _64bits all other equal. However If You have experience to share, please do.

Last edit: 12 years 11 months ago by Torben.

Torben
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12 years 10 months ago - 12 years 10 months ago #6337 by Torben

Replied by Torben on topic Re: Linux 64bits vs 32bits?

For your information I just did a testcase. Exact same hardware (dual boot, actually) and 3GB RAM. Clearly this is not enough to include the benefits of the higher address space. My x64 test system is booted on a 16GB USB stick so to filter out the inferior disc performance the job was executed on the hard disk in both cases.

Size of the job can be described by:

--- NOMBRE TOTAL DE NOEUDS :        60095  DONT :        35768 
  NOEUDS "LAGRANGE"
 --- NOMBRE TOTAL D'EQUATIONS :       157676
 --- TAILLE DU PROFIL MORSE DE LA TRIANGULAIRE SUPERIEURE (FORMAT SCR):      4570293
 --- DONC LA TAILLE DE LA MATRICE EST:
 --- EN SYMETRIQUE     NNZ=      4570293
 --- EN NON SYMETRIQUE NNZ=      8982910

Run 1: Linux Mint 9, x86_32, SALOME-MECA-2010.2-LGPL-i386, Timings:

********************************************************************************
 * COMMAND                  :       USER :     SYSTEM :   USER+SYS :    ELAPSED *
 ********************************************************************************
 * init (jdc)               :       2.40 :       0.23 :       2.63 :       3.85 *
 *  . compile               :       0.00 :       0.00 :       0.00 :       0.00 *
 *  . exec_compile          :       0.22 :       0.01 :       0.23 :       0.23 *
 *  . report                :       0.02 :       0.00 :       0.02 :       0.01 *
 *  . build                 :       0.00 :       0.00 :       0.00 :       0.00 *
 * DEBUT                    :       0.03 :       0.05 :       0.08 :       0.09 *
 * LIRE_MAILLAGE            :       0.15 :       0.00 :       0.15 :       0.35 *
 * CREA_MAILLAGE            :       0.48 :       0.00 :       0.48 :       0.52 *
 * AFFE_MODELE              :       0.12 :       0.00 :       0.12 :       0.36 *
 * DEFI_MATERIAU            :       0.01 :       0.00 :       0.01 :       0.00 *
 * AFFE_MATERIAU            :       0.01 :       0.00 :       0.01 :       0.01 *
 * AFFE_CARA_ELEM           :       0.14 :       0.00 :       0.14 :       0.17 *
 * AFFE_CHAR_MECA           :       2.57 :       0.01 :       2.58 :       2.70 *
 * MECA_STATIQUE            :      29.38 :       3.21 :      32.59 :      40.25 *
 * CALC_ELEM                :       5.33 :       0.02 :       5.35 :       5.43 *
 * CALC_NO                  :       2.91 :       0.06 :       2.97 :       2.94 *
 * IMPR_RESU                :       1.29 :       0.09 :       1.38 :       1.45 *
 * FIN                      :       0.07 :       0.18 :       0.25 :       1.41 *
 *  . part Superviseur      :       2.44 :       0.28 :       2.72 :       4.12 *
 *  . part Fortran          :      42.45 :       3.57 :      46.02 :      55.57 *
 ********************************************************************************
 * TOTAL_JOB                :      44.89 :       3.85 :      48.74 :      59.69 *
 ********************************************************************************

Run 2: Linux Mint 9, x86_64, SALOME-MECA-2010.2-LGPL-x86_64, Timings:

********************************************************************************
 * COMMAND                  :       USER :     SYSTEM :   USER+SYS :    ELAPSED *
 ********************************************************************************
 * init (jdc)               :       2.26 :       0.32 :       2.58 :       2.59 *
 *  . compile               :       0.00 :       0.00 :       0.00 :       0.00 *
 *  . exec_compile          :       0.19 :       0.04 :       0.23 :       0.23 *
 *  . report                :       0.02 :       0.00 :       0.02 :       0.02 *
 *  . build                 :       0.00 :       0.00 :       0.00 :       0.00 *
 * DEBUT                    :       0.03 :       0.07 :       0.10 :       0.10 *
 * LIRE_MAILLAGE            :       0.10 :       0.00 :       0.10 :       0.11 *
 * CREA_MAILLAGE            :       0.42 :       0.00 :       0.42 :       0.42 *
 * AFFE_MODELE              :       0.05 :       0.00 :       0.05 :       0.03 *
 * DEFI_MATERIAU            :       0.00 :       0.00 :       0.00 :       0.00 *
 * AFFE_MATERIAU            :       0.03 :       0.00 :       0.03 :       0.02 *
 * AFFE_CARA_ELEM           :       0.25 :       0.00 :       0.25 :       0.16 *
 * AFFE_CHAR_MECA           :       2.12 :       0.01 :       2.13 :       2.14 *
 * MECA_STATIQUE            :      22.54 :       1.70 :      24.24 :      23.24 *
 * CALC_ELEM                :       3.59 :       0.00 :       3.59 :       3.59 *
 * CALC_NO                  :       2.20 :       0.01 :       2.21 :       2.21 *
 * IMPR_RESU                :       1.90 :       0.03 :       1.93 :       1.93 *
 * FIN                      :       0.12 :       0.34 :       0.46 :       0.47 *
 *  . part Superviseur      :       2.31 :       0.39 :       2.70 :       2.71 *
 *  . part Fortran          :      33.31 :       2.09 :      35.40 :      34.31 *
 ********************************************************************************
 * TOTAL_JOB                :      35.62 :       2.48 :      38.10 :      37.02 *
 ********************************************************************************

So clearly there is a performance improvement by using 64bits systems and versions of Salome-MECA. Even for a "small" job not even close to the 4GB address space limitation a factor of improvement of 1,28 was found.

There are oher challenges of x86_64 systems, but if Aster performance matters it seems worth considering. What puzzles me a bit though is that if I test the total execution tlme from hitting the "RUN" button in Salome-MECA until the run status changes away from RUNNING in the object browser, the performance difference is much less obvious as the total elapsed time measured with a stop watch is around 85 seconds in either case.

Last edit: 12 years 10 months ago by Torben.

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