Accéder au contenu.
Menu Sympa

starpu-devel - [Starpu-devel] A question regarding the STARPU_REDUX flag

Objet : Developers list for StarPU

Archives de la liste

[Starpu-devel] A question regarding the STARPU_REDUX flag


Chronologique Discussions 
  • From: Mirko Myllykoski <mirkom@cs.umu.se>
  • To: starpu-devel@lists.gforge.inria.fr
  • Subject: [Starpu-devel] A question regarding the STARPU_REDUX flag
  • Date: Wed, 8 Apr 2020 11:06:31 +0200
  • Authentication-results: mail2-smtp-roc.national.inria.fr; spf=None smtp.pra=mirkom@cs.umu.se; spf=Pass smtp.mailfrom=mirkom@cs.umu.se; spf=None smtp.helo=postmaster@mail.cs.umu.se
  • Ironport-phdr: 9a23:urcc/BUmJBc1pf2IIDnHf1wwjWzV8LGtZVwlr6E/grcLSJyIuqrYbB2Ht8tkgFKBZ4jH8fUM07OQ7/m9HzVfqs/Z+DBaKdoQDkND0Z1X1yUbQ+e7SmTDZMbwaCI7GMkQHHRExFqcdXZvJcDlelfJqWez5zNBUj/2NA5yO/inUtWK15f/2O+94YDcbBtVjzShf7xyMA+2rQLMvcUKnIduMKk8xgbJr3dSZuhbx2xkKU+Pkx3h4su84INv/z5ftv48+MNMS7n2c7g9QbdFEDkoLmc56dHkuhXEUQaB/GYXXH8MkhpPDQjF7RX6UYn0vyDnqOdz2zSUMNPvQ7wsVjus86lkSBnziCcaLDE5633YitZxjK1Avh2soQF0zpPOb4GUMPp+eb7dfc8fSGFcUMtdSzBND4WhZIYJEuEPP/tXr5PlqlUQrRWwGA6sCuDhxDBGiXD5waI03v89EQzFxgEsA84CvXrWodjzKawcUfq1zK7NzTjbaP1W2C396IvPchs8pv+NXbZwcc7RyEksEAPFlVaQqY34ND6S0+QNsnKb7+lnVeKqkGMotxpxriKyxscpl4nFnJkVxU7d+Ch/3Y07K9q4SEthbt6lFptdryCaN41sQsMjWW5koig6yqcetZ6meSgK1Y4rxwXBZPGBboOG4QrjWf6MLTp2mH5pYqyzihi2/ES6xeDwStO43EhKoyZdjNXAqmwB2wHW58SZVvdx4lmt1DOP2g/J9O5JI0U5mKXFJJI/w7M9k5gevVjdESDqnUj6kqCbels69uWt8evof7brqYKZOoJ0lg3zPKQjl8qiCuoiKAcORXKU+eGk2b3j40L5RLJKg+UzkqbDsZDaId4XqbKiAwNPz4Yj7gu/Ay290NsGhXUHLVRFdwybj4XxJl3DLuz0Ae2hj1milDpn3f/LMqH7DpnTLnXPiLLhcqx8605Yxgoz19df55dMB7EEIfLzQEzxtNvdDhIiLwO02PzrCMh41oMDQ26PGbGWPLvIsVCU/uIvP/WMZIgNtTbmN/gq/eTujWckmVMEYKamw4UXZ268Hvl9J0WZYGHsgssaEWsQsQo+QuvqiEeNUTFNfXqyXqQ85is6CI28F4vDSJqt0/S923KgApRMfn0DBl2SHHPAc4SfR+xKZyyVOMBs1D0CT7moDYE7hj+0swqv7rt9Le2c3zwcsYPg08N25qWHkBAo9jtxJ8+GlXyIUidvkzVbFHcNwKljrBklmR+42q9ijqkATIAB17ZySg4/cKXk4aliEdmrA1DKZZGUTUvgWdj0WWhgHOJ0+McHZgNGI/vnixnC2ySwBLpMzu6AH9op97+axHWjfp8gmUaD77EoihwdeuUKNWCigfchpQ3aBoqPmF7fiqO3M78RjnbA
  • List-archive: <http://lists.gforge.inria.fr/pipermail/starpu-devel/>
  • List-id: "Developers list. For discussion of new features, code changes, etc." <starpu-devel.lists.gforge.inria.fr>
  • Organization: Umeå University / HPC2N

Hi,

I have a question regarding STARPU_REDUX flag.

I am confused over the following two statement in the StarPU Handbook:

a) "StarPU provides a mode STARPU_REDUX, which permits to optimize this case: it will allocate a buffer on each memory node, and accumulate intermediate results there. When the data is eventually accessed in the normal mode STARPU_R, StarPU will collect the intermediate results in just one buffer." [1]

b) "Set the codelets to be used for handle when it is accessed in the mode STARPU_REDUX. Per-worker buffers will be initialized with the codelet init_cl, and reduction between per-worker buffers will be done with the codelet redux_cl." [2]

My understanding is the following:

* Statement (a) states that StarPU maintains a reduction buffer for each *memory node*. That is, in shared memory configuration, there is going to be just one reduction buffer and all tasks that access a STARPU_REDUX handle are executed sequentially.

* Statement (b) states that StarPU maintains a reduction buffer for each *worker*. That is, in shared memory configuration, there is going to be several reduction buffers and all tasks that access a STARPU_REDUX handle are executed in parallel.

Which one of these these statements is correct? I am getting results that seem to indicate that the statement (a) is correct.

Best regards,
Mirko Myllykoski

[1]: http://starpu.gforge.inria.fr/doc/html/DataManagement.html#DataReduction
[2]: http://starpu.gforge.inria.fr/doc/html/group__API__Data__Management.html#ga1f5ba1c1cfefc1f81a4095cf3c213e54

--
By sending an email to Umeå University, the University processes your personal data. For more information, please read: https://www.umu.se/en/gdpr




Archives gérées par MHonArc 2.6.19+.

Haut de le page