Hi Shintaro,

Thanks for your response. I already have an implementation similar to what you propose, I was just wondering if there was a way to implement it using those unit ids. Apparently not.

Thanks!

Matthieu

From: "Iwasaki, Shintaro" <siwasaki@anl.gov>
Date: Monday, 21 June 2021 at 02:58
To: "discuss@lists.argobots.org" <discuss@lists.argobots.org>
Cc: "Dorier, Matthieu" <mdorier@anl.gov>
Subject: Re: Attribution of ULT ids

Hi, Matthieu

Thank you for your question.

> Is the ABT_unit_id associated to threads and tasks a number that necessarily increases as new threads/tasks are created?

No.  Even in the current implementation, a ULT ID is determined when it is inquired about (e.g., `by ABT_thread_get_id()`), not when a ULT is created.  This "inquiry" timing depends on configuration options. In the future, this ID can be replaced by a "pointer". I do not recommend you rely on the ID to know when ULTs/tasks are created.

> I would like to implement a custom pool that prioritizes running older ULTs over newer ones when possible.

I do not know how strictly you want to control scheduling, but the following might be easy to implement and beneficial.

sched_run():

  while (1) {

    /* Check old_thread_pool first. */

    if (unit = ABT_pool_pop(old_thread_pool)) {

      /* If "unit" yields, it is pushed to old_thread_pool.

       * If you want, you can push it to very_old_thread_pool. */

      ABT_xstream_run_unit(unit, old_thread_pool);

      continue;

    }

    /* Check new_thread_pool if old_thread_pool is empty */

    if (unit = ABT_pool_pop(new_thread_pool))

      /* If "unit" yields, it is pushed to old_thread_pool.

       * Note that Argobots 1.1+ does not need ABT_unit_set_associated_pool()

       * https://github.com/pmodels/argobots/pull/317 */

      ABT_xstream_run_unit(unit, old_thread_pool);

    }

  }

The scheduling can cause a deadlock.  Please check the solution in the discussion below.

Related discussion: https://lists.argobots.org/pipermail/discuss/2020-August/000085.html

Thanks,

Shintaro

---

From: Dorier, Matthieu via discuss <discuss@lists.argobots.org>
Sent: Sunday, June 20, 2021 10:15 AM
To: discuss@lists.argobots.org <discuss@lists.argobots.org>
Cc: Dorier, Matthieu <mdorier@anl.gov>
Subject: [argobots-discuss] Attribution of ULT ids

Hi,

Is the ABT_unit_id associated to threads and tasks a number that necessarily increases as new threads/tasks are created?

I’m asking because I would like to implement a custom pool that prioritizes running older ULTs over newer ones when possible, and one way of knowing which of multiple ULTs is older could be to look at the ABT_unit_id and prioritize ULTs with the smallest id.

Thanks,

Matthieu