List of features to deprecate

[halimamer]

There are a number of features that were originally added to the public Argobots API that proved unnecessary or break some intentions. This issue keeps track of these features that will be considered for deprecation in the future.

1. User-provided stacks (c.f. threads with user-provided stacks: Need stack free hook #16)
2. Allowing busy-waiting, i.e., blocking, inside a tasklet (c.f. Disallow any form of blocking behaviour in tasklets #15)
3. The event interface

[carns]

FWIW, the Mochi project doesn't use either of these features; we wouldn't notice them being removed :)

[shintaro-iwasaki]

ABT_xstream_create_with_rank:
it does not seem very necessary. It just makes the ES management complicated.

ABT_thread_retain/ABT_thread_release/ABT_task_retain/ABT_task_release:

1. They are totally broken now.
2. There's no good fix without hurting performance (these features force atomic operations (just for counters) to the runtime).

ABT_thread_set_arg/ABT_thread_get_arg/ABT_task_get_arg/ABT_self_set_arg/ABT_self_get_arg:

1. The runtime cannot guarantee when the arguments are read by ULTs.
2. Currently this functionality is used to embed user data (a pointer) to a ULT, but again, it is not the intended use. We should create ABT_thread_set_data instead.

[pavanbalaji]

@shintaro-iwasaki It might be useful to create a PR removing these features and have @carns and others (e.g., folks from the DAOS project) approve it.

[carns]

FWIW we don't use any of those specific functions, but the PR approach seems reasonable to me.

[shintaro-iwasaki]

The information is obsolete, so I will close this issue. The following is the summary.

1. [User-provided stacks] Argobots continues to support it.
   It is useful in some cases (ULT stack allocation method to address overrun scenario #274)

2. [Allowing busy-waiting inside a tasklet] Argobots continues to support it. Argobots 2.0 allows more.
   All blocking operations support tasklets from Argobots 2.0. It is the user's responsibility to avoid a deadlock.

3. [The event interface] Argobots 1.0 has removed it
   It was unused.

4. [ABT_xstream_create_with_rank()] Argobots continues to support it.
   It's mostly useless but we cannot easily remove it. ABT_xstream_set_rank() should be also problematic, but at least we can keep supporting it without any performance overheads.

5. [ABT_thread_retain(), ABT_thread_release(), ABT_task_retain(), ABT_task_release()] Argobots 1.0 has removed them.
   They were completely broken.

6. [ABT_thread_set_arg(), ABT_thread_get_arg(), ABT_task_get_arg(), ABT_self_set_arg(), ABT_self_get_arg()] Argobots continues to support them.
   Although it is very error-prone, it is the user's responsibility to maintain the argument properly.

Other deprecated features are explicitly noted in the specification. Most of them are deprecated from Argobots 2.0. Note that Argobots 1.1 will not change the existing Argobots 1.0 behavior except for a few corner cases (e.g., ABT_barrier_create() with num_waiters = 0).