Implement the remaining GOMP_* functions to support task reductions
in taskgroup, parallel, loop, and taskloop constructs. The unused mem
argument to many of the work-sharing constructs has to do with the
scan() directive/ inscan() modifier. If mem is set, each function
will call KMP_FATAL() and tell the user scan/inscan is unsupported. The
GOMP reduction implementation is kept separate from our implementation
because of how GOMP presents reduction data and computes the reductions.
GOMP expects the privatized copies to be present even after a #pragma
omp parallel reduction(task:...) region has ended so the data is stored
inside GOMP's uintptr_t* data pseudo-structure. This style is tightly
coupled with GCC compiler codegen. There also isn't any init(),
combiner(), fini() functions in GOMP's codegen so the two
implementations were to disparate to try to wrap GOMP's around our own.
Differential Revision: https://reviews.llvm.org/D98806
It is reported that after enabling hidden helper thread, the program
can hit the assertion `new_gtid < __kmp_threads_capacity` sometimes. The root
cause is explained as follows. Let's say the default `__kmp_threads_capacity` is
`N`. If hidden helper thread is enabled, `__kmp_threads_capacity` will be offset
to `N+8` by default. If the number of threads we need exceeds `N+8`, e.g. via
`num_threads` clause, we need to expand `__kmp_threads`. In
`__kmp_expand_threads`, the expansion starts from `__kmp_threads_capacity`, and
repeatedly doubling it until the new capacity meets the requirement. Let's
assume the new requirement is `Y`. If `Y` happens to meet the constraint
`(N+8)*2^X=Y` where `X` is the number of iterations, the new capacity is not
enough because we have 8 slots for hidden helper threads.
Here is an example.
```
#include <vector>
int main(int argc, char *argv[]) {
constexpr const size_t N = 1344;
std::vector<int> data(N);
#pragma omp parallel for
for (unsigned i = 0; i < N; ++i) {
data[i] = i;
}
#pragma omp parallel for num_threads(N)
for (unsigned i = 0; i < N; ++i) {
data[i] += i;
}
return 0;
}
```
My CPU is 20C40T, then `__kmp_threads_capacity` is 160. After offset,
`__kmp_threads_capacity` becomes 168. `1344 = (160+8)*2^3`, then the assertions
hit.
Reviewed By: protze.joachim
Differential Revision: https://reviews.llvm.org/D98838
The basic design is to create an outer-most parallel team. It is not a regular team because it is only created when the first hidden helper task is encountered, and is only responsible for the execution of hidden helper tasks. We first use `pthread_create` to create a new thread, let's call it the initial and also the main thread of the hidden helper team. This initial thread then initializes a new root, just like what RTL does in initialization. After that, it directly calls `__kmpc_fork_call`. It is like the initial thread encounters a parallel region. The wrapped function for this team is, for main thread, which is the initial thread that we create via `pthread_create` on Linux, waits on a condition variable. The condition variable can only be signaled when RTL is being destroyed. For other work threads, they just do nothing. The reason that main thread needs to wait there is, in current implementation, once the main thread finishes the wrapped function of this team, it starts to free the team which is not what we want.
Two environment variables, `LIBOMP_NUM_HIDDEN_HELPER_THREADS` and `LIBOMP_USE_HIDDEN_HELPER_TASK`, are also set to configure the number of threads and enable/disable this feature. By default, the number of hidden helper threads is 8.
Here are some open issues to be discussed:
1. The main thread goes to sleeping when the initialization is finished. As Andrey mentioned, we might need it to be awaken from time to time to do some stuffs. What kind of update/check should be put here?
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D77609
The basic design is to create an outer-most parallel team. It is not a regular team because it is only created when the first hidden helper task is encountered, and is only responsible for the execution of hidden helper tasks. We first use `pthread_create` to create a new thread, let's call it the initial and also the main thread of the hidden helper team. This initial thread then initializes a new root, just like what RTL does in initialization. After that, it directly calls `__kmpc_fork_call`. It is like the initial thread encounters a parallel region. The wrapped function for this team is, for main thread, which is the initial thread that we create via `pthread_create` on Linux, waits on a condition variable. The condition variable can only be signaled when RTL is being destroyed. For other work threads, they just do nothing. The reason that main thread needs to wait there is, in current implementation, once the main thread finishes the wrapped function of this team, it starts to free the team which is not what we want.
Two environment variables, `LIBOMP_NUM_HIDDEN_HELPER_THREADS` and `LIBOMP_USE_HIDDEN_HELPER_TASK`, are also set to configure the number of threads and enable/disable this feature. By default, the number of hidden helper threads is 8.
Here are some open issues to be discussed:
1. The main thread goes to sleeping when the initialization is finished. As Andrey mentioned, we might need it to be awaken from time to time to do some stuffs. What kind of update/check should be put here?
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D77609
This patch adds new API __kmpc_taskloop_5 to accomadate strict
modifier (introduced in OpenMP 5.1) in num_tasks and grainsize
clause.
Differential Revision: https://reviews.llvm.org/D92352
This change introduces the GOMP_taskwait_depend() function. It implements
the OpenMP 5.0 feature of #pragma omp taskwait with depend() clause by
wrapping around __kmpc_omp_wait_deps().
Differential Revision: https://reviews.llvm.org/D87269
Encapsulate GOMP task dependencies in separate class and introduce the
new mutexinoutset dependency type. This separate class allows
future GOMP task APIs easier access to the task dependency functionality
and better ability to propagate new dependency types to all existing GOMP
task APIs which use task dependencies.
Differential Revision: https://reviews.llvm.org/D87267
If the compilation fails, the test is marked as unsupported.
-> This will never change for a specific version of gcc
If the linking fails, the test is marked as expected to fail.
-> This might change as LLVM/OpenMP implements the missing GOMP interface function
Reviewed by: Hahnfeld
Differential Revision: https://reviews.llvm.org/D83077
This is a follow up patch to D64534 (r365963) which removed all OMP
spec versioning within the OpenMP runtime codebase. This patch removes
REQUIRES: openmp-x.y lines from lit tests.
llvm-svn: 366341
Remove all older OMP spec versioning from the runtime and build system.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D64534
llvm-svn: 365963
The omp_taskloop_num_tasks and omp_taskwait have deadlooped
on the NetBSD buildbot previously, practically hanging the host running
it. Disable them until we can find a good solution, or make the kernel
less fragile.
llvm-svn: 361825
Implemented task modifier in two versions - one without taking into account
omp_orig variable (the omp_orig still can be processed by compiler without help
of the library, but each reduction object will need separate initializer with
global access to omp_orig), another with omp_orig variable included into
interface (single initializer can be used for multiple reduction objects of
the same type). Second version can be used when the omp_orig is not globally
accessible, or to optimize code in case of multiple reduction objects
of the same type.
Patch by Andrey Churbanov
Differential Revision: https://reviews.llvm.org/D60976
llvm-svn: 359710
On most platforms, certain compiler and linker flags have to be passed
when using pthreads, otherwise linking against libomp.so might fail with
undefined references to several pthread functions.
Use CMake's `find_package(Threads)` to determine these for standalone
builds, or take them (and optionally modify them) from the top-level
LLVM cmake files.
Also, On FreeBSD, ensure that libomp.so is linked against libm.so,
similar to NetBSD.
Adjust test cases with hardcoded `-lpthread` flag to use the common
build flags, which should now have the required pthread flags.
Reviewers: emaste, jlpeyton, krytarowski, mgorny, protze.joachim, Hahnfeld
Reviewed By: Hahnfeld
Subscribers: AndreyChurbanov, tra, EricWF, Hahnfeld, jfb, jdoerfert, openmp-commits
Tags: #openmp
Differential Revision: https://reviews.llvm.org/D59451
llvm-svn: 357618
Summary:
I have discovered this because i wanted to experiment with
building static libomp (with openmp-4.0 support only)
for debugging purposes.
There are three kinds of problems here:
1. `__kmp_compare_and_store_acq()` simply does not exist.
It was added in D47903 by @jlpeyton.
I'm guessing `__kmp_atomic_compare_store_acq()` was meant.
2. In `__kmp_is_ticket_lock_initialized()`,
`lck->lk.initialized` is `std::atomic<bool>`,
while `lck` is `kmp_ticket_lock_t *`.
Naturally, they can't be equality-compared.
Either, it should return the value read from `lck->lk.initialized`,
or do what `__kmp_is_queuing_lock_initialized()` does,
compare the passed pointer with the field in the struct
pointed by the pointer. I think the latter is correct-er choice here.
3. Tests were not versioned.
They assume that `LIBOMP_OMP_VERSION` is at the latest version.
This does not touch LIBOMP_OMP_VERSION=30. That is still broken.
Reviewers: jlpeyton, Hahnfeld, AndreyChurbanov
Reviewed By: AndreyChurbanov
Subscribers: guansong, jfb, openmp-commits, jlpeyton
Tags: #openmp
Differential Revision: https://reviews.llvm.org/D55496
llvm-svn: 349260
Only supported since GCC 6 and Intel 17.0. However GCC 6.3.0 is
crashing on two of the tests, so disable them as well...
Differential Revision: https://reviews.llvm.org/D50085
llvm-svn: 338720
GCC 4.8.5 defaults to this old C standard. I think we should make the
tests pass a newer -std=c99|c11 but that's too intrusive for now...
Differential Revision: https://reviews.llvm.org/D50084
llvm-svn: 338490
From the bug report, the runtime needs to initialize the nproc variables
(inside middle init) for each root when the task is encountered, otherwise,
a segfault can occur.
Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=36720
Differential Revision: https://reviews.llvm.org/D49996
llvm-svn: 338313
This patch introduces GOMP_taskloop to our API. It adds GOMP_4.5 to our
version symbols. Being a wrapper around __kmpc_taskloop, the function
creates a task with the loop bounds properly nested in the shareds so that
the GOMP task thunk will work properly. Also, the firstprivate copy constructors
are properly handled using the __kmp_gomp_task_dup() auxiliary function.
Currently, only linear spawning of tasks is supported
for the GOMP_taskloop interface.
Differential Revision: https://reviews.llvm.org/D45327
llvm-svn: 330282
Perform a nested CMake invocation to avoid writing our own parser
for compiler versions when we are not testing the in-tree compiler.
Use the extracted information to mark a test as unsupported that
hangs with Clang prior to version 4.0.1 and restrict tests for
libomptarget to Clang version 6.0.0 and later.
Differential Revision: https://reviews.llvm.org/D40083
llvm-svn: 319448
Summary:
Taskloop implementation is extended by using recursive task scheduling.
Envirable KMP_TASKLOOP_MIN_TASKS added as a manual threshold for the user
to switch from recursive to linear tasks scheduling.
Details:
* The calculations for the loop parameters are moved from __kmp_taskloop_linear
upper level
* Initial calculation is done in the __kmpc_taskloop, further range splitting
is done in the __kmp_taskloop_recur.
* Added threshold to switch from recursive to linear tasks scheduling;
* One half of split range is scheduled as an internal task which just moves
sub-range parameters to the stealing thread that continues recursive
scheduling (if number of tasks still enough), the other half is processed
recursively;
* Internal task duplication routine fixed to assign parent task, that was not
needed when all tasks were scheduled by same thread, but is needed now.
Patch by Andrey Churbanov
Differential Revision: https://reviews.llvm.org/D35273
llvm-svn: 308338
Added test kmp_task_reduction_nest.cpp which has an example of
possible compiler codegen.
Differential Revision: https://reviews.llvm.org/D29600
llvm-svn: 295343
Consider the following code:
int dep;
#pragma omp target nowait depend(out: dep)
{
sleep(1);
}
#pragma omp task depend(in: dep)
{
printf("Task with dependency\n");
}
printf("Doing some work...\n");
In its current state the runtime will block on the second task and not
continue execution.
Differential Revision: https://reviews.llvm.org/D23116
llvm-svn: 277992
Consider the following code which may be executed by a serial team:
int dep;
#pragma omp target nowait depend(out: dep)
{
sleep(1);
}
#pragma omp task depend(in: dep)
{
#pragma omp target nowait
{
sleep(1);
}
}
Here the explicit task may not be freed until the nested proxy task has
finished. The current code hasn't considered this and called __kmp_free_task
anyway which triggered an assert because of remaining incomplete children:
KMP_DEBUG_ASSERT( TCR_4(taskdata->td_incomplete_child_tasks) == 0 );
Differential Revision: https://reviews.llvm.org/D23115
llvm-svn: 277991
Peyton, Jonathan L