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Add work_pool_size, IntRange, item_range_for_worker, and ThreadIndex

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We'll use these later in this PR.
This commit is contained in:
Robert O'Callahan 2026-01-28 18:50:23 +00:00
parent 9e523e2fd7
commit fb24763a15
2 changed files with 64 additions and 0 deletions
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35
kernel/threading.cc
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@ -17,6 +17,20 @@ static int get_max_threads()
return max_threads;
}
static int init_work_units_per_thread_override()
{
const char *v = getenv("YOSYS_WORK_UNITS_PER_THREAD");
if (v == nullptr)
return 0;
return atoi(v);
}
static int get_work_units_per_thread_override()
{
static int work_units_per_thread = init_work_units_per_thread_override();
return work_units_per_thread;
}
void DeferredLogs::flush()
{
for (auto &m : logs)
@ -37,6 +51,14 @@ int ThreadPool::pool_size(int reserved_cores, int max_worker_threads)
#endif
}
int ThreadPool::work_pool_size(int reserved_cores, int work_units, int work_units_per_thread)
{
int work_units_per_thread_override = get_work_units_per_thread_override();
if (work_units_per_thread_override > 0)
work_units_per_thread = work_units_per_thread_override;
return pool_size(reserved_cores, work_units / work_units_per_thread);
}
ThreadPool::ThreadPool(int pool_size, std::function<void(int)> b)
: body(std::move(b))
{
@ -57,4 +79,17 @@ ThreadPool::~ThreadPool()
#endif
}
IntRange item_range_for_worker(int num_items, int thread_num, int num_threads)
{
if (num_threads <= 1) {
return {0, num_items};
}
int items_per_thread = num_items / num_threads;
int extra_items = num_items % num_threads;
// The first `extra_items` threads get one extra item.
int start = thread_num * items_per_thread + std::min(thread_num, extra_items);
int end = (thread_num + 1) * items_per_thread + std::min(thread_num + 1, extra_items);
return {start, end};
}
YOSYS_NAMESPACE_END

29
kernel/threading.h
View file

@ -131,6 +131,11 @@ public:
// The result may be 0.
static int pool_size(int reserved_cores, int max_worker_threads);
// Computes the number of worker threads to use, by dividing work_units among threads.
// For testing purposes you can set YOSYS_WORK_UNITS_PER_THREAD to override `work_units_per_thread`.
// The result may be 0.
static int work_pool_size(int reserved_cores, int work_units, int work_units_per_thread);
// Create a pool of threads running the given closure (parameterized by thread number).
// `pool_size` must be the result of a `pool_size()` call.
ThreadPool(int pool_size, std::function<void(int)> b);
@ -154,6 +159,30 @@ private:
#endif
};
// A range of integers [start_, end_) that can be iterated over with a
// C++ range-based for loop.
struct IntRange {
int start_;
int end_;
struct Int {
int v;
int operator*() const { return v; }
Int &operator++() { ++v; return *this; }
bool operator!=(const Int &other) const { return v != other.v; }
};
Int begin() const { return {start_}; }
Int end() const { return {end_}; }
};
// Divides some number of items into `num_threads` subranges and returns the
// `thread_num`'th subrange. If `num_threads` is zero, returns the whole range.
IntRange item_range_for_worker(int num_items, int thread_num, int num_threads);
// A type that encapsulates the index of a thread in some list of threads. Useful for
// stronger typechecking and code readability.
struct ThreadIndex {
int thread_num;
};
template <class T>
class ConcurrentStack
{