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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "dual_merge_director.h"
namespace vespalib {
bool
DualMergeDirector::MergeState::merge()
{
if (second.thread_id < first.thread_id) {
std::swap(first, second);
}
first.source->merge(*second.source);
second = TaggedSource();
return (state != LAST);
}
void
DualMergeDirector::MixedMergeStateExchanger::mingle()
{
out(0) = MergeState(last ? MergeState::LAST : MergeState::TYPEA,
in(0).first, in(1).first);
out(1) = MergeState(last ? MergeState::LAST : MergeState::TYPEB,
in(0).second, in(1).second);
}
void
DualMergeDirector::MergeStateExchanger::mingle()
{
bool last = (--remaining == 0);
size_t dst = (in(0).first.thread_id < in(1).first.thread_id) ? 0 : 1;
out(dst) = MergeState(last ? MergeState::LAST : in(0).state,
in(dst).first, in(1 - dst).first);
}
DualMergeDirector::DualMergeDirector(size_t num_threads)
: _num_threads(num_threads),
_mixedExchanger(num_threads == 2),
_typeAExchanger((num_threads - 1) / 2),
_typeBExchanger((num_threads - 1) / 2)
{
}
DualMergeDirector::~DualMergeDirector() {}
void
DualMergeDirector::dualMerge(size_t thread_id, Source &typeA, Source &typeB)
{
if (_num_threads == 1) {
return;
}
if (((_num_threads % 2) == 1) && ((thread_id + 1) == _num_threads)) {
_typeAExchanger.rendezvous(MergeState(MergeState::TYPEA,
TaggedSource(thread_id, typeA)));
_typeBExchanger.rendezvous(MergeState(MergeState::TYPEB,
TaggedSource(thread_id, typeB)));
return;
}
MergeState state(MergeState::MIXED, TaggedSource(thread_id, typeA),
TaggedSource(thread_id, typeB));
state = _mixedExchanger.rendezvous(state);
MergeStateExchanger &exchanger = (state.state == MergeState::TYPEA) ?
_typeAExchanger : _typeBExchanger;
while (state.merge()) {
state = exchanger.rendezvous(state);
if (state.state == MergeState::EMPTY) {
return;
}
}
}
} // namespace vespalib
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