[OpenMP] Simplify parallel reductions (#70983)
A lot of the code was from a time when we had multiple parallel levels. The new runtime is much simpler, the code can be simplified a lot which should speed up reductions too.
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A lot of the code was from a time when we had multiple parallel levels. The new runtime is much simpler, the code can be simplified a lot which should speed up reductions too.
mentioned in commit db37d25c