parquet_set_prefetch_threads Subroutine

public subroutine parquet_set_prefetch_threads(n)

Sets the cap on how many threads parquet_table%prefetch/%materialize_all may use to read several columns at once, each on its own reader.

Read per prefetch, so it takes effect immediately. 0 restores automatic behaviour. The value is a cap: the table never uses more threads than OpenMP offers, so setting this higher than OMP_NUM_THREADS changes nothing. 1 makes the prefetch serial, which is also what happens automatically whenever the parallel path is not applicable.

Arguments

    subroutine parquet_set_prefetch_threads(n)
        integer, intent(in) :: n !! thread cap, or 0 for automatic; must be >= 0.

        if (n < 0) error stop "parquet_set_prefetch_threads: n must be >= 0 (0 means automatic)"
        cfg_prefetch_threads = n
    end subroutine parquet_set_prefetch_threads