charr_chunking: Tune how parallel work is divided

In charr: String Processing Reimagined for 'ALTREP' Strings

Tune how parallel work is divided

Description

These control how a data-parallel operation cuts its work into chunks once charr_threads() has decided how many threads to use. Neither affects whether threads are used at all, and neither changes any result.

Usage

charr_chunks_per_worker(value = NULL)

charr_min_chunk(value = NULL)

Arguments

value

NULL to query the current setting, or a positive whole number.

Details

Threads draw chunks one at a time rather than taking a fixed slice each, so a thread that finishes a cheap chunk comes back for another. That is what keeps uneven input balanced: element cost is not uniform, and one long string can outweigh a thousand short ones.

charr_chunks_per_worker() sets how many chunks each thread should get, defaulting to 128. Higher values balance skewed input better and cost a little more bookkeeping. charr_min_chunk() sets the smallest number of elements a chunk may hold, defaulting to 256, which stops a large thread count from cutting the work finer than it is worth handing out.

With n elements and w threads the chunk size is ceiling(n / (w * chunks_per_worker)), raised to at least min_chunk and then lowered if needed so that there are never fewer chunks than threads. A short vector therefore still spreads across every thread.

Like charr_threads(), both settings are held in native code rather than in an R option, because they are only ever read there. These accessors are the only way to change them.

Value

The current setting when querying. When setting, the previous value is returned invisibly.

Examples

old <- charr_chunks_per_worker(256)
charr_chunks_per_worker()
charr_chunks_per_worker(old)

charr documentation built on Nov. 7, 2026, 9:06 a.m.