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Create Chunks of Index Vectors

Source: R/make_chunks.R
make_chunks.Rd

This is an internal function.

Usage

make_chunks(nelements, nworkers, scheduling = 1, chunk_size = NULL)

Arguments

nelements

(integer) Total number of elements to iterate over.

nworkers

(integer) Number of workers available.

scheduling

(numeric) A strictly positive scalar. Only used if argument chunk_size is NULL.

chunk_size

(numeric) The maximum number of elements per chunk, or NULL. If NULL, then the chunk sizes are given by the scheduling argument.

Value

A list of chunks, where each chunk is an integer vector of unique indices in [1, nelements]. The union of all chunks holds nelements elements and equals 1:nelements. If nelements == 0, then an empty list is returned.

Control processing order of elements

Attribute ordering of chunk_size or scheduling can be used to control the ordering the elements are iterated over, which only affects the processing order not the order values are returned. This attribute can take the following values:

  • index vector - an numeric vector of length nelements specifying how elements are remapped

  • function - an function taking one argument which is called as ordering(nelements) and which must return an index vector of length nelements, e.g. function(n) rev(seq_len(n)) for reverse ordering.

  • "random" - this will randomize the ordering via random index vector sample.int(nelements).