Set the number of threads used by a5R

Controls the number of threads used for parallel processing in vectorised functions. Set to 1 (the default) for sequential processing with zero overhead, or higher for parallel execution via rayon.

Usage

a5_set_threads(n = 1L)

# S3 method for class 'a5_threads'
with(data, expr, ...)

a5_get_threads()

Arguments

n

Integer scalar. Number of threads. Must be >= 1. The value returned by an earlier a5_set_threads() call also works.

data

The value of a5_set_threads().

expr

Code to run with that thread count.

...

Unused.

Value

a5_set_threads(): the previous thread count, invisibly, as an a5_threads object. with(): the value of expr. a5_get_threads(): the current count, an integer scalar.

Details

a5_set_threads() returns the previous thread count, so a change can be scoped to a block of code with with(), as mirai::daemons() is: with(a5_set_threads(4), expr) runs expr on four threads and then restores the previous count, even if expr fails.

Examples

cells <- a5_lonlat_to_cell(runif(1000, -180, 180), runif(1000, -80, 80), 10)
b <- with(a5_set_threads(2), a5_cell_to_boundary(cells))
a5_get_threads()
#> [1] 1