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Render many scenes in parallel

Source: R/output.R
render_all.Rd

Renders a list of independent scenes across cores. This is embarrassingly parallel — one whole scene per worker, nothing shared — which is why it exists while tiling a single raster across threads does not: that needs synchronised access to one pixmap and is declined in PERFORMANCE.md.

Usage

render_all(scenes, paths, workers = NULL, ...)

Arguments

scenes

A named or unnamed list of scenes.

paths

Output paths, one per scene. The format of each comes from its extension, exactly as in render(). When scenes is named and paths is a single directory, files are named after the list.

workers

Number of parallel workers. Defaults to one per available core, capped at the number of scenes.

...

Passed to render() for every scene.

Value

The paths written, invisibly.

Details

The saving is real when the scenes are substantial and there are several of them. For a handful of small figures the process/thread overhead dominates and a plain lapply(scenes, render) is as fast; this reports enough to tell.

See also

render(), pdf_pages()

Examples

scenes <- list(
  a = vl_scene(3, 2, dpi = 96) |> draw(circle_grob(gp = vl_gpar(fill = "tomato"))),
  b = vl_scene(3, 2, dpi = 96) |> draw(rect_grob(gp = vl_gpar(fill = "steelblue")))
)
render_all(scenes, file.path(tempdir(), c("a.png", "b.png")))