Enable Shared-Memory Backend for an MVPA Model Spec

Prepares the dataset for shared-memory access and tags the model specification so that mvpa_iterate uses the shard backend instead of the default furrr pipeline.

Usage

use_shard(mod_spec)

Arguments

mod_spec

A model specification created by mvpa_model (or any constructor that produces an object inheriting from "model_spec").

Value

A copy of mod_spec with class "shard_model_spec" prepended and a $shard_data list attached.

Details

This is an experimental feature. It requires the shard package and a platform that supports POSIX shared memory (shm_open).

Examples

if (requireNamespace("shard", quietly = TRUE)) {
  ds <- gen_sample_dataset(c(4, 4, 4), 24, nlevels = 2, blocks = 3)
  cval <- blocked_cross_validation(ds$design$block_var)
  mspec <- mvpa_model(load_model("corclass"), ds$dataset, ds$design,
                      "classification", crossval = cval)
  mspec <- use_shard(mspec)
  results <- run_searchlight(mspec, radius = 2, method = "randomized",
                             niter = 1)
  shard_cleanup(mspec$shard_data)
}
#> INFO [2026-10-16 11:46:46] shard backend: preparing shared memory for dataset (mvpa_image_dataset, mvpa_dataset, list)
#> INFO [2026-10-16 11:46:46] shard backend [volumetric]: shared 24 x 64 matrix (64 masked voxels)
#> INFO [2026-10-16 11:46:46] searchlight engine: general-purpose iterator (no eligible fast path)
#> INFO [2026-10-16 11:46:46] Running randomized searchlight with radius = 2 and niter = 1
#> INFO [2026-10-16 11:46:46] Starting randomized searchlight analysis:
#> INFO [2026-10-16 11:46:46] - Radius: 2
#> INFO [2026-10-16 11:46:46] - Iterations: 1
#> INFO [2026-10-16 11:46:46] 
#> Iteration 1/1
#> INFO [2026-10-16 11:46:46] Using automatic searchlight batch size 8 for 8 centers (memory budget 512.0 MiB).
#> INFO [2026-10-16 11:46:46] 
#> MVPA Iteration Complete
#> - Total ROIs: 8
#> - Processed: 8
#> - Skipped: 0
#> INFO [2026-10-16 11:46:46] searchlight (randomized): 8 ROIs processed (success=7, errors=1)
#> WARN [2026-10-16 11:46:46] searchlight (randomized): 1 of 8 ROIs failed (12.5%)
#> WARN [2026-10-16 11:46:46]   - [1 ROIs] error: less than 2 features