feat: reduce blas threads to 1

DESCRIPTION

@@ -56,6 +56,7 @@ Imports:
     parallelly,
     palmerpenguins,
     paradox (>= 0.10.0),
+    RhpcBLASctl,
     uuid
 Suggests:
     Matrix,

R/worker.R

@@ -224,8 +224,13 @@ workhorse = function(iteration, task, learner, resampling, param_values = NULL,
     pb(sprintf("%s|%s|i:%i", task$id, learner$id, iteration))
   }
 
-  # reduce data.table threads to 1
-  if (!is_sequential) setDTthreads(1)
+  # reduce data.table and blas threads to 1
+  if (!is_sequential) {
+    setDTthreads(1, restore_after_fork = TRUE)
+    old_blas_threads = blas_get_num_procs()
+    on.exit(blas_set_num_threads(old_blas_threads), add = TRUE)
+    blas_set_num_threads(1)
+  }
 
   # restore logger thresholds
   for (package in names(lgr_threshold)) {

R/zzz.R

@@ -10,6 +10,7 @@
 #' @importFrom uuid UUIDgenerate
 #' @importFrom parallelly availableCores
 #' @importFrom future nbrOfWorkers plan
+#' @importFrom RhpcBLASctl blas_set_num_threads
 #'
 #' @section Learn mlr3:
 #' * Book on mlr3: \url{https://mlr3book.mlr-org.com}