From 8cd42ca38aff422dc9fef2cbe015d8b1963a74bb Mon Sep 17 00:00:00 2001
From: be-marc <marcbecker@posteo.de>
Date: Wed, 13 Dec 2023 15:52:48 +0100
Subject: [PATCH] feat: reduce blas threads to 1

---
 DESCRIPTION | 1 +
 R/worker.R  | 9 +++++++--
 R/zzz.R     | 1 +
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/DESCRIPTION b/DESCRIPTION
index 1f1248aa7..298b875c4 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -56,6 +56,7 @@ Imports:
     parallelly,
     palmerpenguins,
     paradox (>= 0.10.0),
+    RhpcBLASctl,
     uuid
 Suggests:
     Matrix,
diff --git a/R/worker.R b/R/worker.R
index bc45df2b8..324eb7652 100644
--- a/R/worker.R
+++ b/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)) {
diff --git a/R/zzz.R b/R/zzz.R
index caef148c6..1b3991935 100644
--- a/R/zzz.R
+++ b/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}