From 49a137ca2468e4f30afe10c2ceb285ac1843cf9a Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <4643818-rmlarsen1@users.noreply.gitlab.com>
Date: Sat, 28 Mar 2026 16:10:04 -0700
Subject: [PATCH] CI: limit NVHPC build parallelism to avoid OOM kills

libeigen/eigen!2353

Co-authored-by: Rasmus Munk Larsen <rmlarsen@gmail.com>
---
 ci/build.linux.gitlab-ci.yml     | 3 +++
 ci/scripts/build.linux.script.sh | 8 +++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/ci/build.linux.gitlab-ci.yml b/ci/build.linux.gitlab-ci.yml
index e0075eaa8..63b905dc5 100644
--- a/ci/build.linux.gitlab-ci.yml
+++ b/ci/build.linux.gitlab-ci.yml
@@ -172,6 +172,9 @@ build:linux:x86-64:nvhpc-26.1:default:
     EIGEN_CI_CXX_COMPILER: nvc++
     EIGEN_CI_INSTALL: ""
     EIGEN_CI_CROSS_INSTALL: ""
+    # NVHPC's compiler frontend is very memory-hungry with template-heavy code.
+    # Limit parallelism to avoid OOM kills from the kernel.
+    EIGEN_CI_BUILD_JOBS: "8"
 
 ######## CUDA ##################################################################
 
diff --git a/ci/scripts/build.linux.script.sh b/ci/scripts/build.linux.script.sh
index d00edbfda..38e43ab94 100755
--- a/ci/scripts/build.linux.script.sh
+++ b/ci/scripts/build.linux.script.sh
@@ -23,7 +23,13 @@ fi
 # out of resources.  In that case, keep trying to build the remaining
 # targets (k0), then try to build again with a single thread (j1) to minimize
 # resource use.
-cmake --build . ${target} -- -k0 || cmake --build . ${target} -- -k0 -j1
+# EIGEN_CI_BUILD_JOBS can be set to limit parallelism for memory-hungry
+# compilers (e.g. NVHPC).
+jobs=""
+if [[ -n "${EIGEN_CI_BUILD_JOBS}" ]]; then
+  jobs="-j${EIGEN_CI_BUILD_JOBS}"
+fi
+cmake --build . ${target} -- -k0 ${jobs} || cmake --build . ${target} -- -k0 -j1
 
 # Return to root directory.
 cd ${rootdir}