diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index fcedccb4..b49b05fe 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,6 +1,9 @@
 name: CI
 
-on: [push]
+on:
+  push:
+  schedule:
+    - cron: '0 0 1,15 * *' # JST 9:00 on 1st and 15th every month
 
 jobs:
   ctest:
@@ -8,11 +11,17 @@ jobs:
 
     strategy:
       matrix:
-        os: ["ubuntu-22.04", "macos-11", "ubuntu-20.04"]
+        os: ["ubuntu-22.04", "ubuntu-20.04", "macos-latest"]
+        ompsize: [1, 4]
+        exclude:
+          - os: "macos-latest"
+            ompsize: 4 # OMP on macOS is too slow
       fail-fast: false
+    env:
+      OMP_NUM_THREADS: ${{ matrix.ompsize }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: apt
         if: ${{ runner.os == 'Linux' }}
@@ -25,9 +34,13 @@ jobs:
         run: |
           brew install openmpi scalapack libomp
 
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
       - name: pip
         run: |
-          python -m pip install numpy
           python3 -m pip install numpy
 
       - name: make workspace
@@ -40,10 +53,12 @@ jobs:
           if [ ${{ runner.os }} = "macOS" ] ; then
             # CONFIG=apple requires gfortran but macOS runner has not, but gfortran-11, 12, ...
             ln -s `which gfortran-11` gfortran
-            env PATH=`pwd`:$PATH HOMEBREW_PREFIX=/usr/local cmake -DCONFIG=apple -DCMAKE_VERBOSE_MAKEFILE=ON $GITHUB_WORKSPACE
+            env PATH=`pwd`:$PATH cmake -DCONFIG=apple -DCMAKE_VERBOSE_MAKEFILE=ON $GITHUB_WORKSPACE
           else
             cmake -DCMAKE_VERBOSE_MAKEFILE=ON $GITHUB_WORKSPACE
           fi
+        env:
+          HOMEBREW_PREFIX: /opt/homebrew
 
       - name: build
         working-directory: ${{runner.workspace}}/build