Fix #858: tell buildx which platform to build for

.github/workflows/ci_docker_tests.yaml

@@ -65,8 +65,19 @@
           fetch-depth: 1
           submodules: recursive
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+        with:
+          driver: docker
+
       - name: Build Docker images
-        run: docker compose build
+        run: |
+          # Running locally, a plain "docker compose build" works as expected.
+          # On GitHub, buildx tries to build all 3 images in parallel even if
+          # you use env var COMPOSE_PARALLEL_LIMIT or option --parallel 1.
+          # The build then fails because the qsim-base image is not available
+          # to the other two build processes.
+          docker compose --parallel 1 build
 
       - name: Run C++ tests
         run: docker run --rm qsim-cxx-tests:latest
@@ -75,7 +86,7 @@
         run: docker run --rm qsim-py-tests:latest
 
       - name: Run a sample simulation
-        run: docker run --rm qsim:latest -c /qsim/circuits/circuit_q24
+        run: docker run --rm qsim-base:latest -c /qsim/circuits/circuit_q24
 
       - name: Test installation process
         run: |

Dockerfile

@@ -1,5 +1,5 @@
 # Base OS
-FROM ubuntu:24.04
+FROM ubuntu:24.04 AS qsim-base
 
 # Allow passing this variable in from the outside.
 ARG CUDA_PATH

docker-compose.yml

@@ -1,23 +1,26 @@
 services:
-    qsim:
-        image: qsim
-        container_name: qsim
+    qsim-base-image:
+        image: qsim-base
+        platform: linux/amd64
         build:
             context: ./
             dockerfile: Dockerfile
-    qsim-cxx-tests:
+            target: qsim-base
+
+    qsim-cxx-tests-image:
         image: qsim-cxx-tests
-        container_name: qsim-cxx-tests
         build:
             context: ./
             dockerfile: tests/Dockerfile
+            target: qsim-cxx-tests
         depends_on:
-        - qsim
-    qsim-py-tests:
+          - qsim-base-image
+
+    qsim-py-tests-image:
         image: qsim-py-tests
-        container_name: qsim-py-tests
         build:
             context: ./
             dockerfile: pybind_interface/Dockerfile
+            target: qsim-py-tests
         depends_on:
-        - qsim
+          - qsim-base-image

pybind_interface/Dockerfile

@@ -1,5 +1,5 @@
 # Base OS
-FROM qsim
+FROM qsim-base AS qsim-py-tests
 
 # Copy relevant files
 COPY ./pybind_interface/ /qsim/pybind_interface/

tests/Dockerfile

@@ -1,5 +1,5 @@
 # Base OS
-FROM qsim
+FROM qsim-base AS qsim-cxx-tests
 
 # Copy relevant files
 COPY ./tests/ /qsim/tests/