Add simple MPI tests

- Communicator of the correct size
- Point to point communication works between nodes

ci/templates/test_image.yml.j2

@@ -45,3 +45,26 @@ test_job_test_image_gromacs-{{os}}{{osver}}-spack{{spackver}}-{{archstr[arch]}}:
     {% if arch == "rocm" -%}
     - echo "TODO Lets ignore ROCm for now"
     {%- endif %}
+
+##### mpi_simple
+
+build_job_test_image_mpi_simple-{{os}}{{osver}}-spack{{spackver}}-{{archstr[arch]}}:
+  stage: build_test_image
+  extends:
+    - {{container_builder[arch]}}
+  variables:
+    DOCKERFILE: "test/mpi_simple/Dockerfile.mpi_simple"
+    PERSIST_IMAGE_NAME: "{{registry_path}}/test-mpi_simple:spack{{spackver}}-{{os}}{{osver}}-{{archstr[arch]}}"
+    DOCKER_BUILD_ARGS: '["BUILDIMG={{registry_build_image_name_tag}}", "RUNTIMEIMG={{registry_runtime_image_name_tag}}", "TARGET={{spack_target}}"]'
+    SLURM_JOB_NUM_NODES: 2
+    SLURM_NTASKS: 2
+    SLURM_MPI_TYPE: pmi2
+
+test_job_test_image_mpi_simple-{{os}}{{osver}}-spack{{spackver}}-{{archstr[arch]}}:
+  stage: test_test_image
+  extends:
+    - {{container_runner[arch]}}
+  image: "{{registry_path}}/test-mpi_simple:spack{{spackver}}-{{os}}{{osver}}-{{archstr[arch]}}"
+  script:
+    - hostname
+    - /src/mpi_send_recv

test/mpi_simple/Dockerfile.mpi_simple

@@ -0,0 +1,34 @@
+ARG BUILDIMG
+FROM $BUILDIMG as builder
+
+RUN apt-get update \
+  && env DEBIAN_FRONTEND=noninteractive TZ=Europe/Zurich apt-get -yqq install --no-install-recommends build-essential
+
+ARG TARGET
+RUN spack-install-helper \
+    "$TARGET"
+
+
+# copy only relevant parts to the final container
+ARG RUNTIMEIMG
+FROM $RUNTIMEIMG
+
+# it is important to keep the paths, otherwise your installation is broken
+# all these paths are created with the above `spack-install-helper` invocation
+COPY --from=builder /opt/spack-environment /opt/spack-environment
+COPY --from=builder /opt/software /opt/software
+COPY --from=builder /opt/._view /opt/._view
+COPY --from=builder /etc/profile.d/z10_spack_environment.sh /etc/profile.d/z10_spack_environment.sh
+
+# Some boilerplate to get all paths correctly - fix_spack_install is part of the base image
+# and makes sure that all important things are being correctly setup
+RUN fix_spack_install
+
+RUN apt-get update \
+  && env DEBIAN_FRONTEND=noninteractive TZ=Europe/Zurich apt-get -yqq install --no-install-recommends build-essential
+
+# Finally do what we need
+COPY . /src
+
+RUN cd /src \
+ && mpicc mpi_send_recv.c -o mpi_send_recv

test/mpi_simple/mpi_send_recv.c

@@ -0,0 +1,66 @@
+/****************************************************************
+ *                                                              *
+ * This file has been written as a sample solution to an        *
+ * exercise in a course given at the CSCS Summer School.        *
+ * It is made freely available with the understanding that      *
+ * every copy of this file must include this header and that    *
+ * CSCS take no responsibility for the use of the enclosed      *
+ * teaching material.                                           *
+ *                                                              *
+ * Purpose: A program to try MPI_Comm_size and MPI_Comm_rank.   *
+ *                                                              *
+ * Contents: C-Source                                           *
+ ****************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <mpi.h>
+
+
+int main(int argc, char *argv[])
+{
+    /* declare any variables you need */
+    int rank;
+    int size;
+    int number;
+    MPI_Status status;
+
+    MPI_Init(&argc, &argv);
+
+    /* Get the rank of each process */
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+    /* Get the size of the communicator */
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    /* Write code such that every process writes its rank and the size of the communicator,
+     * but only process 0 prints "hello world*/
+    printf("Process %d out of %d.\n", rank, size);
+
+    /* Check communicator size */
+    if (size != 2) {
+        printf("Error: Proces %d: communicator size %d, expected 2.\n", rank, size);
+        MPI_Finalize();
+        exit(1);
+    }
+
+    /* Check send, receive */
+    if (rank == 0) {
+        number = 42;
+        printf("Process %d: sending number %d\n", rank, number);
+        MPI_Send(&number, 1, MPI_INT, 1, 0, MPI_COMM_WORLD);
+    }
+
+    if (rank == 1) {
+        MPI_Recv(&number, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
+        printf("Process %d: received number %d\n", rank, number);
+        if (number != 42) {
+            printf("Error: Process %d: received %d, expected 42.\n", rank, number);
+            MPI_Finalize();
+            exit(1);
+        }
+    }
+
+    MPI_Finalize();
+    return 0;
+}