Add --deps-only flag to separate dependency fetching from source builds

This allows CI to fetch and build dependencies (FFTW, HDF5, etc.) on
login nodes with internet access, then build MFC source code on compute
nodes that may have no network connectivity.

Key changes:
- New --deps-only CLI flag for ./mfc.sh build
- Already-configured dependencies are skipped entirely during regular
  builds, guaranteeing no network access in the source build step
- Frontier and Frontier AMD now follow the pattern: deps on login node,
  source build + test on compute node

Author: sbryngelson

.github/workflows/bench.yml

@@ -68,23 +68,23 @@ jobs:
             flag: f
             device: gpu
             interface: acc
-            build_script: "bash .github/workflows/frontier/build.sh gpu acc bench"
+            build_script: "bash .github/workflows/frontier/build.sh gpu acc"
           - cluster: frontier
             name: Oak Ridge | Frontier (CCE)
             group: phoenix
             labels: frontier
             flag: f
             device: gpu
             interface: omp
-            build_script: "bash .github/workflows/frontier/build.sh gpu omp bench"
+            build_script: "bash .github/workflows/frontier/build.sh gpu omp"
           - cluster: frontier_amd
             name: Oak Ridge | Frontier (AMD)
             group: phoenix
             labels: frontier
             flag: famd
             device: gpu
             interface: omp
-            build_script: "bash .github/workflows/frontier_amd/build.sh gpu omp bench"
+            build_script: "bash .github/workflows/frontier_amd/build.sh gpu omp"
     continue-on-error: ${{ matrix.cluster == 'frontier' || matrix.cluster == 'frontier_amd' }}
     runs-on:
       group: ${{ matrix.group }}
@@ -103,7 +103,7 @@ jobs:
           ref: master
           path: master
 
-      - name: Setup & Build
+      - name: Fetch Dependencies
         if: matrix.build_script != ''
         timeout-minutes: 150
         run: |

.github/workflows/common/bench.sh

@@ -21,18 +21,18 @@ if [ "$job_cluster" = "phoenix" ]; then
     trap 'rm -rf "$currentdir" || true' EXIT
 fi
 
-# --- Build (if not pre-built on login node) ---
-# Phoenix builds inside SLURM; Frontier pre-builds via build.sh on the login node.
+# --- Build ---
+# Phoenix builds everything inside SLURM (no login-node build step).
+# Frontier/Frontier AMD: deps already fetched on login node via --deps-only;
+# source code is built here on the compute node.
 # Phoenix: always nuke stale builds (heterogeneous compute nodes → ISA mismatch risk).
 if [ "$job_cluster" = "phoenix" ]; then
     source .github/scripts/clean-build.sh
     clean_build
 fi
 
-if [ ! -d "build" ]; then
-    source .github/scripts/retry-build.sh
-    retry_build ./mfc.sh build -j $n_jobs $build_opts || exit 1
-fi
+source .github/scripts/retry-build.sh
+retry_build ./mfc.sh build -j $n_jobs $build_opts || exit 1
 
 # --- Bench cluster flag ---
 if [ "$job_cluster" = "phoenix" ]; then

.github/workflows/common/test.sh

@@ -21,29 +21,29 @@ if [ "$job_cluster" = "phoenix" ]; then
     trap 'rm -rf "$currentdir" || true' EXIT
 fi
 
-# --- Build (if not pre-built on login node) ---
-# Phoenix builds inside SLURM; Frontier pre-builds via build.sh on the login node.
-# Phoenix builds inside SLURM on heterogeneous compute nodes — always start fresh
-# to avoid SIGILL from stale binaries compiled on a different microarchitecture.
+# --- Build ---
+# Phoenix builds everything inside SLURM (no login-node build step).
+# Frontier/Frontier AMD: deps already fetched on login node via --deps-only;
+# source code is built here on the compute node.
+# Phoenix: always start fresh to avoid SIGILL from stale binaries compiled
+# on a different microarchitecture.
 if [ "$job_cluster" = "phoenix" ]; then
     source .github/scripts/clean-build.sh
     clean_build
 fi
 
-if [ ! -d "build" ]; then
-    source .github/scripts/retry-build.sh
+source .github/scripts/retry-build.sh
 
-    # Phoenix: smoke-test the syscheck binary to catch architecture mismatches
-    # (SIGILL from binaries compiled on a different compute node).
-    validate_cmd=""
-    if [ "$job_cluster" = "phoenix" ]; then
-        validate_cmd='syscheck_bin=$(find build/install -name syscheck -type f 2>/dev/null | head -1); [ -z "$syscheck_bin" ] || "$syscheck_bin" > /dev/null 2>&1'
-    fi
-
-    RETRY_VALIDATE_CMD="$validate_cmd" \
-        retry_build ./mfc.sh test -v --dry-run -j 8 $build_opts || exit 1
+# Phoenix: smoke-test the syscheck binary to catch architecture mismatches
+# (SIGILL from binaries compiled on a different compute node).
+validate_cmd=""
+if [ "$job_cluster" = "phoenix" ]; then
+    validate_cmd='syscheck_bin=$(find build/install -name syscheck -type f 2>/dev/null | head -1); [ -z "$syscheck_bin" ] || "$syscheck_bin" > /dev/null 2>&1'
 fi
 
+RETRY_VALIDATE_CMD="$validate_cmd" \
+    retry_build ./mfc.sh test -v --dry-run -j 8 $build_opts || exit 1
+
 # --- GPU detection and thread count ---
 device_opts=""
 rdma_opts=""

.github/workflows/frontier/build.sh

@@ -14,7 +14,6 @@ esac
 
 job_device=$1
 job_interface=$2
-run_bench=$3
 source .github/scripts/gpu-opts.sh
 build_opts="$gpu_opts"
 
@@ -24,8 +23,4 @@ source .github/scripts/clean-build.sh
 clean_build
 
 source .github/scripts/retry-build.sh
-if [ "$run_bench" == "bench" ]; then
-    retry_build ./mfc.sh build -j 8 $build_opts || exit 1
-else
-    retry_build ./mfc.sh test -v -a --dry-run $([ "$cluster_name" = "frontier" ] && echo "--rdma-mpi") -j 8 $build_opts || exit 1
-fi
+retry_build ./mfc.sh build --deps-only -j 8 $build_opts || exit 1

.github/workflows/test.yml

@@ -400,12 +400,12 @@ jobs:
             echo "Coverage cache: none available — full test suite will run"
           fi
 
-      - name: Build (login node)
+      - name: Fetch Dependencies
         if:   matrix.cluster != 'phoenix'
         timeout-minutes: 60
         run:  bash .github/workflows/${{ matrix.cluster }}/build.sh ${{ matrix.device }} ${{ matrix.interface }}
 
-      - name: Test
+      - name: Build & Test
         run:  bash .github/scripts/submit-slurm-job.sh .github/workflows/common/test.sh ${{ matrix.device }} ${{ matrix.interface }} ${{ matrix.cluster }} ${{ matrix.shard }}
 
       - name: Cancel SLURM Jobs

toolchain/mfc/build.py

@@ -552,6 +552,12 @@ def __build_target(target: typing.Union[MFCTarget, str], case: input.MFCInputFil
 
     history.add(target.name)
 
+    # Dependencies are pinned to fixed versions. If already configured
+    # (built & installed by a prior --deps-only step), skip entirely
+    # to avoid re-entering the superbuild (which may access the network).
+    if target.isDependency and target.is_configured(case):
+        return
+
     for dep in target.requires.compute():
         # If we have already built and installed this target,
         # do not do so again. This can be inferred by whether
@@ -594,6 +600,26 @@ def build(targets=None, case: input.MFCInputFile = None, history: typing.Set[str
     case = case or input.load(ARG("input"), ARG("--"), {})
     case.validate_params()
 
+    if ARG("deps_only", False):
+        all_deps = set()
+        for t in targets:
+            resolved = get_target(t)
+            for dep in resolved.requires.compute():
+                all_deps.add(dep)
+
+        if len(history) == 0:
+            cons.print(f"[bold]Fetch Dependencies | {format_list_to_string([d.name for d in all_deps], 'magenta', 'None')}[/bold]")
+            cons.print(no_indent=True)
+
+        if not all_deps:
+            cons.print("[yellow]No dependencies to build for the requested targets.[/yellow]")
+            return
+
+        for dep in all_deps:
+            __build_target(dep, case, history)
+
+        return
+
     if len(history) == 0:
         cons.print(__generate_header(case, targets))
         cons.print(no_indent=True)

toolchain/mfc/cli/commands.py

@@ -134,6 +134,13 @@
             default=False,
             dest="case_optimization",
         ),
+        Argument(
+            name="deps-only",
+            help="Only fetch and build dependencies, do not build MFC targets.",
+            action=ArgAction.STORE_TRUE,
+            default=False,
+            dest="deps_only",
+        ),
     ],
     examples=[
         Example("./mfc.sh build", "Build all default targets (CPU)"),