hpcg: refactor ss and gen using a common file

- The file gen.nix now provides an experiment for each unit, to reduce
  the evaluation time.

- The pipeline is specified in the common.nix file only.

- The input dataset path is no longer symlinked, but is specified in the
  "--load" argument.

- The size is renamed to "sizePerTask" instead of "n".

garlic/exp/hpcg/common.nix

@@ -0,0 +1,72 @@
+{
+  stdenv
+, stdexp
+, bsc
+, stages
+, callPackage
+}:
+
+with stdenv.lib;
+
+rec {
+
+  checkInput = {nextStage, conf, ...}: stages.exec {
+    inherit nextStage;
+    pre = optionalString (! (conf.enableGen or false)) (
+    let
+      gen = callPackage ./gen.nix { };
+      inputTre = gen.getInputTre conf;
+      exp = inputTre.experiment;
+      unit = elemAt exp.units 0;
+      expName = baseNameOf (toString exp);
+      unitName = baseNameOf (toString unit);
+      inputPath = "$GARLIC_OUT/${expName}/${unitName}/1";
+    in
+      ''
+        # Force the generation of the input resultTree as a dependency:
+        # ${toString inputTre.result}
+
+        # Ensure the input dataset is still available
+        export HPCG_INPUT_PATH="${toString inputPath}"
+
+        if [ ! -e "$HPCG_INPUT_PATH" ]; then
+          >&2 echo "Missing input dataset: $HPCG_INPUT_PATH"
+          exit 1
+        fi
+      ''
+    );
+  };
+
+  getSizePerTask = cpusPerTask: sizePerCpu:
+    mapAttrs (name: val: val * cpusPerTask) sizePerCpu;
+
+  exec = {nextStage, conf, ...}: let
+    actionArg = if (conf.enableGen or false)
+    then "--store=."
+    else "--load=\"$HPCG_INPUT_PATH\"";
+
+  in stages.exec {
+    inherit nextStage;
+    argv = [
+      "--nx=${toString conf.sizePerTask.x}"
+      "--ny=${toString conf.sizePerTask.y}"
+      "--nz=${toString conf.sizePerTask.z}"
+      "--npx=${toString conf.nprocs.x}"
+      "--npy=${toString conf.nprocs.y}"
+      "--npz=${toString conf.nprocs.z}"
+      "--nblocks=${toString conf.nblocks}"
+      "--ncomms=${toString conf.ncomms}"
+      # The input symlink is generated by the input stage, which is generated by
+      # the genInput function.
+      actionArg
+    ] ++ optional (conf.disableAspectRatio or false) "--no-ar=1";
+  };
+
+  program = {nextStage, conf, ...}: bsc.apps.hpcg.override {
+    inherit (conf) gitBranch;
+  };
+
+  pipeline = stdexp.stdPipeline ++ [
+    checkInput
+    exec program ];
+}