Support variable substitutions in variable definitions

run-exp.py

@@ -241,11 +241,24 @@ def main(config_file, global_timeout, dry_run):
     print(f">     and {c.repetitions} repetitions")
     print()
 
-    variable_map = {v.name: v.evaluate({}) for v in c.variables}
-    value_combinations = itertools.product(*variable_map.values())
-    run_values = [dict(zip(variable_map.keys(), vals)) for vals in value_combinations]
+    # we precompute all variable values to be able to abort early in case of a problem,
+    # for instance, if a file does not exist
+    variable_maps = [{}]
 
-    for variables in run_values:
+    for variable in c.variables:
+        updated_variable_maps = []
+
+        for variable_map in variable_maps:
+            values = variable.evaluate(variable_map)
+
+            for value in values:
+                updated_map = variable_map.copy()
+                updated_map[variable.name] = value
+                updated_variable_maps.append(updated_map)
+
+        variable_maps = updated_variable_maps
+
+    for variables in variable_maps:
         print()
         print("Running tasks with variable map: ")
         print(variables)