We have to also dump empty models, for implementations which aren't calibrated yet

src/core/perfmodel/perfmodel_history.c

@@ -335,8 +335,6 @@ static void dump_per_arch_model_file(FILE *f, struct starpu_perfmodel *model, un
 		}
 	}
 
-	if (nentries == 0)
-		return;
 	/* header */
 	char archname[32];
 	starpu_perfmodel_get_arch_name((enum starpu_perf_archtype) arch, archname, 32, nimpl);