diff --git a/Makefile b/Makefile
index d9603f4..728522f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 # Supported: GCC, CLANG, ICC
-TAG = GCC
+TAG ?= GCC
 
 #CONFIGURE BUILD SYSTEM
 TARGET	   = bwbench-$(TAG)
diff --git a/src/sum.c b/src/sum.c
index 6a6698e..b31074b 100644
--- a/src/sum.c
+++ b/src/sum.c
@@ -36,7 +36,7 @@ double sum(
     double sum = 0.0;
 
     S = getTimeStamp();
-#pragma omp parallel for
+#pragma omp parallel for simd reduction(+:sum) 
     for (int i=0; i<N; i++) {
         sum += a[i];
     }