diff --git a/test/test_group_data.cpp b/test/test_group_data.cpp
index e5c1d0069..676d45e27 100644
--- a/test/test_group_data.cpp
+++ b/test/test_group_data.cpp
@@ -44,17 +44,29 @@ int main(int argc, char *argv[]) {
   ParallelGroupBuilder<unsigned> builder(&rptr, &data);
   builder.InitBudget(0, nthread);
 
-  bst_omp_uint nlen = raw.size();
-  #pragma omp parallel for schedule(static)
-  for (bst_omp_uint i = 0; i < nlen; ++i) {
-    builder.AddBudget(raw[i].first, omp_get_thread_num());
+  size_t nstep = (raw.size() +nthread-1)/ nthread;
+  #pragma omp parallel
+  {
+    int tid = omp_get_thread_num(); 
+    size_t begin = tid * nstep;
+    size_t end = std::min((tid + 1) * nstep, raw.size());
+    for (size_t i = begin; i < end; ++i) {
+      builder.AddBudget(raw[i].first, tid);
+    }
   }
   double first_cost = time(NULL) - start_t;
   builder.InitStorage();  
-  #pragma omp parallel for schedule(static)
-  for (bst_omp_uint i = 0; i < nlen; ++i) {
-    builder.Push(raw[i].first, raw[i].second, omp_get_thread_num());
-  }  
+
+  #pragma omp parallel
+  {
+    int tid = omp_get_thread_num(); 
+    size_t begin = tid * nstep;
+    size_t end = std::min((tid + 1)* nstep, raw.size());
+    for (size_t i = begin; i < end; ++i) {
+      builder.Push(raw[i].first, raw[i].second, tid);
+    }
+  }
+
   double second_cost = time(NULL) - start_t;
   printf("all finish, phase1=%g sec, phase2=%g sec\n", first_cost, second_cost);
   Check(rptr.size() <= nkey+1, "nkey exceed bound");