Tests: supplementing some tests with OPENMP check directives (#5504)

* Tests: supplementing some tests with OPENMP check directives to successfully compile when OpenMP is not enabled

* Correct __OPENMP macro spell

* Revert "Correct __OPENMP macro spell"

This reverts commit 7728162.

* Update elecstate test to remove commands of omp macro definition

* Correct __OPENMP macro spell of #include

source/module_base/module_mixing/test/mixing_test.cpp

@@ -1,4 +1,6 @@
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 #include "../broyden_mixing.h"
 #include "../plain_mixing.h"
@@ -151,7 +153,9 @@ class Mixing_Test : public testing::Test
 
 TEST_F(Mixing_Test, BroydenSolveLinearEq)
 {
+#ifdef _OPENMP
     omp_set_num_threads(1);
+#endif
     init_method("broyden");
     std::vector<double> x_in = xd_ref;
     std::vector<double> x_out(3);
@@ -196,7 +200,9 @@ TEST_F(Mixing_Test, BroydenSolveLinearEq)
 
 TEST_F(Mixing_Test, PulaySolveLinearEq)
 {
+#ifdef _OPENMP
     omp_set_num_threads(1);
+#endif
     init_method("pulay");
     std::vector<double> x_in = xd_ref;
     std::vector<double> x_out(3);
@@ -242,7 +248,9 @@ TEST_F(Mixing_Test, PulaySolveLinearEq)
 
 TEST_F(Mixing_Test, PlainSolveLinearEq)
 {
+#ifdef _OPENMP
     omp_set_num_threads(1);
+#endif
     init_method("plain");
     std::vector<double> x_in = xd_ref;
     std::vector<double> x_out(3);

source/module_elecstate/test/charge_mixing_test.cpp

@@ -10,7 +10,10 @@
 #include "module_basis/module_pw/pw_basis.h"
 #include "module_hamilt_general/module_xc/xc_functional.h"
 #undef private
+
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 int FUNC_TYPE = 1;
 
@@ -116,7 +119,9 @@ class ChargeMixingTest : public ::testing::Test
 
 TEST_F(ChargeMixingTest, SetMixingTest)
 {
+#ifdef _OPENMP
     omp_set_num_threads(1);
+#endif
     PARAM.input.nspin = 1;
     Charge_Mixing CMtest;
     CMtest.set_rhopw(&pw_basis, &pw_basis);
@@ -214,7 +219,9 @@ TEST_F(ChargeMixingTest, SetMixingTest)
 
 TEST_F(ChargeMixingTest, InitMixingTest)
 {
+#ifdef _OPENMP
     omp_set_num_threads(1);
+#endif
     PARAM.input.nspin = 1;
     FUNC_TYPE = 1;
     Charge_Mixing CMtest;