Add tests for lammps_gather() and lammps_scatter()

unittest/c-library/test_library_mpi.cpp

@@ -115,3 +115,131 @@ TEST(MPI, sub_box)
     lammps_close(lmp);
     ::testing::internal::GetCapturedStdout();
 };
+
+class MPITest : public ::testing::Test {
+public:
+    void command(const std::string &line) {
+        lammps_command(lmp, line.c_str());
+    }
+
+protected:
+    const char * testbinary = "LAMMPSTest";
+    void *lmp;
+
+    void SetUp() override
+    {
+        const char *args[] = { testbinary, "-log", "none", "-echo", "screen", "-nocite"};
+        char **argv = (char **)args;
+        int argc    = sizeof(args) / sizeof(char *);
+        if (!verbose) ::testing::internal::CaptureStdout();
+        lmp = lammps_open(argc, argv, MPI_COMM_WORLD, nullptr);
+        InitSystem();
+        if (!verbose) ::testing::internal::GetCapturedStdout();
+    }
+
+    virtual void InitSystem() {
+        command("units           lj");
+        command("atom_style      atomic");
+        command("atom_modify     map yes");
+
+        command("lattice         fcc 0.8442");
+        command("region          box block 0 2 0 2 0 2");
+        command("create_box      1 box");
+        command("create_atoms    1 box");
+        command("mass            1 1.0");
+
+        command("velocity        all create 3.0 87287");
+
+        command("pair_style      lj/cut 2.5");
+        command("pair_coeff      1 1 1.0 1.0 2.5");
+
+        command("neighbor        0.3 bin");
+        command("neigh_modify    every 20 delay 0 check no");
+    }
+
+    void TearDown() override
+    {
+        if (!verbose) ::testing::internal::CaptureStdout();
+        lammps_close(lmp);
+        lmp = nullptr;
+        if (!verbose) ::testing::internal::GetCapturedStdout();
+    }
+};
+
+#if !defined(LAMMPS_BIGBIG)
+
+TEST_F(MPITest, gather) {
+    int64_t natoms = (int64_t)lammps_get_natoms(lmp);
+    ASSERT_EQ(natoms, 32);
+    int * p_nlocal = (int*)lammps_extract_global(lmp, "nlocal");
+    int nlocal = *p_nlocal;
+    EXPECT_LT(nlocal, 32);
+    EXPECT_EQ(nlocal, 8);
+
+    // get the entire x on all procs
+    double * x = new double[natoms * 3];
+    lammps_gather(lmp, (char*)"x", 1, 3, x);
+
+    int * tag = (int*)lammps_extract_atom(lmp, "id");
+    double ** x_local = (double**)lammps_extract_atom(lmp, "x");
+
+    // each proc checks its local atoms
+    for(int i = 0; i < nlocal; i++) {
+        int64_t j = tag[i]-1;
+        double * x_i = x_local[i];
+        double * x_g = &x[j*3];
+        EXPECT_DOUBLE_EQ(x_g[0], x_i[0]);
+        EXPECT_DOUBLE_EQ(x_g[1], x_i[1]);
+        EXPECT_DOUBLE_EQ(x_g[2], x_i[2]);
+    }
+
+    delete [] x;
+}
+
+TEST_F(MPITest, scatter) {
+    int * p_nlocal = (int*)lammps_extract_global(lmp, "nlocal");
+    int nlocal = *p_nlocal;
+    double * x_orig = new double[3*nlocal];
+    double ** x_local = (double**)lammps_extract_atom(lmp, "x");
+
+    // make copy of original local x vector
+    for(int i = 0; i < nlocal; i++) {
+        int j = 3*i;
+        x_orig[j] = x_local[i][0];
+        x_orig[j + 1] = x_local[i][1];
+        x_orig[j + 2] = x_local[i][2];
+    }
+
+    // get the entire x on all procs
+    int64_t natoms = (int64_t)lammps_get_natoms(lmp);
+    double * x = new double[natoms * 3];
+    lammps_gather(lmp, (char*)"x", 1, 3, x);
+
+    // shift all coordinates by 0.001
+    const double delta = 0.001;
+    for(int64_t i = 0; i < 3*natoms; i++) x[i] += delta;
+
+    // update positions of all atoms
+    lammps_scatter(lmp, (char*)"x", 1, 3, x);
+    delete [] x;
+    x = nullptr;
+
+    // get new nlocal and x_local
+    p_nlocal = (int*)lammps_extract_global(lmp, "nlocal");
+    nlocal = *p_nlocal;
+    x_local = (double**)lammps_extract_atom(lmp, "x");
+
+    ASSERT_EQ(nlocal, 8);
+
+    // each proc checks its local atoms for shift
+    for(int i = 0; i < nlocal; i++) {
+        double * x_a = x_local[i];
+        double * x_b = &x_orig[i*3];
+        EXPECT_DOUBLE_EQ(x_a[0], x_b[0]+delta);
+        EXPECT_DOUBLE_EQ(x_a[1], x_b[1]+delta);
+        EXPECT_DOUBLE_EQ(x_a[2], x_b[2]+delta);
+    }
+
+    delete [] x_orig;
+}
+#endif