From 1ad1972a5e741460eabe425ecae57e16e54190ab Mon Sep 17 00:00:00 2001
From: Carl Pearson <cwpears@sandia.gov>
Date: Fri, 30 Apr 2021 14:53:17 -0600
Subject: [PATCH] add one-sided

---
 one_sided.cpp | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 one_sided.cpp

diff --git a/one_sided.cpp b/one_sided.cpp
new file mode 100644
index 0000000..5cf47ef
--- /dev/null
+++ b/one_sided.cpp
@@ -0,0 +1,55 @@
+#include <mpi.h>
+#include <iostream>
+
+int main(int argc, char **argv) {
+
+  MPI_Init(&argc, &argv);
+
+
+  MPI_Win win;
+  int *a;
+  {
+  /* Make rank accessible in all processes */
+
+    MPI_Aint size = sizeof(int);
+    int disp_unit = sizeof(int);
+    MPI_Win_allocate(size, disp_unit, MPI_INFO_NULL, MPI_COMM_WORLD, &a, &win);
+  }
+
+  int rank, size;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+  // expect our a to be set by the left
+  int source;
+  if (0 == rank) {
+    source = size - 1;
+  } else {
+    source = rank - 1;
+  }
+
+  int target; // set the right
+  if (rank == size - 1) {
+    target = 0;
+  } else {
+    target = rank + 1;
+  }
+
+  // send our rank to the target window
+  std::cout << "rank " << rank << " put to " << target << std::endl << std::flush;
+  MPI_Put(&rank, 1, MPI_INT, target, 0, 1, MPI_INT, win);   
+
+  MPI_Barrier(MPI_COMM_WORLD);
+
+  int err = 0;
+
+  if (*a != source) {
+    std::cerr << "ERR: rank " << rank << " got " << *a << " expected " << source << std::endl;
+    err = 1;
+  }               
+
+  MPI_Win_free(&win);
+  MPI_Finalize();
+  std::cout << "rank " << rank << "completed" << std::endl << std::flush;
+  return err;
+}