From 72643ee400130c35a0e662560ee09a479a913333 Mon Sep 17 00:00:00 2001
From: Dmitriy Morozov <dmitriy@mrzv.org>
Date: Wed, 20 Dec 2023 09:54:02 -0800
Subject: [PATCH] Add mpi::communicator::ssend()

---
 include/diy/mpi/communicator.hpp   |  3 +++
 include/diy/mpi/point-to-point.cpp | 10 ++++++++++
 include/diy/mpi/point-to-point.hpp |  8 ++++++++
 3 files changed, 21 insertions(+)

diff --git a/include/diy/mpi/communicator.hpp b/include/diy/mpi/communicator.hpp
index 317e7d095..a4facaa14 100644
--- a/include/diy/mpi/communicator.hpp
+++ b/include/diy/mpi/communicator.hpp
@@ -62,6 +62,9 @@ namespace mpi
       template<class T>
       void      send(int dest, int tag, const T& x) const   { detail::send(comm_, dest, tag, x); }
 
+      template<class T>
+      void      ssend(int dest, int tag, const T& x) const   { detail::ssend(comm_, dest, tag, x); }
+
       //! Receive `x` from `dest` using `tag` (blocking).
       //! If `T` is an `std::vector<...>`, `recv` will resize it to fit exactly the sent number of values.
       template<class T>
diff --git a/include/diy/mpi/point-to-point.cpp b/include/diy/mpi/point-to-point.cpp
index 7696ff4bf..bba84cebe 100644
--- a/include/diy/mpi/point-to-point.cpp
+++ b/include/diy/mpi/point-to-point.cpp
@@ -31,6 +31,16 @@ void send(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, con
 #endif
 }
 
+void ssend(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, const datatype& type)
+{
+#if DIY_HAS_MPI
+  MPI_Ssend(data, count, mpi_cast(type.handle), dest, tag, mpi_cast(comm));
+#else
+  (void) comm; (void) dest; (void) tag; (void) data; (void) count; (void) type;
+  DIY_UNSUPPORTED_MPI_CALL(MPI_Ssend);
+#endif
+}
+
 status probe(DIY_MPI_Comm comm, int source, int tag)
 {
 #if DIY_HAS_MPI
diff --git a/include/diy/mpi/point-to-point.hpp b/include/diy/mpi/point-to-point.hpp
index b0db2d447..150d3c8f0 100644
--- a/include/diy/mpi/point-to-point.hpp
+++ b/include/diy/mpi/point-to-point.hpp
@@ -24,6 +24,7 @@ DIY_MPI_EXPORT extern const int any_tag;
 namespace detail
 {
   DIY_MPI_EXPORT_FUNCTION void send(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, const datatype& type);
+  DIY_MPI_EXPORT_FUNCTION void ssend(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, const datatype& type);
   DIY_MPI_EXPORT_FUNCTION request isend(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, const datatype& type);
   DIY_MPI_EXPORT_FUNCTION request issend(DIY_MPI_Comm comm, int dest, int tag, const void* data, int count, const datatype& type);
   DIY_MPI_EXPORT_FUNCTION status probe(DIY_MPI_Comm comm, int source, int tag);
@@ -37,6 +38,13 @@ namespace detail
     send(comm, dest, tag, address(x), count(x), datatype_of(x));
   }
 
+  template <class T>
+  inline void ssend(DIY_MPI_Comm comm, int dest, int tag, const T& x)
+  {
+    static_assert(std::is_same<typename is_mpi_datatype<T>::type, true_type>::value, "is_mpi_datatype<T>::type must be true_type");
+    ssend(comm, dest, tag, address(x), count(x), datatype_of(x));
+  }
+
   template <class T>
   status recv(DIY_MPI_Comm comm, int source, int tag, T& x)
   {