Add an example for the named paramter namespace.

examples/usage/allgatherv_example.cpp

@@ -38,61 +38,81 @@ int main() {
     // Note, that the size of the input vector is different for each rank.
     std::vector<int> input(comm.rank(), comm.rank_signed());
 
-    { // Basic use case; gather the inputs across all ranks to all ranks.
+    {
+        // we are including the namespace here to reduce verbosity
+        using namespace kamping;
+        { // Basic use case; gather the inputs across all ranks to all ranks.
+            auto const output = comm.allgatherv(send_buf(input));
+            print_result_on_root(output, comm);
+        }
+
+        { // We can also request the number of elements received from each rank. The recv_buf will always be the first
+          // out parameter. After that, the output parameters are ordered as they appear in the function call. KaMPIng
+          // calls like allgatherv return a result object which can be decomposed using structured bindings (here) or
+          // explicit extract_*() calls (see below).
+            auto [recv_buffer, recv_counts] = comm.allgatherv(send_buf(input), recv_counts_out());
+        }
+
+        { // To re-use memory, we can provide an already allocated container to the MPI call.
+            std::vector<int> output;
+            // Let KaMPIng resize the recv_buffer to the correct size. Other possibilities are no_resize and grow_only.
+            comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output));
+
+            // We can also re-use already allocated containers for the other output parameters, e.g. recv_counts.
+            std::vector<int> output_counts(comm.size());
+            std::iota(output_counts.begin(), output_counts.end(), 0);
+            comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output), recv_counts(output_counts));
+
+            std::vector<int> displacements(comm.size());
+            std::exclusive_scan(output_counts.begin(), output_counts.end(), displacements.begin(), 0);
+            output.clear();
+
+            // In this example, we combine all of the concepts mentioned above:
+            // - Use input as the send buffer
+            // - Receive all elements into recv_buffer, resizing it to fit exactly the number of elements received.
+            // - Output the number of elements received from each rank into recv_counts.
+            // - Output the displacement of the first element received from each rank into recv_displs.
+            comm.allgatherv(
+                send_buf(input),
+                recv_buf<resize_to_fit>(output),
+                recv_counts(output_counts),
+                recv_displs(displacements)
+            );
+        }
+
+        { // It is also possible to use result.extract_*() calls instead of decomposing the result object using
+          // structured bindings in order to increase readability.
+            auto       result      = comm.allgatherv(send_buf(input), recv_counts_out(), recv_displs_out());
+            auto const recv_buffer = result.extract_recv_buffer();
+            auto const recv_counts = result.extract_recv_counts();
+            auto const recv_displs = result.extract_recv_displs();
+        }
+
+        { // C++ views can be used to send parts of the data.
+            input.resize(comm.rank() + 1, comm.rank_signed());
+
+            // Note, if you're on C++ >= 20 you can use std::span instead.
+            comm.allgatherv(send_buf(kamping::Span(input).subspan(0, comm.rank())));
+
+            // Alternatively
+            comm.allgatherv(send_buf(input), send_count(comm.rank_signed()));
+
+            // let's restore the input
+            input.resize(comm.rank());
+        }
+    }
+    {
+        // if you don't want to polute your global namespace with all KaMPIng's symbols, you can just use the namespace
+        // for named parameters
+        using namespace kamping::params;
         auto const output = comm.allgatherv(send_buf(input));
         print_result_on_root(output, comm);
     }
-
-    { // We can also request the number of elements received from each rank. The recv_buf will always be the first out
-      // parameter. After that, the output parameters are ordered as they appear in the function call.
-      // KaMPIng calls like allgatherv return a result object which can be decomposed using structured
-      // bindings (here) or explicit extract_*() calls (see below).
-        auto [recv_buffer, recv_counts] = comm.allgatherv(send_buf(input), recv_counts_out());
-    }
-
-    { // To re-use memory, we can provide an already allocated container to the MPI call.
-        std::vector<int> output;
-        // Let KaMPIng resize the recv_buffer to the correct size. Other possibilities are no_resize and grow_only.
-        comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output));
-
-        // We can also re-use already allocated containers for the other output parameters, e.g. recv_counts.
-        std::vector<int> output_counts(comm.size());
-        std::iota(output_counts.begin(), output_counts.end(), 0);
-        comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output), recv_counts(output_counts));
-
-        std::vector<int> displacements(comm.size());
-        std::exclusive_scan(output_counts.begin(), output_counts.end(), displacements.begin(), 0);
-        output.clear();
-
-        // In this example, we combine all of the concepts mentioned above:
-        // - Use input as the send buffer
-        // - Receive all elements into recv_buffer, resizing it to fit exactly the number of elements received.
-        // - Output the number of elements received from each rank into recv_counts.
-        // - Output the displacement of the first element received from each rank into recv_displs.
-        comm.allgatherv(
-            send_buf(input),
-            recv_buf<resize_to_fit>(output),
-            recv_counts(output_counts),
-            recv_displs(displacements)
-        );
-    }
-
-    { // It is also possible to use result.extract_*() calls instead of decomposing the result object using structured
-      // bindings in order to increase readability.
-        auto       result      = comm.allgatherv(send_buf(input), recv_counts_out(), recv_displs_out());
-        auto const recv_buffer = result.extract_recv_buffer();
-        auto const recv_counts = result.extract_recv_counts();
-        auto const recv_displs = result.extract_recv_displs();
-    }
-
-    { // C++ views can be used to send parts of the data.
-        input.resize(comm.rank() + 1, comm.rank_signed());
-
-        // Note, if you're on C++ >= 20 you can use std::span instead.
-        comm.allgatherv(send_buf(kamping::Span(input).subspan(0, comm.rank())));
-
-        // Alternatively
-        comm.allgatherv(send_buf(input), send_count(comm.rank_signed()));
+    {
+        // you can also use define a shorthand for the named parameter namespace, to reduce code verbosity
+        namespace kmp     = kamping::params;
+        auto const output = comm.allgatherv(kmp::send_buf(input));
+        print_result_on_root(output, comm);
     }
 
     return 0;