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niklas-uhlniklas-uhl
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Move named parameters to separate namespace. (#759)
* Move named paramters to seperate namespace and re-export it to the kamping namespace. * Add an example for the named paramter namespace. * Fix typo.
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-52
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3 files changed

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‎examples/usage/allgatherv_example.cpp

+72-52
Original file line numberDiff line numberDiff line change
@@ -38,61 +38,81 @@ int main() {
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// Note, that the size of the input vector is different for each rank.
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std::vector<int> input(comm.rank(), comm.rank_signed());
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41-
{ // Basic use case; gather the inputs across all ranks to all ranks.
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{
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// we are including the namespace here to reduce verbosity
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using namespace kamping;
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{ // Basic use case; gather the inputs across all ranks to all ranks.
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auto const output = comm.allgatherv(send_buf(input));
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print_result_on_root(output, comm);
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}
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{ // We can also request the number of elements received from each rank. The recv_buf will always be the first
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// out parameter. After that, the output parameters are ordered as they appear in the function call. KaMPIng
51+
// calls like allgatherv return a result object which can be decomposed using structured bindings (here) or
52+
// explicit extract_*() calls (see below).
53+
auto [recv_buffer, recv_counts] = comm.allgatherv(send_buf(input), recv_counts_out());
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}
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{ // To re-use memory, we can provide an already allocated container to the MPI call.
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std::vector<int> output;
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// Let KaMPIng resize the recv_buffer to the correct size. Other possibilities are no_resize and grow_only.
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comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output));
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61+
// We can also re-use already allocated containers for the other output parameters, e.g. recv_counts.
62+
std::vector<int> output_counts(comm.size());
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std::iota(output_counts.begin(), output_counts.end(), 0);
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comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output), recv_counts(output_counts));
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std::vector<int> displacements(comm.size());
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std::exclusive_scan(output_counts.begin(), output_counts.end(), displacements.begin(), 0);
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output.clear();
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70+
// In this example, we combine all of the concepts mentioned above:
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// - Use input as the send buffer
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// - Receive all elements into recv_buffer, resizing it to fit exactly the number of elements received.
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// - Output the number of elements received from each rank into recv_counts.
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// - Output the displacement of the first element received from each rank into recv_displs.
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comm.allgatherv(
76+
send_buf(input),
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recv_buf<resize_to_fit>(output),
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recv_counts(output_counts),
79+
recv_displs(displacements)
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);
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}
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{ // It is also possible to use result.extract_*() calls instead of decomposing the result object using
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// structured bindings in order to increase readability.
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auto result = comm.allgatherv(send_buf(input), recv_counts_out(), recv_displs_out());
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auto const recv_buffer = result.extract_recv_buffer();
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auto const recv_counts = result.extract_recv_counts();
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auto const recv_displs = result.extract_recv_displs();
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}
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{ // C++ views can be used to send parts of the data.
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input.resize(comm.rank() + 1, comm.rank_signed());
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// Note, if you're on C++ >= 20 you can use std::span instead.
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comm.allgatherv(send_buf(kamping::Span(input).subspan(0, comm.rank())));
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97+
// Alternatively
98+
comm.allgatherv(send_buf(input), send_count(comm.rank_signed()));
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// let's restore the input
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input.resize(comm.rank());
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}
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}
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{
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// if you don't want to polute your global namespace with all KaMPIng's symbols, you can just use the namespace
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// for named parameters
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using namespace kamping::params;
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auto const output = comm.allgatherv(send_buf(input));
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print_result_on_root(output, comm);
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}
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46-
{ // We can also request the number of elements received from each rank. The recv_buf will always be the first out
47-
// parameter. After that, the output parameters are ordered as they appear in the function call.
48-
// KaMPIng calls like allgatherv return a result object which can be decomposed using structured
49-
// bindings (here) or explicit extract_*() calls (see below).
50-
auto [recv_buffer, recv_counts] = comm.allgatherv(send_buf(input), recv_counts_out());
51-
}
52-
53-
{ // To re-use memory, we can provide an already allocated container to the MPI call.
54-
std::vector<int> output;
55-
// Let KaMPIng resize the recv_buffer to the correct size. Other possibilities are no_resize and grow_only.
56-
comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output));
57-
58-
// We can also re-use already allocated containers for the other output parameters, e.g. recv_counts.
59-
std::vector<int> output_counts(comm.size());
60-
std::iota(output_counts.begin(), output_counts.end(), 0);
61-
comm.allgatherv(send_buf(input), recv_buf<resize_to_fit>(output), recv_counts(output_counts));
62-
63-
std::vector<int> displacements(comm.size());
64-
std::exclusive_scan(output_counts.begin(), output_counts.end(), displacements.begin(), 0);
65-
output.clear();
66-
67-
// In this example, we combine all of the concepts mentioned above:
68-
// - Use input as the send buffer
69-
// - Receive all elements into recv_buffer, resizing it to fit exactly the number of elements received.
70-
// - Output the number of elements received from each rank into recv_counts.
71-
// - Output the displacement of the first element received from each rank into recv_displs.
72-
comm.allgatherv(
73-
send_buf(input),
74-
recv_buf<resize_to_fit>(output),
75-
recv_counts(output_counts),
76-
recv_displs(displacements)
77-
);
78-
}
79-
80-
{ // It is also possible to use result.extract_*() calls instead of decomposing the result object using structured
81-
// bindings in order to increase readability.
82-
auto result = comm.allgatherv(send_buf(input), recv_counts_out(), recv_displs_out());
83-
auto const recv_buffer = result.extract_recv_buffer();
84-
auto const recv_counts = result.extract_recv_counts();
85-
auto const recv_displs = result.extract_recv_displs();
86-
}
87-
88-
{ // C++ views can be used to send parts of the data.
89-
input.resize(comm.rank() + 1, comm.rank_signed());
90-
91-
// Note, if you're on C++ >= 20 you can use std::span instead.
92-
comm.allgatherv(send_buf(kamping::Span(input).subspan(0, comm.rank())));
93-
94-
// Alternatively
95-
comm.allgatherv(send_buf(input), send_count(comm.rank_signed()));
111+
{
112+
// you can also define a shorthand for the named parameter namespace, to reduce code verbosity
113+
namespace kmp = kamping::params;
114+
auto const output = comm.allgatherv(kmp::send_buf(input));
115+
print_result_on_root(output, comm);
96116
}
97117

98118
return 0;

‎include/kamping/named_parameters.hpp

+5
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,8 @@ namespace internal {
3636
struct unused_tparam {};
3737
} // namespace internal
3838

39+
namespace params {
40+
3941
//// @addtogroup kamping_named_parameters
4042
/// @{
4143

@@ -1319,4 +1321,7 @@ inline auto send_recv_type_out(MPI_Datatype& send_recv_type) {
13191321
MPI_Datatype>(send_recv_type);
13201322
}
13211323
/// @}
1324+
1325+
} // namespace params
1326+
using namespace params;
13221327
} // namespace kamping

‎include/kamping/named_parameters_detail/status_parameters.hpp

+4
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,4 @@
1+
12
// This file is part of KaMPIng.
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//
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// Copyright 2023-2024 The KaMPIng Authors
@@ -20,6 +21,7 @@
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#include "kamping/status.hpp"
2122

2223
namespace kamping {
24+
namespace params {
2325
/// @addtogroup kamping_mpi_utility
2426
/// @{
2527

@@ -110,4 +112,6 @@ inline auto statuses_out() {
110112
}
111113

112114
/// @}
115+
} // namespace params
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using namespace params;
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} // namespace kamping

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