Tutorial for connecting to Kratos and performing basic data exchange
Table of Contents
This tutorial shows how to establish a connection to Kratos and to do basics data exchange with Kratos. It is required to do this tutorial first.
Furthermore it is required to compile Kratos which is described here.
Connecting to Kratos
Instead of connecting two instances of the same code as shown in the previous tutorial, here one instance is connected to Kratos. For this we use the same code from the previous tutorial.
For connecting to Kratos it is very important to have in mind that Kratos also uses CoSimIO, so its python interface reflects the API of the CoSimIO. So we may create a python script for connecting and disconnecting in a similar way described in the python tutorial. The first step is to import the Kratos library:
# importing the CoSimIO of Kratos
from KratosMultiphysics.CoSimulationApplication import CoSimIO
A connection can be established after importing the Kratos library:
connection_settings = CoSimIO.Info()
connection_settings.SetString("my_name", "Kratos")
connection_settings.SetString("connect_to", "my_code")
connection_settings.SetInt("echo_level", 2)
info = CoSimIO.Connect(connection_settings)
connection_name = info.GetString("connection_name")
if info.GetInt("connection_status") != CoSimIO.ConnectionStatus.Connected:
raise Exception("Connecting failed")
The last step is to disconnect:
disconnect_settings = CoSimIO.Info()
disconnect_settings.SetString("connection_name", connection_name)
info = CoSimIO.Disconnect(disconnect_settings)
if info.GetInt("connection_status") != CoSimIO.ConnectionStatus.Disconnected:
raise Exception("Disconnecting failed")
Make sure to check that my_name and connect_to are set correctly, otherwise the connection can not be established. This was explained in more detail in a previous tutorial.
Please note that the only change here is the import statement which loads the CoSimIO module which comes inside the KratosMultiphysics. The python file with the full script can be found here
Then you may run your executable with python script of Kratos from your working directory:
path/to/connect_disconnect_cpp & python3 path/to/connect_disconnect.py
Data Exchange with Kratos
Here we try to send some data to Kratos and get it back from it. Then we can check if both data are the same. Again the python file for Kratos side is very similar to the one described in the python tutorial. First the Kratos library is imported and a connection is established:
from KratosMultiphysics.CoSimulationApplication import CoSimIO
connection_settings = CoSimIO.Info()
connection_settings.SetString("my_name", "Kratos")
connection_settings.SetString("connect_to", "my_code")
connection_settings.SetInt("echo_level", 0)
info = CoSimIO.Connect(connection_settings)
connection_name = info.GetString("connection_name")
if info.GetInt("connection_status") != CoSimIO.ConnectionStatus.Connected:
raise Exception("Connecting failed")
After the connection is established, the data can be imported, manipulated or printed if necessary and then exported back:
# first the data from "my_code" is received ...
import_info = CoSimIO.Info()
import_info.SetString("connection_name", connection_name)
import_info.SetString("identifier", "data_exchange_1")
imported_values = CoSimIO.DoubleVector()
CoSimIO.ImportData(import_info, imported_values)
# print(imported_values)
# ... then the data is sent back to "my_code"
export_info = CoSimIO.Info()
export_info.SetString("connection_name", connection_name)
export_info.SetString("identifier", "data_exchange_2")
CoSimIO.ExportData(export_info, imported_values)
As before the last step is to disconnect:
disconnect_settings = CoSimIO.Info()
disconnect_settings.SetString("connection_name", connection_name)
info = CoSimIO.Disconnect(disconnect_settings)
if info.GetInt("connection_status") != CoSimIO.ConnectionStatus.Disconnected:
raise Exception("Disconnecting failed")
The python file with the full script can be found here
On the other side we use first export data and then import it back, following what was done in this tutorial:
// System includes
#include <cmath> // std::abs
// CoSimulation includes
#include "co_sim_io.hpp"
#define COSIMIO_CHECK_EQUAL(a, b) \
if (a != b) { \
std::cout << "in line " << __LINE__ << " : " << a \
<< " is not equal to " << b << std::endl; \
return 1; \
}
int main()
{
CoSimIO::Info settings;
settings.Set("my_name", "my_code");
settings.Set("connect_to", "Kratos");
settings.Set("echo_level", 1);
auto info = CoSimIO::Connect(settings);
COSIMIO_CHECK_EQUAL(info.Get<int>("connection_status"), CoSimIO::ConnectionStatus::Connected);
const std::string connection_name = info.Get<std::string>("connection_name");
// send data to Kratos
std::vector<double> data_to_send(4, 3.14);
info.Clear();
info.Set("identifier", "data_exchange_1");
info.Set("connection_name", connection_name);
info = CoSimIO::ExportData(info, data_to_send);
// receive the same data from Kratos
std::vector<double> data_received;
info.Clear();
info.Set("identifier", "data_exchange_2");
info.Set("connection_name", connection_name);
info = CoSimIO::ImportData(info, data_received);
// check that the data is the same:
if (data_to_send.size() != data_received.size()) {
return 1;
}
for (std::size_t i=0; i<data_to_send.size(); ++i) {
// compare if values are the same, with a small tolerance
if (std::abs(data_to_send[i] - data_received[i]) > 1e-12) {
return 1;
}
}
// disconnecting afterwards
CoSimIO::Info disconnect_settings;
disconnect_settings.Set("connection_name", connection_name);
info = CoSimIO::Disconnect(disconnect_settings); // disconnect afterwards
COSIMIO_CHECK_EQUAL(info.Get<int>("connection_status"), CoSimIO::ConnectionStatus::Disconnected);
return 0;
}
This file can be found in integration_tutorials/cpp/data_exchange.cpp
Then you may run your executable with python script of Kratos from your working directory:
path/to/bin/data_exchange_cpp_test & python3 path/to/import_export_data.py
Next steps
In the next tutorial, meshes are exchanged with Kratos