add eoEvalNamedPipe

- a class to connect an external objective function through file(s)
- fix doc error in eoEvalCmd

eo/src/eoEvalNamedPipe.h

@@ -0,0 +1,120 @@
+/*
+(c) Thales group, 2020
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation;
+    version 2 of the License.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+Contact: http://eodev.sourceforge.net
+
+Authors:
+Johann Dréo <johann.dreo@thalesgroup.com>
+*/
+
+#ifndef eoEvalNamedPipe_H
+#define eoEvalNamedPipe_H
+
+#include <fstream>
+#include <sstream>
+#include <cstdlib>
+#include <array>
+
+#include "eoEvalFunc.h"
+#include "eoExceptions.h"
+
+/** Communicate through a named pipe FIFO to evaluate an individual.
+ *
+ * With this class, you can plug an external process computing the fitness
+ * of a serialized solution with a process hosting the EO algorithm.
+ * Both processes just have to read/write solutions/fitness in files.
+ *
+ * The code would work with any file, but it is actually only useful with
+ * FIFO pipes, which are blocking on I/O.
+ * Thus, the process actually computing the fitness will ait for the solution to be wrote,
+ * then compute and write the fitness back, waiting it to be read.
+ * Conversely, the EO process will wait after having wrote the solution, that the other process
+ * actually read it, then wait itself for the fitness to be read in the pipe.
+ * With pipes, the synchronization of the two processes is guaranteed.
+ *
+ * To create a named FIFO pipe under Linux, see the command `mkfifo`.
+ *
+ * @note: if you use a single pipe for input/output, take care
+ * of the synchronization with the process handling the fitness computation.
+ * In particular, the first call of eoEvalNamedPipe
+ * is to write the solution, THEN to read the fitness.
+ *
+ * @note Tested only under Unix systems, may not be portable as is.
+ *
+ * Use the default string serialization of the EOT and
+ * the default deserialization of the fitness.
+ *
+ *@ingroup Evaluation
+ */
+template<class EOT>
+class eoEvalNamedPipe : public eoEvalFunc< EOT >
+{
+public:
+    using Fitness = typename EOT::Fitness;
+
+    /** Constructor
+     *
+     * @param output_pipe_name The named pipe in which to write the serialized solution.
+     * @param input_pipe_name The named pipe in which to read the serialized fitness. If it is "", use the output pipe.
+     */
+    eoEvalNamedPipe(
+            const std::string output_pipe_name,
+            const std::string input_pipe_name = ""
+        ) :
+        _output_pipe_name(output_pipe_name),
+        _input_pipe_name(input_pipe_name)
+    {
+        if( _input_pipe_name == "") {
+            _input_pipe_name = _output_pipe_name;
+        }
+    }
+
+    virtual void operator()( EOT& sol )
+    {
+        // Any modification to sol would makes it invalid,
+        // it is thus useless to evaluate it, if it is not invalid.
+        if(not sol.invalid()) {
+            return;
+        }
+
+        sol.fitness( call( sol ) );
+    }
+
+private:
+    const std::string _output_pipe_name;
+    std::string _input_pipe_name;
+
+    Fitness call( EOT& sol )
+    {
+        // Write the passed solution.
+        std::ofstream out(_output_pipe_name);
+        out << sol << std::endl;
+        out.close();
+
+        // Read the output string in a valid fitness object.
+        Fitness fit;
+        std::ifstream if_fit(_input_pipe_name);
+        std::stringstream ss_fit;
+        ss_fit << if_fit.rdbuf();
+        if_fit.close();
+        ss_fit >> fit;
+
+        return fit;
+    }
+};
+
+#endif // eoEvalNamedPipe_H