Update MHTPParams: refactoring the ctor in .hpp (initializing all the...

Update MHTPParams: refactoring the ctor in .hpp (initializing all the attributes), adding a to_string member function.

src/algorithm/factorization/faust_MHTP.h

 #ifndef __MHTP__
 #define __MHTP__
+#include <string>
 namespace Faust
 {
+	/**
+	 * \brief This class represents the set of parameters used for the MHTP (Multilinear Hard Thresholding Pursuit) algorithm used optionally in PALM4MSA (2020 implementation only).
+	 *
+	 */
 	template<typename FPP>
 		struct MHTPParams
 		{
@@ -11,8 +16,9 @@ namespace Faust
 			FPP step_size;
 			int palm4msa_period;
 			bool updating_lambda;
-
-			MHTPParams() : used(false) {}; //TODO: move in faust_MHTP.hpp
+			MHTPParams();
+			std::string to_string() const;
 		};
 };
+#include "faust_MHTP.hpp"
 #endif

src/algorithm/factorization/faust_MHTP.hpp

+namespace Faust
+{
+	template<typename FPP>
+		MHTPParams<FPP>::MHTPParams() : used(false),
+		constant_step_size(false),
+		step_size(1e-3),
+		palm4msa_period(1000),
+		updating_lambda(true),
+		sc(StoppingCriterion<FPP>(50)){};
+
+	template<typename FPP>
+	std::string MHTPParams<FPP>::to_string() const
+	{
+		auto sc_str = sc.to_string();
+		std::string str = "MHTPParams (START):";
+		str += "\r\n";
+		str += "StoppingCriterion:";
+		str += "\r\n ===";
+		str += sc_str;
+		str += " === \r\n";
+		str += "constant_step_size: ";
+		str += std::to_string(constant_step_size);
+		str += "\r\n";
+		str += "step_size: ";
+		str += std::to_string(step_size);
+		str += "\r\n";
+		str += "palm4msa_period: ";
+		str += std::to_string(palm4msa_period);
+		str += "\r\n";
+		str += "updating_lambda: ";
+		str += std::to_string(updating_lambda);
+		str += "\r\n";
+		str += "MHTPParams END.";
+		return str;
+	}
+}