feat: Add option to write Lagrange multipliers to output files

include/scopi/params.hpp

@@ -113,11 +113,17 @@ namespace scopi
          */
         std::string filename;
         /**
-         * @brief Whether to write the velocity and the rotation velocity of the particles in the output files.
+         * @brief Specifies if particle speed and rotation rate are to be written to output files.
          *
          * Default value is false.
          */
         bool write_velocity;
+        /**
+         * @brief Specifies if Lagrange multipliers are to be written to output files.
+         *
+         * Default value is false.
+         */
+        bool write_lagrange_multiplier;
         /**
          * @brief true for binary output files, false for text files.
          *

include/scopi/solver.hpp

@@ -407,9 +407,15 @@ namespace scopi
 
         json_output["contacts"] = {};
 
+        const auto& lambda = m_optim_solver.lagrange_multiplier();
+        std::size_t ic = 0;
         for (const auto& c : contacts)
         {
             json_output["contacts"].push_back(c.to_json());
+            if (m_params.write_lagrange_multiplier)
+            {
+                json_output["contacts"].back()["lagrange multiplier"] = xt::view(lambda, ic++);
+            }
         }
 
         if (m_params.binary_output)

src/params.cpp

@@ -8,6 +8,7 @@ namespace scopi
         , path(std::filesystem::current_path() / "Results")
         , filename("scopi_objects")
         , write_velocity(false)
+        , write_lagrange_multiplier(false)
         , binary_output(false)
     {
     }
@@ -22,6 +23,7 @@ namespace scopi
             opt->add_option("--filename", filename, "Name of the outputs")->capture_default_str();
             opt->add_option("--freq", output_frequency, "Output frequency (in iterations)")->capture_default_str();
             opt->add_flag("--write-velocity", write_velocity, "Write the velocity of objects")->capture_default_str();
+            opt->add_flag("--write-lagrange-multiplier", write_lagrange_multiplier, "Write the Lagrange multiplier for each contact")->capture_default_str();
             opt->add_flag("--binary-output", binary_output, "Write bson output file instead of json")->capture_default_str();
         }
     }