From 3695bf46952108e2c5e1b6123b19146b19b5844e Mon Sep 17 00:00:00 2001
From: Houtan Bastani <houtan@dynare.org>
Date: Wed, 27 Jul 2016 15:01:54 -0400
Subject: [PATCH] preprocessor: Return equation numbers/tags in error message
 when linear model contains nonzero hessian entries. #419

---
 preprocessor/DynamicModel.cc | 18 ++++++++++++++++++
 preprocessor/DynamicModel.hh |  3 +++
 preprocessor/ModFile.cc      | 12 +++++++++++-
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/preprocessor/DynamicModel.cc b/preprocessor/DynamicModel.cc
index 6d68eb425..20f8eb2cb 100644
--- a/preprocessor/DynamicModel.cc
+++ b/preprocessor/DynamicModel.cc
@@ -1731,6 +1731,24 @@ DynamicModel::reform(const string name1) const
   return (name);
 }
 
+void
+DynamicModel::getNonZeroHessianEquations(map<int, string> &eqs) const
+{
+  for (second_derivatives_t::const_iterator it = second_derivatives.begin();
+       it != second_derivatives.end(); it++)
+    if (eqs.find(it->first.first) == eqs.end())
+      {
+        eqs[it->first.first] = "";
+        for (size_t i = 0; i < equation_tags.size(); i++)
+          if (equation_tags[i].first == it->first.first)
+            if (equation_tags[i].second.first == "name")
+              {
+                eqs[it->first.first] = equation_tags[i].second.second;
+                break;
+              }
+      }
+}
+
 void
 DynamicModel::Write_Inf_To_Bin_File_Block(const string &dynamic_basename, const string &bin_basename, const int &num,
                                           int &u_count_int, bool &file_open, bool is_two_boundaries) const
diff --git a/preprocessor/DynamicModel.hh b/preprocessor/DynamicModel.hh
index 9c0e670ff..6b99423c7 100644
--- a/preprocessor/DynamicModel.hh
+++ b/preprocessor/DynamicModel.hh
@@ -220,6 +220,9 @@ public:
   //! Return true if the hessian is equal to zero
   inline bool checkHessianZero() const;
 
+  //! Return equations that have non-zero second derivatives
+  void getNonZeroHessianEquations(map<int, string> &eqs) const;
+
   //! Adds informations for simulation in a binary file
   void Write_Inf_To_Bin_File_Block(const string &dynamic_basename, const string &bin_basename,
                                    const int &num, int &u_count_int, bool &file_open, bool is_two_boundaries) const;
diff --git a/preprocessor/ModFile.cc b/preprocessor/ModFile.cc
index 414a51308..e828fa45e 100644
--- a/preprocessor/ModFile.cc
+++ b/preprocessor/ModFile.cc
@@ -536,7 +536,17 @@ ModFile::computingPass(bool no_tmp_terms, FileOutputType output, bool compute_xr
 
       if (linear && !dynamic_model.checkHessianZero())
         {
-          cerr << "ERROR: If the model is declared linear the second derivatives must be equal to zero." << endl;
+          map<int, string> eqs;
+          dynamic_model.getNonZeroHessianEquations(eqs);
+          cerr << "ERROR: If the model is declared linear the second derivatives must be equal to zero." << endl
+               << "       The following equations had non-zero second derivatives:" << endl;
+          for (map<int, string >::const_iterator it = eqs.begin(); it != eqs.end(); it++)
+            {
+              cerr << "       * Eq # " << it->first+1;
+              if (!it->second.empty())
+                cerr << " [" << it->second << "]";
+              cerr << endl;
+            }
           exit(EXIT_FAILURE);
         }
     }