From 8282e76d6197f324d7051241fdf2766db2ca9017 Mon Sep 17 00:00:00 2001
From: Johannes Pfeifer <jpfeifer@gmx,de>
Date: Thu, 31 Oct 2013 08:07:55 +0100
Subject: [PATCH] Add more explicit information in case of singularity problem

---
 matlab/dynare_estimation_1.m | 2 +-
 matlab/model_diagnostics.m   | 7 +++++++
 matlab/print_info.m          | 3 ++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/matlab/dynare_estimation_1.m b/matlab/dynare_estimation_1.m
index 2c8783bfd..ec907da7b 100644
--- a/matlab/dynare_estimation_1.m
+++ b/matlab/dynare_estimation_1.m
@@ -646,7 +646,7 @@ if ~options_.mh_posterior_mode_estimation && options_.cova_compute
         disp('POSTERIOR KERNEL OPTIMIZATION PROBLEM!')
         disp(' (minus) the hessian matrix at the "mode" is not positive definite!')
         disp('=> posterior variance of the estimated parameters are not positive.')
-        disp('You should  try  to change the initial values of the parameters using')
+        disp('You should try to change the initial values of the parameters using')
         disp('the estimated_params_init block, or use another optimization routine.')
         params_at_bound=find(xparam1==ub | xparam1==lb);
         if ~isempty(params_at_bound)
diff --git a/matlab/model_diagnostics.m b/matlab/model_diagnostics.m
index 06eaf2bad..611ae9d38 100644
--- a/matlab/model_diagnostics.m
+++ b/matlab/model_diagnostics.m
@@ -85,6 +85,7 @@ end
 %
 % singular Jacobian of static model
 %
+singularity_problem = 0;
 if ~isfield(M,'block_structure_stat')
     nb = 1;
 else
@@ -107,6 +108,7 @@ for b=1:nb
     end
     rank_jacob = rank(jacob);
     if rank_jacob < size(jacob,1)
+        singularity_problem = 1;
         disp(['model_diagnostic: the Jacobian of the static model is ' ...
               'singular'])
         disp(['there is ' num2str(endo_nbr-rank_jacob) ...
@@ -143,4 +145,9 @@ for b=1:nb
         end
     end
 end
+if singularity_problem 
+    fprint('The presence of a singularity problem typically indicates that there is one\n')
+    fprint('redundant equation entered in the model block, while another non-redundant equation\n')
+    fprint('is missing. The problem often derives from Walras Law.\n')
+end
 
diff --git a/matlab/print_info.m b/matlab/print_info.m
index 157275fb4..e4fe151a5 100644
--- a/matlab/print_info.m
+++ b/matlab/print_info.m
@@ -36,7 +36,8 @@ if ~noprint
       case 2
         error(['The generalized Schur (QZ) decomposition failed. ' ...
                'For more information, see the documentation for Lapack function dgges: info=' ...
-               int2str(info(2)) ', n=' int2str(info(3))])
+               int2str(info(2)) ', n=' int2str(info(3)) ...
+               '. You can also run model_diagnostics to get more information on what may cause this problem.'])
       case 3
         error(['Blanchard Kahn conditions are not satisfied: no stable' ...
                ' equilibrium'])