From 8da5bb00b690647318a12fa4f5dd7e6c8a0f501c Mon Sep 17 00:00:00 2001
From: martimbrandao <martimbrandao@gmail.com>
Date: Tue, 23 May 2017 23:35:18 +0900
Subject: [PATCH] save gurobi's Irreducible Infeasible Sets (IIS) for easier
 debug of infeasible optimization problems

---
 src/sco/gurobi_interface.cpp | 5 ++++-
 src/sco/optimizers.cpp       | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/sco/gurobi_interface.cpp b/src/sco/gurobi_interface.cpp
index 69140f76..1d438475 100644
--- a/src/sco/gurobi_interface.cpp
+++ b/src/sco/gurobi_interface.cpp
@@ -188,7 +188,10 @@ CvxOptStatus GurobiModel::optimize(){
     LOG_DEBUG("solver objective value: %.3e", objval);
     return CVX_SOLVED;
   }
-  else if (status == GRB_INFEASIBLE) return CVX_INFEASIBLE;
+  else if (status == GRB_INFEASIBLE) {
+    GRBcomputeIIS(m_model);
+    return CVX_INFEASIBLE;
+  }
   else return CVX_FAILED;
 }
 CvxOptStatus GurobiModel::optimizeFeasRelax(){
diff --git a/src/sco/optimizers.cpp b/src/sco/optimizers.cpp
index 8e37ba89..9f1000bf 100644
--- a/src/sco/optimizers.cpp
+++ b/src/sco/optimizers.cpp
@@ -289,8 +289,9 @@ OptStatus BasicTrustRegionSQP::optimize() {
         CvxOptStatus status = model_->optimize();
         ++results_.n_qp_solves;
         if (status != CVX_SOLVED) {
-          LOG_ERROR("convex solver failed! set TRAJOPT_LOG_THRESH=DEBUG to see solver output. saving model to /tmp/fail.lp");
+          LOG_ERROR("convex solver failed! set TRAJOPT_LOG_THRESH=DEBUG to see solver output. saving model to /tmp/fail.lp and IIS to /tmp/fail.ilp");
           model_->writeToFile("/tmp/fail.lp");
+          model_->writeToFile("/tmp/fail.ilp");
           retval = OPT_FAILED;
           goto cleanup;
         }