Handle possible overflow in TrustRegionStepEvaluator.
Thanks to Volker Grabe for reporting the problem and suggesting
a fix.
Change-Id: I8072ffb275907baac62ee2ad84a02f17eb447c63
diff --git a/internal/ceres/trust_region_step_evaluator.cc b/internal/ceres/trust_region_step_evaluator.cc
index c9167e6..33b0c41 100644
--- a/internal/ceres/trust_region_step_evaluator.cc
+++ b/internal/ceres/trust_region_step_evaluator.cc
@@ -29,6 +29,7 @@
// Author: sameeragarwal@google.com (Sameer Agarwal)
#include <algorithm>
+#include <limits>
#include "ceres/trust_region_step_evaluator.h"
#include "glog/logging.h"
@@ -51,6 +52,15 @@
double TrustRegionStepEvaluator::StepQuality(
const double cost,
const double model_cost_change) const {
+ // If the function evaluation for this step was a failure, in which
+ // case the TrustRegionMinimizer would have set the cost to
+ // std::numeric_limits<double>::max(). In this case, the division by
+ // model_cost_change can result in an overflow. To prevent that from
+ // happening, we will deal with this case explicitly.
+ if (cost >= std::numeric_limits<double>::max()) {
+ return std::numeric_limits<double>::lowest();
+ }
+
const double relative_decrease = (current_cost_ - cost) / model_cost_change;
const double historical_relative_decrease =
(reference_cost_ - cost) /
