improved exception message when there are lots of keys

gtsam/inference/inferenceExceptions.h

@@ -29,7 +29,7 @@ namespace gtsam {
  * full elimination routine was called with an ordering that does not include
  * all of the variables. */
 class InconsistentEliminationRequested : public std::exception {
-  KeySet keys_;
+  KeyVector keys_;
   const KeyFormatter& keyFormatter = DefaultKeyFormatter;
 
  public:
@@ -38,21 +38,26 @@ class InconsistentEliminationRequested : public std::exception {
   InconsistentEliminationRequested(
       const KeySet& keys,
       const KeyFormatter& key_formatter = DefaultKeyFormatter)
-      : keys_(keys), keyFormatter(key_formatter) {}
+      : keys_(keys.begin(), keys.end()), keyFormatter(key_formatter) {}
 
   ~InconsistentEliminationRequested() noexcept override {}
   const char* what() const noexcept override {
     // Format keys for printing
     std::stringstream sstr;
-    for (auto key : keys_) {
-      sstr << keyFormatter(key) << ", ";
+    size_t nrKeysToDisplay = std::min(size_t(4), keys_.size());
+    for (size_t i = 0; i < nrKeysToDisplay; i++) {
+      sstr << keyFormatter(keys_.at(i));
+      if (i < nrKeysToDisplay - 1) {
+        sstr << ", ";
       }
+    }
+    if (keys_.size() > nrKeysToDisplay) {
+      sstr << ", ... (total " << keys_.size() << " keys)";
+    }
+    sstr << ".";
     std::string keys = sstr.str();
-    // remove final comma and space.
-    keys.pop_back();
-    keys.pop_back();
 
-    static std::string msg =
+    std::string msg =
         "An inference algorithm was called with inconsistent "
         "arguments.  "
         "The\n"
@@ -64,7 +69,8 @@ class InconsistentEliminationRequested : public std::exception {
         "that\n"
         "does not include all of the variables.\n";
     msg += ("Leftover keys after elimination: " + keys);
-    return msg.c_str();
+    // `new` to allocate memory on heap instead of stack
+    return (new std::string(msg))->c_str();
   }
 };
 }  // namespace gtsam

gtsam/linear/tests/testGaussianFactorGraph.cpp

@@ -465,7 +465,31 @@ TEST(GaussianFactorGraph, InconsistentEliminationMessage) {
         "an ordering "
         "that\n"
         "does not include all of the variables.\n"
-        "Leftover keys after elimination: 2, x3";
+        "Leftover keys after elimination: 2, x3.";
+    EXPECT(expected_exception_message == exc.what());
+  }
+
+  // Test large number of keys
+  fg = GaussianFactorGraph();
+  for (size_t i = 0; i < 1000; i++) {
+    fg.emplace_shared<JacobianFactor>(i, -I_2x2, i + 1, I_2x2,
+                                      Vector2(2.0, -1.0), unit2);
+  }
+
+  try {
+    fg.eliminateSequential(ordering);
+  } catch (const exception& exc) {
+    std::string expected_exception_message = "An inference algorithm was called with inconsistent "
+        "arguments.  "
+        "The\n"
+        "factor graph, ordering, or variable index were "
+        "inconsistent with "
+        "each\n"
+        "other, or a full elimination routine was called with "
+        "an ordering "
+        "that\n"
+        "does not include all of the variables.\n"
+        "Leftover keys after elimination: 2, 3, 4, 5, ... (total 999 keys).";
     EXPECT(expected_exception_message == exc.what());
   }
 }