From d5b26c0d2d5912a85c0a62f3a075ef6d6f9f15a6 Mon Sep 17 00:00:00 2001
From: Gleb Belov <gleb@ampl.com>
Date: Fri, 3 May 2024 22:25:36 +1000
Subject: [PATCH] Marking: prepare for new expressions #237

---
 include/mp/flat/constr_2_expr.h   |  2 ++
 include/mp/flat/converter_model.h | 11 +++++++----
 include/mp/utils-vec.h            | 12 ++++++++++++
 solvers/scipmp/scipmpmodelapi.h   |  3 ++-
 4 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/include/mp/flat/constr_2_expr.h b/include/mp/flat/constr_2_expr.h
index d587b8485..a9536795d 100644
--- a/include/mp/flat/constr_2_expr.h
+++ b/include/mp/flat/constr_2_expr.h
@@ -61,6 +61,8 @@ class Constraints2Expr {
 
 protected:
   /// Algebraic cons: no marking (when NLConstraint accepted?)
+  /// @todo Do we need to consider NLConstraint / NLObjective at this step?
+  /// Are they added during marking?
   template <class Body, class RhsOrRange>
   void DoMarkArgsAsVars(   // needs to appear before the most generic template
       const AlgebraicConstraint<Body, RhsOrRange>& , int ) { }
diff --git a/include/mp/flat/converter_model.h b/include/mp/flat/converter_model.h
index 3ba5da29d..804bbece8 100644
--- a/include/mp/flat/converter_model.h
+++ b/include/mp/flat/converter_model.h
@@ -7,6 +7,8 @@
 #include <cmath>
 #include <cfloat>
 
+#include "mp/utils-vec.h"
+
 #include "mp/flat/obj_std.h"
 #include "mp/flat/constr_std.h"
 #include "mp/flat/constr_keeper.h"
@@ -235,18 +237,19 @@ class FlatModel
   }
 
   /// Mark as an explicit result variable
+  /// @todo AutoExpand fills 'false' for new elements...
   void MarkAsResultVar(int v) {
-    var_result_.at(v) = true;
+    AutoExpand(var_result_, v) = true;
   }
 
   /// Mark as a proper expression
   void MarkAsExpression(int v) {
-    var_result_.at(v) = false;
+    AutoExpand(var_result_, v) = false;
   }
 
   /// Is the variable an explicit result var?
-  bool IsResultVar(int v) const {
-    return var_result_.at(v);
+  bool IsResultVar(int v) {
+    return AutoExpand(var_result_, v);
   }
 
   ///////////////////////////// OBJECTIVES ////////////////////////////
diff --git a/include/mp/utils-vec.h b/include/mp/utils-vec.h
index 05e7f6e96..7db6e875f 100644
--- a/include/mp/utils-vec.h
+++ b/include/mp/utils-vec.h
@@ -4,6 +4,18 @@
 
 namespace mp {
 
+/// Grow vector capacity by a factor if needed.
+/// @return reference to the element at \a i.
+template <class Vec>
+auto AutoExpand(Vec& vec, typename Vec::size_type i) {
+  if (vec.size()<=i) {
+    if (vec.capacity()<=i)
+      vec.reserve(((i+1)*13)/10);
+    vec.resize(i+1);
+  }
+  return vec[i];
+}
+
 }  // namespace mp
 
 
diff --git a/solvers/scipmp/scipmpmodelapi.h b/solvers/scipmp/scipmpmodelapi.h
index 6f5144428..53c94e9af 100644
--- a/solvers/scipmp/scipmpmodelapi.h
+++ b/solvers/scipmp/scipmpmodelapi.h
@@ -66,8 +66,9 @@ class ScipModelAPI :
   /// For each expression,
   /// say ACCEPT_EXPRESSION(Recommended)
   /// or ACCEPT_EXPRESSION(AcceptedButNotRecommended).
+  /// This can be user-configured via options 'acc:exp' etc.
   ACCEPT_EXPRESSION(ExpExpression, Recommended)
-  void AddExpression(const ExpExpression& );
+  SCIP_EXPR* AddExpression(const ExpExpression& );
 
   /// The linear range constraint, if fully supported with basis info etc.
   ACCEPT_CONSTRAINT(LinConRange, Recommended, CG_Linear)