From 869b4443ac4a55c09a0632e2dbf621587749e164 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Mon, 25 Jan 2016 11:55:39 +0100
Subject: [PATCH] Add SparseVector::conservativeResize() method.

---
 Eigen/src/SparseCore/SparseVector.h | 18 ++++++++++
 test/sparse_vector.cpp              | 54 ++++++++++++++++++++++++-----
 2 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/Eigen/src/SparseCore/SparseVector.h b/Eigen/src/SparseCore/SparseVector.h
index 7ec73a365..4db3003d2 100644
--- a/Eigen/src/SparseCore/SparseVector.h
+++ b/Eigen/src/SparseCore/SparseVector.h
@@ -222,6 +222,24 @@ class SparseVector
       m_data.clear();
     }
 
+    /** Resizes the sparse vector to \a newSize, while leaving old values untouched.
+      *
+      * If the size of the vector is decreased, then the storage of the out-of bounds coefficients is kept and reserved.
+      * Call .data().squeeze() to free extra memory.
+      *
+      * \sa reserve(), setZero()
+      */
+    void conservativeResize(Index newSize)
+    {
+      if (newSize < m_size)
+      {
+        Index i = 0;
+        while (i<m_data.size() && m_data.index(i)<newSize) ++i;
+        m_data.resize(i);
+      }
+      m_size = newSize;
+    }
+
     void resizeNonZeros(Index size) { m_data.resize(size); }
 
     inline SparseVector() : m_size(0) { check_template_parameters(); resize(0); }
diff --git a/test/sparse_vector.cpp b/test/sparse_vector.cpp
index d3975b99b..d95f301d5 100644
--- a/test/sparse_vector.cpp
+++ b/test/sparse_vector.cpp
@@ -9,14 +9,14 @@
 
 #include "sparse.h"
 
-template<typename Scalar,typename Index> void sparse_vector(int rows, int cols)
+template<typename Scalar,typename StorageIndex> void sparse_vector(int rows, int cols)
 {
   double densityMat = (std::max)(8./(rows*cols), 0.01);
   double densityVec = (std::max)(8./float(rows), 0.1);
   typedef Matrix<Scalar,Dynamic,Dynamic> DenseMatrix;
   typedef Matrix<Scalar,Dynamic,1> DenseVector;
-  typedef SparseVector<Scalar,0,Index> SparseVectorType;
-  typedef SparseMatrix<Scalar,0,Index> SparseMatrixType;
+  typedef SparseVector<Scalar,0,StorageIndex> SparseVectorType;
+  typedef SparseMatrix<Scalar,0,StorageIndex> SparseMatrixType;
   Scalar eps = 1e-6;
 
   SparseMatrixType m1(rows,rows);
@@ -87,8 +87,10 @@ template<typename Scalar,typename Index> void sparse_vector(int rows, int cols)
 
   VERIFY_IS_APPROX(m1*v2, refM1*refV2);
   VERIFY_IS_APPROX(v1.dot(m1*v2), refV1.dot(refM1*refV2));
-  int i = internal::random<int>(0,rows-1);
-  VERIFY_IS_APPROX(v1.dot(m1.col(i)), refV1.dot(refM1.col(i)));
+  {
+    int i = internal::random<int>(0,rows-1);
+    VERIFY_IS_APPROX(v1.dot(m1.col(i)), refV1.dot(refM1.col(i)));
+  }
 
 
   VERIFY_IS_APPROX(v1.squaredNorm(), refV1.squaredNorm());
@@ -111,15 +113,51 @@ template<typename Scalar,typename Index> void sparse_vector(int rows, int cols)
   VERIFY_IS_APPROX(refV3 = v1.transpose(),v1.toDense()); 
   VERIFY_IS_APPROX(DenseVector(v1),v1.toDense()); 
 
+  // test conservative resize
+  {
+    std::vector<StorageIndex> inc;
+    if(rows > 3)
+      inc.push_back(-3);
+    inc.push_back(0);
+    inc.push_back(3);
+    inc.push_back(1);
+    inc.push_back(10);
+
+    for(std::size_t i = 0; i< inc.size(); i++) {
+      StorageIndex incRows = inc[i];
+      SparseVectorType vec1(rows);
+      DenseVector refVec1 = DenseVector::Zero(rows);
+      initSparse<Scalar>(densityVec, refVec1, vec1);
+
+      vec1.conservativeResize(rows+incRows);
+      refVec1.conservativeResize(rows+incRows);
+      if (incRows > 0) refVec1.tail(incRows).setZero();
+
+      VERIFY_IS_APPROX(vec1, refVec1);
+
+      // Insert new values
+      if (incRows > 0)
+        vec1.insert(vec1.rows()-1) = refVec1(refVec1.rows()-1) = 1;
+
+      VERIFY_IS_APPROX(vec1, refVec1);
+    }
+  }
+
 }
 
 void test_sparse_vector()
 {
   for(int i = 0; i < g_repeat; i++) {
+    int r = Eigen::internal::random<int>(1,500), c = Eigen::internal::random<int>(1,500);
+    if(Eigen::internal::random<int>(0,4) == 0) {
+      r = c; // check square matrices in 25% of tries
+    }
+    EIGEN_UNUSED_VARIABLE(r+c);
+
     CALL_SUBTEST_1(( sparse_vector<double,int>(8, 8) ));
-    CALL_SUBTEST_2(( sparse_vector<std::complex<double>, int>(16, 16) ));
-    CALL_SUBTEST_1(( sparse_vector<double,long int>(299, 535) ));
-    CALL_SUBTEST_1(( sparse_vector<double,short>(299, 535) ));
+    CALL_SUBTEST_2(( sparse_vector<std::complex<double>, int>(r, c) ));
+    CALL_SUBTEST_1(( sparse_vector<double,long int>(r, c) ));
+    CALL_SUBTEST_1(( sparse_vector<double,short>(r, c) ));
   }
 }