A number of bug fixes.

1. Fix a build breakage in graph_test.
2. Respect Solver::Options::min_num_linear_solver_iterations in
   conjugate_gradients_solver.cc

Thanks to Johannes Schönberger for reporting these.

Change-Id: Ib32e3929bf5d92dd576ae5b53d4d88797095136e

docs/source/solving.rst

@@ -1304,7 +1304,7 @@ elimination group [LiSaad]_.
 
 .. member:: int Solver::Options::min_linear_solver_iterations
 
-   Default: ``1``
+   Default: ``0``
 
    Minimum number of iterations used by the linear solver. This only
    makes sense when the linear solver is an iterative solver, e.g.,

include/ceres/solver.h

@@ -120,7 +120,7 @@ class CERES_EXPORT Solver {
       num_linear_solver_threads = 1;
       use_postordering = false;
       dynamic_sparsity = false;
-      min_linear_solver_iterations = 1;
+      min_linear_solver_iterations = 0;
       max_linear_solver_iterations = 500;
       eta = 1e-1;
       jacobi_scaling = true;

internal/ceres/conjugate_gradients_solver.cc

@@ -101,7 +101,7 @@ LinearSolver::Summary ConjugateGradientsSolver::Solve(
   A->RightMultiply(x, tmp.data());
   r = bref - tmp;
   double norm_r = r.norm();
-  if (norm_r <= tol_r) {
+  if (options_.min_num_iteratios == 0 && norm_r <= tol_r) {
     summary.termination_type = LINEAR_SOLVER_SUCCESS;
     summary.message =
         StringPrintf("Convergence. |r| = %e <= %e.", norm_r, tol_r);
@@ -114,7 +114,8 @@ LinearSolver::Summary ConjugateGradientsSolver::Solve(
   double Q0 = -1.0 * xref.dot(bref + r);
 
   for (summary.num_iterations = 1;
-       summary.num_iterations < options_.max_num_iterations;
+       summary.num_iterations > options_.min_num_iterations &&
+       summary.num_iterations < options_.max_num_iterations
        ++summary.num_iterations) {
     // Apply preconditioner
     if (per_solve_options.preconditioner != NULL) {

internal/ceres/graph_test.cc

@@ -58,14 +58,14 @@ TEST(Graph, AddVertexIdempotence) {
   Graph<int> graph;
   graph.AddVertex(0);
   graph.AddVertex(1);
-  graph.AddEdge(0, 1)
+  graph.AddEdge(0, 1);
 
   const HashSet<int>& vertices = graph.vertices();
 
   EXPECT_EQ(vertices.size(), 2);
 
   // Try adding the vertex again with a new weight.
-  graph.AddVertex(0, 3.0);
+  graph.AddVertex(0);
   EXPECT_EQ(vertices.size(), 2);
 
   // Rest of the graph remains the same.