Add new Schur specialization for 2, 4, 6.

The row, E, F block pattern 2, 4, 6 is a common one for
bundle adjustment with reprojection error (2 residuals),
homogeneous 3d points (4 params in the E-block), and camera
poses (3 rotation + 3 position = 6 params for the
F-block). This provides a major speedup for BA in the
TheiaSfM library and likely in other applications.

Change-Id: If5df8bfadc7f154856b74c3b38479c14856db47d

internal/ceres/generate_template_specializations.py

@@ -63,6 +63,7 @@ SPECIALIZATIONS = [(2, 2, 2),
                    (2, 3, "Eigen::Dynamic"),
                    (2, 4, 3),
                    (2, 4, 4),
+                   (2, 4, 6),
                    (2, 4, 8),
                    (2, 4, 9),
                    (2, 4, "Eigen::Dynamic"),

internal/ceres/generated/partitioned_matrix_view_2_4_6.cc

@@ -0,0 +1,58 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2017 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: sameeragarwal@google.com (Sameer Agarwal)
+//
+// Template specialization of PartitionedMatrixView.
+//
+// ========================================
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+//=========================================
+//
+// This file is generated using generate_template_specializations.py.
+
+// This include must come before any #ifndef check on Ceres compile options.
+#include "ceres/internal/port.h"
+
+#ifndef CERES_RESTRICT_SCHUR_SPECIALIZATION
+
+#include "ceres/partitioned_matrix_view_impl.h"
+#include "ceres/internal/eigen.h"
+
+namespace ceres {
+namespace internal {
+
+template class PartitionedMatrixView<2, 4, 6>;
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_RESTRICT_SCHUR_SPECIALIZATION

internal/ceres/generated/schur_eliminator_2_4_6.cc

@@ -0,0 +1,58 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2017 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: sameeragarwal@google.com (Sameer Agarwal)
+//
+// Template specialization of SchurEliminator.
+//
+// ========================================
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+// THIS FILE IS AUTOGENERATED. DO NOT EDIT.
+//=========================================
+//
+// This file is generated using generate_template_specializations.py.
+
+// This include must come before any #ifndef check on Ceres compile options.
+#include "ceres/internal/port.h"
+
+#ifndef CERES_RESTRICT_SCHUR_SPECIALIZATION
+
+#include "ceres/schur_eliminator_impl.h"
+#include "ceres/internal/eigen.h"
+
+namespace ceres {
+namespace internal {
+
+template class SchurEliminator<2, 4, 6>;
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_RESTRICT_SCHUR_SPECIALIZATION

internal/ceres/partitioned_matrix_view.cc

@@ -103,6 +103,11 @@ PartitionedMatrixViewBase::Create(const LinearSolver::Options& options,
      (options.f_block_size == 4)) {
    return new PartitionedMatrixView<2, 4, 4>(matrix, options.elimination_groups[0]);
  }
+ if ((options.row_block_size == 2) &&
+     (options.e_block_size == 4) &&
+     (options.f_block_size == 6)) {
+   return new PartitionedMatrixView<2, 4, 6>(matrix, options.elimination_groups[0]);
+ }
  if ((options.row_block_size == 2) &&
      (options.e_block_size == 4) &&
      (options.f_block_size == 8)) {

internal/ceres/schur_eliminator.cc

@@ -102,6 +102,11 @@ SchurEliminatorBase::Create(const LinearSolver::Options& options) {
      (options.f_block_size == 4)) {
    return new SchurEliminator<2, 4, 4>(options);
  }
+ if ((options.row_block_size == 2) &&
+     (options.e_block_size == 4) &&
+     (options.f_block_size == 6)) {
+   return new SchurEliminator<2, 4, 6>(options);
+ }
  if ((options.row_block_size == 2) &&
      (options.e_block_size == 4) &&
      (options.f_block_size == 8)) {

internal/ceres/schur_templates.cc

@@ -142,6 +142,14 @@ void GetBestSchurTemplateSpecialization(int* row_block_size,
    *f_block_size = 4;
   return;
  }
+ if ((options.row_block_size == 2) &&
+     (options.e_block_size == 4) &&
+     (options.f_block_size == 6)) {
+   *row_block_size = 2;
+   *e_block_size = 4;
+   *f_block_size = 6;
+  return;
+ }
  if ((options.row_block_size == 2) &&
      (options.e_block_size == 4) &&
      (options.f_block_size == 8)) {