diff --git a/internal/ceres/block_random_access_crs_matrix.cc b/internal/ceres/block_random_access_crs_matrix.cc
new file mode 100644
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+++ b/internal/ceres/block_random_access_crs_matrix.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2013 Google Inc. All rights reserved.
+// http://code.google.com/p/ceres-solver/
+//
+// 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)
+
+#include "ceres/block_random_access_crs_matrix.h"
+
+#include <algorithm>
+#include <set>
+#include <utility>
+#include <vector>
+#include "ceres/compressed_row_sparse_matrix.h"
+#include "ceres/internal/port.h"
+#include "ceres/internal/scoped_ptr.h"
+#include "ceres/mutex.h"
+#include "ceres/triplet_sparse_matrix.h"
+#include "ceres/types.h"
+#include "glog/logging.h"
+
+namespace ceres {
+namespace internal {
+
+BlockRandomAccessCRSMatrix::BlockRandomAccessCRSMatrix(
+    const vector<int>& blocks,
+    const set<pair<int, int> >& block_pairs)
+    : kMaxRowBlocks(10 * 1000 * 1000),
+      blocks_(blocks) {
+  CHECK_LT(blocks.size(), kMaxRowBlocks);
+
+  col_layout_.resize(blocks_.size(), 0);
+  row_strides_.resize(blocks_.size(), 0);
+
+  // Build the row/column layout vector and count the number of scalar
+  // rows/columns.
+  int num_cols = 0;
+  for (int i = 0; i < blocks_.size(); ++i) {
+    col_layout_[i] = num_cols;
+    num_cols += blocks_[i];
+  }
+
+  // Walk the sparsity pattern and count the number of non-zeros.
+  int num_nonzeros = 0;
+  for (set<pair<int, int> >::const_iterator it = block_pairs.begin();
+       it != block_pairs.end();
+       ++it) {
+    const int row_block_size = blocks_[it->first];
+    const int col_block_size = blocks_[it->second];
+    num_nonzeros += row_block_size * col_block_size;
+  }
+
+  VLOG(2) << "Matrix Size [" << num_cols
+          << "," << num_cols
+          << "] " << num_nonzeros;
+
+  crsm_.reset(new CompressedRowSparseMatrix(num_cols, num_cols, num_nonzeros));
+  int* rows = crsm_->mutable_rows();
+  int* cols = crsm_->mutable_cols();
+  double* values = crsm_->mutable_values();
+
+  // Iterate over the sparsity pattern and fill the scalar sparsity
+  // pattern of the underlying compressed sparse row matrix. Along the
+  // way also fill out the Layout object which will allow random
+  // access into the CRS Matrix.
+  set<pair<int, int> >::const_iterator it = block_pairs.begin();
+  vector<int> col_blocks;
+  int row_pos = 0;
+  rows[0] = 0;
+  while (it != block_pairs.end()) {
+    // Add entries to layout_ for all the blocks for this row.
+    col_blocks.clear();
+    const int row_block_id = it->first;
+    const int row_block_size = blocks_[row_block_id];
+    int num_cols = 0;
+    while ((it != block_pairs.end()) && (it->first == row_block_id)) {
+      layout_[IntPairToLong(it->first, it->second)] =
+          new CellInfo(values + num_cols);
+      col_blocks.push_back(it->second);
+      num_cols += blocks_[it->second];
+      ++it;
+    };
+
+    // Count the number of non-zeros in the row block.
+    for (int j = 0; j < row_block_size; ++j) {
+      rows[row_pos + j + 1] = rows[row_pos + j] + num_cols;
+    }
+
+    // Fill out the sparsity pattern for each row.
+    int col_pos = 0;
+    for (int j = 0; j < col_blocks.size(); ++j) {
+      const int col_block_id = col_blocks[j];
+      const int col_block_size = blocks_[col_block_id];
+      for (int r = 0; r < row_block_size; ++r) {
+        const int column_block_begin = rows[row_pos + r] + col_pos;
+        for (int c = 0; c < col_block_size; ++c) {
+          cols[column_block_begin + c] = col_layout_[col_block_id] + c;
+        }
+      }
+      col_pos += col_block_size;
+    }
+
+    row_pos += row_block_size;
+    values += row_block_size * num_cols;
+    row_strides_[row_block_id] = num_cols;
+  }
+}
+
+// Assume that the user does not hold any locks on any cell blocks
+// when they are calling SetZero.
+BlockRandomAccessCRSMatrix::~BlockRandomAccessCRSMatrix() {
+  // TODO(sameeragarwal) this should be rationalized going forward and
+  // perhaps moved into BlockRandomAccessMatrix.
+  for (LayoutType::iterator it = layout_.begin();
+       it != layout_.end();
+       ++it) {
+    delete it->second;
+  }
+}
+
+CellInfo* BlockRandomAccessCRSMatrix::GetCell(int row_block_id,
+                                              int col_block_id,
+                                              int* row,
+                                              int* col,
+                                              int* row_stride,
+                                              int* col_stride) {
+  const LayoutType::iterator it  =
+      layout_.find(IntPairToLong(row_block_id, col_block_id));
+  if (it == layout_.end()) {
+    return NULL;
+  }
+
+  *row = 0;
+  *col = 0;
+  *row_stride = blocks_[row_block_id];
+  *col_stride = row_strides_[row_block_id];
+  return it->second;
+}
+
+// Assume that the user does not hold any locks on any cell blocks
+// when they are calling SetZero.
+void BlockRandomAccessCRSMatrix::SetZero() {
+  crsm_->SetZero();
+}
+
+}  // namespace internal
+}  // namespace ceres