diff --git a/internal/ceres/context_impl.h b/internal/ceres/context_impl.h
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2018 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: vitus@google.com (Michael Vitus)
+
+#ifndef CERES_INTERNAL_CONTEXT_IMPL_H_
+#define CERES_INTERNAL_CONTEXT_IMPL_H_
+
+// This include must come before any #ifndef check on Ceres compile options.
+#include "ceres/internal/port.h"
+
+#include "ceres/context.h"
+
+#ifdef CERES_USE_CXX11_THREADS
+#include "ceres/thread_pool.h"
+#endif  // CERES_USE_CXX11_THREADS
+
+namespace ceres {
+namespace internal {
+
+class ContextImpl : public Context {
+ public:
+  ContextImpl() {}
+  ContextImpl(const ContextImpl&) = delete;
+  void operator=(const ContextImpl&) = delete;
+
+  virtual ~ContextImpl() {}
+
+  // When compiled with C++11 threading support, resize the thread pool to have
+  // at min(num_thread, num_hardware_threads) where num_hardware_threads is
+  // defined by the hardware.  Otherwise this call is a no-op.
+  void EnsureMinimumThreads(int num_threads);
+
+#ifdef CERES_USE_CXX11_THREADS
+  ThreadPool thread_pool;
+#endif  // CERES_USE_CXX11_THREADS
+};
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_INTERNAL_CONTEXT_IMPL_H_