Add an example Makefile for using Ceres.

Using Ceres in your application involves linking several dependent
libraries, depending on how you compiled Ceres. The example makes
it easier for users to leverage Ceres in their applications.

Change-Id: I6331fd9c6e36c3eac464be2a7a6b905cc76ed843

examples/Makefile.example

@@ -0,0 +1,82 @@
+# Ceres Solver - A fast non-linear least squares minimizer
+# Copyright 2012 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: keir@google.com (Keir Mierle)
+#
+# This is an example Makefile for using Ceres. In practice, the Ceres authors
+# suggest using CMake instead, but if Make is needed for some reason, this
+# example serves to make it easy to do so.
+
+# This should point to place where you unpacked or cloned Ceres.
+CERES_SRC_DIR := /home/keir/wrk/ceres-extra
+
+# This should point to the place where you built Ceres. If you got Ceres by
+# installing it, then this will likely be /usr/local/lib.
+CERES_BIN_DIR := /home/keir/wrk/ceres-extra-bin
+
+# The place you unpacked or cloned Eigen. If Eigen was installed from packages,
+# this will likely be /usr/local/include.
+EIGEN_SRC_DIR := /home/keir/src/eigen-3.0.5
+
+INCLUDES := -I$(CERES_SRC_DIR)/include \
+            -I$(EIGEN_SRC_DIR)
+
+CERES_LIBRARY := -lceres
+CERES_LIBRARY_PATH := -L$(CERES_BIN_DIR)/lib
+CERES_LIBRARY_DEPENDENCIES = -lgflags -lglog
+
+# If Ceres was built with Suitesparse:
+CERES_LIBRARY_DEPENDENCIES += -llapack -lcamd -lamd -lccolamd -lcolamd -lcholmod
+
+# If Ceres was built with CXSparse:
+CERES_LIBRARY_DEPENDENCIES += -lcxsparse
+
+# If Ceres was built with OpenMP:
+CERES_LIBRARY_DEPENDENCIES += -fopenmp -lpthread -lgomp -lm
+
+# The set of object files for your application.
+APPLICATION_OBJS := simple_bundle_adjuster.o
+
+all: simple_bundle_adjuster
+
+simple_bundle_adjuster: $(APPLICATION_OBJS)
+	g++ \
+		$(APPLICATION_OBJS) \
+		$(CERES_LIBRARY_PATH) \
+		$(CERES_LIBRARY) \
+		$(CERES_LIBRARY_DEPENDENCIES) \
+		-o simple_bundle_adjuster
+
+# Disabling debug asserts via -DNDEBUG helps make Eigen faster, at the cost of
+# not getting handy assert failures when there are issues in your code.
+CFLAGS := -O2 -DNDEBUG
+
+# If you have files ending in .cpp instead of .cc, fix the next line
+# appropriately.
+%.o: %.cc $(DEPS)
+	g++ -c -o $@ $< $(CFLAGS) $(INCLUDES)