[PERFORMANCE] Should now perform tests in parallel using the ctest -j flag according to how many cores there are in the system.

cmake/GtsamTesting.cmake

@@ -97,10 +97,42 @@ else()
 	option(GTSAM_SINGLE_TEST_EXE "Combine unit tests into single executable (faster compile)" OFF)
 endif()
 mark_as_advanced(GTSAM_SINGLE_TEST_EXE)
+#Parallelize CTests since ctest supports the -j command
+#Get number of cores from here: https://cmake.org/pipermail/cmake/2010-October/040122.html
+if(NOT DEFINED PROCESSOR_COUNT)
+	# Unknown:
+	set(PROCESSOR_COUNT 0)
+
+	# Linux:
+	set(cpuinfo_file "/proc/cpuinfo")
+	if(EXISTS "${cpuinfo_file}")
+		file(STRINGS "${cpuinfo_file}" procs REGEX "^processor.: [0-9]+$")
+		list(LENGTH procs PROCESSOR_COUNT)
+	endif()
+
+	# Mac:
+	if(APPLE)
+		find_program(cmd_sys_pro "system_profiler")
+		if(cmd_sys_pro)
+			execute_process(COMMAND ${cmd_sys_pro} OUTPUT_VARIABLE info)
+			string(REGEX REPLACE "^.*Total Number Of Cores: ([0-9]+).*$" "\\1"
+					PROCESSOR_COUNT "${info}")
+		endif()
+	endif()
+
+	# Windows:
+	if(WIN32)
+		set(PROCESSOR_COUNT "$ENV{NUMBER_OF_PROCESSORS}")
+	endif()
+endif()
+
+if(PROCESSOR_COUNT)
+	set(CTEST_BUILD_FLAGS "-j${PROCESSOR_COUNT}")
+endif()
 
 # Enable make check (http://www.cmake.org/Wiki/CMakeEmulateMakeCheck)
 if(GTSAM_BUILD_TESTS)
-    add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION> --output-on-failure)
+    add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} ${CTEST_BUILD_FLAGS} -C $<CONFIGURATION> --output-on-failure)
 endif()
 
 # Add examples target