iOS framework is being built without optimization. (Bug #2232)

John, here is no Bug. You can profile your app and find, that routine started to consume more time as usual. If it's because OpenCV, you can ask about changes at http://answers.opencv.org/questions/.

Here's a hack to opencv/ios/build_framework.py to delete the offending code:

53a54,55

os.system("sed -i bak '/GCC_OPTIMIZATION_LEVEL/d' OpenCV.xcodeproj/project.pbxproj")

Obviously it would be better to fix the Cmake scripts, but this at least gets my frame rate back up to where it should be.

Daniil Osokin wrote:

John, here is no Bug. You can profile your app and find, that routine started to consume more time as usual. If it's because OpenCV, you can ask about changes at http://answers.opencv.org/questions/.

It is a real and genuine bug. OpenCV is building without optimization in release mode for iOS. If it were otherwise, my sed hack wouldn't drastically increase my frame rate.

Looks like the actual bug is in Cmake. The "ALL_BUILD" target for even a simple "Hello, world" project forces "-O0" for all build configurations, although the actual "Hello" target does not.

It appears that the Cmake-generated "ALL_BUILD" target in Xcode doesn't work in general. See for example:

"Note: ALL_BUILD does not work properly with Xcode 4."
http://www.ogre3d.org/tikiwiki/CMake+Quick+Start+Guide?tikiversion=Mac+OS+X

I'll look at patching the build_framework.py script to use a different build target tomorrow.

Ok, looking forward to a patch.

Hi all,

I don't know if this has already been solved, but my solution was to include a file "iOS-gcc.cmake" in ${OPENCV_ROOT}/ios/cmake/Modules/Platform, with the following contents:

SET (CMAKE_C_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")

SET (CMAKE_C_FLAGS_DEBUG_INIT "-O0 -gdwarf-2")
SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-O0 -gdwarf-2")

According to the CMake wiki (http://www.cmake.org/Wiki/CMake_Cross_Compiling), CMake will look for this file when crosscompiling. The variables are then set to the usual CMAKE_*_FLAGS_RELEASE or _DEBUG by CMake.

Cheers,
J.

My apologies for replying to myself.

After a cleanup it seems that setting this variables overwrites the CMAKE_CXX_FLAGS that are currently set in iOS.cmake. A solution is moving those values to the iOS-gcc.cmake file. My file looks like this, finally:

SET (CMAKE_CXX_FLAGS_INIT "-fvisibility=hidden -fvisibility-inlines-hidden")
SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-O0 -gdwarf-2")

Other variables for other CMAKE_BUILD_TYPE can be set that way too. (Maybe a better option would be to use a macro as in ${CMAKE_ROOT}/share/cmake-2.8/Modules/Compiler/GNU.cmake, but this does the trick for me.)
Regards,
J.

Usually, when dealing with compiler flags and CMake, it's a good idea to leave them as they are and only add new stuff because CMake already has a good set of default flags for Debug and Release.
However, I don't know about cross compiling here. Maybe the flags are wrong to start with.

Anyway, for now I just employed a hack with "-O3 -DNDEBUG -ffast-math" in the CMake files.