compiling fftw3 in android ndk

android-ndk

Solution

The FFTW3 build system makes use of Autotools, so that you can not use it directly with the Android NDK. A good blog post dealing with this issue is here.

The idea is to generate a proper `config.h` file offline and to create Android Makefiles, which replace the missing ones normally generated by the Autotools.

To achieve a modular layout for the different native modules you might use, I'd recommend the following:

In your top `jni/` directory put these two files:

`Application.mk`:

    APP_OPTIM        := release
    APP_ABI          := armeabi armeabi-v7a
    APP_MODULES      := fftw3

`Android.mk`:

    TOP_DIR := $(call my-dir)
    include $(TOP_DIR)/fftw3/project/jni/Android.mk

This way you can easily add a new module by creating a `jni/new_module_name` directory and then adding `new_module_name` to the `APP_MODULES` list.

Then create a new `jni/fftw3` directory and put another `Application.mk` there:

`Application.mk`:

    APP_PROJECT_PATH := $(call my-dir)/project
    APP_MODULES      += fftw3
    APP_OPTIM        := release
    APP_ABI          := armeabi armeabi-v7a

Then put the original FFTW3 package under `jni/fftw3/project/jni`.

At this point you need to generate a `config.h`. You can do this by using a small shell script like this.

The last step is to create the needed Android Makefile. In `jni/fftw3/project/jni` put a top `Android.mk`:

    LOCAL_PATH := $(call my-dir)
    include $(CLEAR_VARS)

    include $(LOCAL_PATH)/api/sources.mk
    include $(LOCAL_PATH)/dft/sources.mk
    include $(LOCAL_PATH)/dft/scalar/sources.mk
    include $(LOCAL_PATH)/dft/scalar/codelets/sources.mk
    include $(LOCAL_PATH)/kernel/sources.mk
    include $(LOCAL_PATH)/rdft/sources.mk
    include $(LOCAL_PATH)/rdft/scalar/sources.mk
    include $(LOCAL_PATH)/rdft/scalar/r2cb/sources.mk
    include $(LOCAL_PATH)/rdft/scalar/r2cf/sources.mk
    include $(LOCAL_PATH)/rdft/scalar/r2r/sources.mk
    include $(LOCAL_PATH)/reodft/sources.mk

    LOCAL_MODULE := fftw3
    LOCAL_C_INCLUDES := $(LOCAL_PATH) \
        $(LOCAL_PATH)/api \
        $(LOCAL_PATH)/dft \
        $(LOCAL_PATH)/dft/scalar \
        $(LOCAL_PATH)/dft/scalar/codelets \
        $(LOCAL_PATH)/kernel \
        $(LOCAL_PATH)/rdft \
        $(LOCAL_PATH)/rdft/scalar \
        $(LOCAL_PATH)/rdft/scalar/r2cb \
        $(LOCAL_PATH)/rdft/scalar/r2cf \
        $(LOCAL_PATH)/rdft/scalar/r2r \
        $(LOCAL_PATH)/reodft

    # Use APP_OPTIM in Application.mk
    LOCAL_CFLAGS := -g

    include $(BUILD_SHARED_LIBRARY)

Frow now on you have to create all these `sources.mk` files. E.g. a typical `sources.mk` looks like this:

`rdft/sources.mk`:

    sources = buffered2.c \
              buffered.c \
              <....>
              vrank-geq1.c \
              vrank-geq1-rdft2.c

    LOCAL_SRC_FILES += $(sources:%=rdft/%)

Call the `ndk-build` script in the top directory of your app and you should end up with two ready-to-use FFTW3 libraries:

- `libs/armeabi-v7a/libfftw3.so`

- `libs/armeabi/libfftw3.so`

Problem

hi i am new to android-ndk so far i worked with all sample applications in android-ndk,now i am trying to port fftw3 library in android, can you plz suggest me any tutorial for this. Thanks.

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