Running OpenCL Sample Application on Open-Q™ 820

OpenCL (Open Computing Language) is an industry standard that allows​​ software developers​​ to take advantage of​​ multiple processors in order to increase the performance of​​ computational tasks.​​ While originally​​ designed for desktop computers,​​ OpenCL​​ has​​ in recent years slowly​​ been​​ becoming​​ more​​ available on​​ embedded systems​​ as more​​ Graphics Processing Units​​ (GPUs)​​ become OpenCL compatible.​​ With the help of OpenCL,​​ GPUs​​ are able to​​ perform​​ intensive​​ parallel programming tasks​​ in graphics-related as well as​​ non-graphics related computational workloads, allowing for significantly improved processing times.​​ ​​ One of the​​ GPUs​​ used in smartphones and tablets that​​ now​​ supports OpenCL​​ is Qualcomm’s Adreno 530, which is used in Intrinsyc’s Open-Q 820 Development Kit.​​ 

In order to demonstrate the​​ decreased​​ processing time enabled by​​ OpenCL on the Adreno 530, a​​ sample application​​ originally​​ taken from the Sony Mobile website​​ [1]​​ will be used.​​ (This is not available on​​ the​​ Sony website any​​ more but​​ is available as archived pages [3], and in Github [4]).​​ Since the source code was originally targeted toward Sony Xperia devices​​ [2], it has been​​ slightly​​ modified for​​ use by the different hardware of​​ the Open-Q 820.​​ The sample application​​ applies​​ OpenCL to a math intensive bilateral filter operation on a​​ noisy​​ photo. In one case, the bilateral filter is applied using OpenCL, while in the second case it is applied using Native C.​​ While the execution time​​ improvements​​ may vary across different OpenCL-supported devices due to differences in​​ architecture,​​ executing​​ the​​ bilateral filter using OpenCL on the Open-Q 820​​ (GPU)​​ has demonstrated to be​​ over 300 times faster​​ than using Native C​​ (ARM/CPU).

The following sections​​ describe our modifications to​​ Sony’s sample application​​ that we performed for​​ the Open-Q 820.​​ Section​​ 1​​ illustrates​​ the expected behavior of the application​​ after modifying it for use on the Open-Q 820. Section​​ 2​​ describes the steps that were taken to modify the original sample application from Sony Mobile such that the source code could be built for Intrinsyc’s Open-Q 820. Section​​ 3​​ provides some suggestions for when troubleshooting is required.

Note: the instructions in this blog were tested for Open-Q 820 BSP Version​​ 4.1. These instructions may still work for other versions if OpenCL is supported on them. Please see Section​​ 3,​​ step 2 to check if OpenCL is supported.

Section​​ 1: Using the OpenCL Sample Application

Upon opening OpenCLexample1 on the device, a noisy image is shown along with three buttons.​​ 

The application will run a bilateral filter on the image to reduce the noise using either OpenCL or Native C, depending on which button is pressed.​​ Press Reset between running OpenCL and NativeC to ensure the bilateral filter is applied to the noisy image.​​ Pressing the OpenCL button should yield a much​​ faster​​ processing time than pressing the NativeC button​​ (for example, 5ms versus 1638ms). The processing time will be displayed at the top of the screen.

Section​​ 2: Modifying the Original OpenCL Sample Application to be built for the Open-Q 820

The following tutorial outlines the steps required to​​ modify​​ and build​​ Sony’s OpenCL code example,​​ taken from the Sony Mobile website,​​ using Android Studio​​ for Intrinsyc’s Open-Q 820 Development Kit.

Before initiating the steps below, ensure the latest NDK is set up by following steps at​​ https://developer.android.com/ndk/guides/index.html

• Download Sony’s OpenCL code example from​​ Github:

git clone https://github.com/alon21034/android-opencl-example.git​​ 

or from archived pages of original Sony website as in [3].

• Ensure NDK is set up:

https://developer.android.com/ndk/guides/index.html

• Import openclexample1 into Android Studio as a new project:

  • In Android Studio,​​ select​​ File​​ ​​ New​​ ​​ Import Project​​ (Gradle, Eclipse ADT, etc)

  • Select the location of​​ android-opencl-example/OpenCL_code_example/openclexample1

• • Create an import destination directory.

• • Click Finish with the default options selected

• Manually copy over any files from listed under "Ignored Files" in the generated import-summary.txt file.

• • For example, it may be necessary to manually copy over the following from the OpenCL_code_example/openclexample1 folder to the destination directory created in step 3c:

    • /OpenCL_code_example/openclexample1/extra_libs to /OpenCLSample/app/src/main/extra_libs

    • /OpenCL_code_example/openclexample1/include/ to /OpenCLSample/app/src/main/include

• Link C++ project with gradle:

  • Right-click the project in Android Studio ("app" in the project view) and select "Link C++ Project with Gradle"

• • Select ndk-build and the location of Android.mk for the Build System and Project Path, respectively.

• Replace libOpenCL.so with the one used by the device:

  • Use adb pull to get the file directly from the device.

adb pull vendor/lib64/libOpenCL.so

• • Replace​​ openclexample1/OpenCLSample/app/src/main/extra_libs/libOpenCL.so with this new libOpenCL.so file.

• The ABI used by the Open-Q 820 dev kit is arm64-v8a, which is supported as of SDK version 27. Therefore:

  • Modify the app level build.gradle file:

    • Change values of compileSdkVersion, minSdkVersion, and targetSdkVersion to 27.​​ (This is for Android Oreo 8.1. For other Android versions use SDK level corresponding to the version)

    • Add abiFilters ‘arm64-v8a’ to ndk (which should have been generated under defaultConfig).

• • Modify Application.mk:

    • Change the value of APP_ABI to arm64-v8a

    • Change the value of APP_PLATFORM to android-27

    • Change the value of APP_STL to c++_static from gnustl_static

• • • Open AndroidManifest.xml file, remove below lines from Manifest file.

<uses-sdk

android:minSdkVersion="14"

android:targetSdkVersion="17" />

Sync Project with Gradle Files.​​ (Option is on “Files” tab).

• Make Project using​​ Build​​ ​​ Make Project

Note:​​ If an error pops up regarding build:gradle, then install Google Maven repository and sync project.

• Either Run on the connected device (Run​​ Run ‘app’​​ Select a connected device), or Build APK (Build​​ ​​ Build APK), which can be installed using the method in step 2.​​ The application will appear on the device as OpenCLexample1.

Section​​ 3: Troubleshooting

If you are experiencing errors during the sync or build process, please try the following:

• Ensure you are using the latest version of Android Studio and NDK.​​ (The steps were tested on Android Studio 3.1)

• If you are not using​​ Open-Q820​​ BSP Version​​ 4.1, or if you are not using​​ the Intrinsyc Open-Q 820 Development Kit​​ you may need to:

  • Check to see if the OpenCL libraries exist on the device at the below locations​​ (For Android releases Oreo and above)​​ before proceeding to step b. If these files do not exist, it is very likely that OpenCL is not supported for the current software version.

/vendor/lib/libOpenCL.so

/vendor/lib64/libOpenCL.so

  For Android releases up to Nougat, check below locations.

/system/vendor/lib/libOpenCL.so

/system/vendor/lib64/libOpenCL.so

• • Use​​ libOpenCL.so​​ taken directly​​ from your device as in Section​​ 2​​ step​​ 6.

  • Ensure the correct ABI filter is listed​​ under abiFilters as in Section​​ 2​​ step​​ 7. You can check which ABI filter your device is using ADB in a terminal.

Note: only list the ABI filter you need, otherwise you may need to modify the extra_libs folder to include different versions of libOpenCL.so for different ABIs.

Section​​ 4: References

[1]​​ Rasmusson, J.​​ (2013, October 29). OpenCL code example. Retrieved May 2, 2017, from​​ https://developer.sonymobile.com/downloads/code-example-module/opencl-code-example/

[2]​​ Cuhrajs, S. (2013, November 14). Boost the performance of your Android app with OpenCL. Retrieved May 2, 2017, from​​ https://developer.sonymobile.com/knowledge-base/tutorials/android_tutorial/boost-the-performance-of-your-android-app-with-opencl/​​ 

[3]​​ https://web.archive.org/web/20160614053404/http://developer.sonymobile.com/knowledge-base/tutorials/android_tutorial/boost-the-performance-of-your-android-app-with-opencl/

https://web.archive.org/web/20160422125837/http://developer.sonymobile.com:80/downloads/code-example-module/opencl-code-example/

​​ [4]​​ https://github.com/alon21034/android-opencl-example

Author: Angela Rosa, Embedded Software Developer