RenderScriptDaniel Kao <daniel.kao@gmail.com>

Agenda

•What is RenderScript and why

•How to use it with REAL example

• Show some data comparison

•Bad side…

•References

What is RenderScript

• A framework for running computationally intensive tasks at high performance on Android.

• primarily oriented for use with data-parallel computation

• E.g., image processing, computational photography, or computer vision.

• run operations with automatic parallelization across all available processor cores, and supports different types of processors such as the CPU, GPU or DSP.

Why use it?

• If you use NDK

• Lack of portability

• Lack of performance (dealing with CPU, GPU, or DSP)

• Lack of usability (native code => harder, and JNI…)

• RenderScript did them all for you

How it works

1. Android app codes

2. RenderScript codes (C99-derived

language)

• Reflected Layer Classes

Developer’s job

System generated

Real Case

• Change white color to transparent for an image

Real Case

• Change white color to transparent for an image

Two important component

• compute kernels: written in a C99-derived language.

• Java codes:

• managing the lifetime of RenderScript resources

• controlling kernel execution.

Step 1: write .rs script

• Line 1: declares the version of RenderScript that you are Line • Line 2: declares the package name of the .java reflection of this RenderScript• Line 4-6: global static variables that can be accessed from java codes by system

generated java reflected functions• Line 8: kernel function definition• Line 9-61: where we write our codes• Line 62: return the result

Step 2: write java codes

• 121: Initialize a RenderScript context

• 122-124: Create Allocation (a RS object that provides storage for a fixed amount of data)

• 126: Create RS script object

• 133, 135: System generated func. to invoke computation for each element

Step 3: get data & clean memory

• Get the data from OutAllocation

• Manage memory in java codes

=> Destroy allocations and RenderScript instance

Data Comparison (contour)

• Almost always better than Java codes

Data Comparison (contour)

• Almost always better than Java codes

Bad Side….

• A framework that only works on Android platform

• Lack of documentation

• Limited API set

• Hard to debug

• Crashes on Intel Atom devices (my problem?)

References

• http://developer.android.com/guide/topics/renderscript/compute.html

• http://android-developers.blogspot.tw/2011/02/introducing-renderscript.html

• http://android-developers.blogspot.tw/2011/03/renderscript.html

• http://android-developers.blogspot.tw/2013/01/evolution-of-renderscript-performance.html

• https://www.youtube.com/watch?v=3ynA92x8WQo

• https://software.intel.com/en-us/articles/how-to-use-renderscript-on-intel-based-devices