Increment A Count Variable In Renderscript

I want to count the pixels of a bitmap using the following RenderScript code RenderScript Filename: counter.rs #pragma version(1) #pragma rs java_package_name(com.mypackage) #pragm

Solution 1:

As a side note, it is usually not a good practice to use atomic operations in parallel computing unless you have to. RenderScript actually provide the reduction kernel for this kind of application. Maybe you can give it a try.

There several problems with the code:

1. The variable "count" should have been declared "volatile"
2. countPixels should have been "void RS_KERNEL countPixels(uchar4 in)"
3. script.get_count() will not get you the up-to-date value of "count", you have to get the value back with an Allocation.

If you have to use rsAtomicInc, a good example is actually the RenderScript CTS tests:

AtomicTest.rs

AtomicTest.java

Solution 2:

Here is my working solution.

RenderScript

Filename: counter.rs

#pragma version(1)#pragma rs java_package_name(com.mypackage)#pragma rs_fp_relaxed

int32_t count = 0;
rs_allocation rsAllocationCount;

voidcountPixels(uchar4* unused, uint x, uint y) {
  rsAtomicInc(&count);
  rsSetElementAt_int(rsAllocationCount, count, 0);
}

• rsAtomicInc()
• rsSetElementAt_int()

Java

Contextcontext= ...;
RenderScriptrenderScript= RenderScript.create(context);

Bitmapbitmap= ...; // A random bitmapAllocationallocationBitmap= Allocation.createFromBitmap(renderScript, bitmap);
AllocationallocationCount= Allocation.createTyped(renderScript, Type.createX(renderScript, Element.I32(renderScript), 1));

ScriptC_Counterscript=newScriptC_Counter(renderScript);
script.set_rsAllocationCount(allocationCount);
script.forEach_countPixels(allocationBitmap);

int[] count = newint[1];
allocationBitmap.syncAll(Allocation.USAGE_SCRIPT);
allocationCount.copyTo(count);

// The count can now be accessed via
count[0];