[Flutter] Flutter compute function takes time to start execute

I am trying to use Flutters compute function to do some real time heavy image processing using a C++ code and dart ffi.
I tried wrapping the call to the heavy function in a compute to avoid messing with the ui thread and I took some time measurements to see what takes the most time to execute.

the code looks like this:

double _work(CheckPhotoData p) {
DateTime s = DateTime.now();
Pointer<Double> rPointer = Pointer.fromAddress(p.rPointerAddress);
Pointer<Double> gPointer = Pointer.fromAddress(p.gPointerAddress);
Pointer<Double> bPointer = Pointer.fromAddress(p.bPointerAddress);
final a = NativeCCode.checkPhoto(rPointer, gPointer, bPointer, p.w, 1);
print("ACTUAL NativeCCode.checkPhoto took: " + DateTime.now().difference(s).inMilliseconds.toString());
return a;
}

class CheckPhotoWrapper {
static Future<double> checkPhotoWrapper(Uint8List photo) async {
final CheckPhotoData deconstructData = _deconstructData(photo);
DateTime s = DateTime.now();
double res = await compute(_work, deconstructData);
print("compute took: " + DateTime.now().difference(s).inMilliseconds.toString());
return res;
}
...
}


After running the code I got this output:

ACTUAL NativeCCode.checkPhoto took: 106
compute took: 514
​

(this means that compute took 408ms more than the code it runs)

From what I understand from these results, the actual compute method from dart:async is taking much more time then the actual code its executing and causes a big overhead impacting the performance.
Even worse, my app UI is stuck when the processing starts.

Is there a way to reduce the overhead that compute introduces or a different approach this issue that I couldn't figure out?

Thanks for any idea or a solution to my problem.

Note:

• I ran the test on debug mode on a physical device.
• CheckPhotoData is a simple class containing the parameters to my _work function.
• I am using flutter version 2.2.3, Channel stable

Continue reading...