sqrt(0.0) sometimes, but only sometimes, returns NaN

[ipr-fredrik2]

Expected behaviour: sqrt(0.0) == 0.0

Actual behaviour: Sometimes sqrt(0.0) == 0.0, but also sometimes sqrt(0.0).isNaN

Can be tested by simply evaluating this a bunch of times, and print or breakpoint or whatever if its true sqrt(0.0).isNaN

From math.dart

Dart SDK version: 3.5.3 (stable) (Wed Sep 11 16:22:47 2024 +0000) on "windows_x64"

[dart-github-bot]

Summary: The sqrt(0.0) function inconsistently returns either 0.0 or NaN. This behavior is observed when repeatedly evaluating the function, suggesting a potential issue with the implementation or underlying floating-point operations.

[julemand101]

What platform are you running the program on? (web? compiled? jit?). Can you post an example program which you have used to reproduce the issue? (I have tried a few times but can't reproduce it).

[a-siva]

@ipr-fredrik2 can you provide repro instructions as mentioned in the comment above.

[ipr-fredrik2]

I ran the application on Android yesterday in debug mode when I produced the issue, using a breakpoint + log message in an if statement. I was able to trigger the issue several times, fully restarting the application in between.

I can't seem to be able to reproduce this today for whatever reason, neither in my actual application or in a minimal repro. I have no idea what happened. I've restarted my equipment since then, maybe hardware issue or something else weird?

I can come back to this thread if I manage to trigger it again, feel free to close this issue in the meantime.

Here's a minimal reproducable example that should in theory recreate the issue, given the same unknown circumstance that happened yesterday:

import 'package:flutter/material.dart';
import 'dart:math';
import 'dart:developer' as dev;

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  void _onPressed(){
    double gamma = 144.5; // fluff
    for(int i = 0; i < 1024; i++)
    {
      double alpha = 14 * i.toDouble(); // fluff
      double beta = alpha * gamma; // fluff
      if(sqrt(0.0).isNaN)
      {
        dev.log("(sqrt(0.0) was NaN), beta: $beta");
      }
    }

  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: TextButton(
            child: const Text('Hello World!'),
            onPressed: _onPressed
          ),
        ),
      ),
    );
  }
}

[julemand101]

@ipr-fredrik2

I ran the application on Android yesterday in debug mode when I produced the issue,

Just for the details, can you specify if you was running this in inside an emulator or physical device? Also, which CPU architecture was this running as?

[ipr-fredrik2]

Physical device, Samsung Tab Active 4 Pro (model number T636B), android-arm64

[a-siva]

Will mark this as P3 until we are able to reproduce the issue.

[a-siva]

//cc @alexmarkov