Different result in Burst VS CSharp Compiler

Unity Engine
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1 
int bb = BurstMethod(2 * Mathf.PI); // =2048
int cc = CsharpMethod(2 * Mathf.PI); // =2047

    [BurstCompile]
    static int BurstMethod(float b)
    {
        const float a = 1024f / Mathf.PI;
        return (int)(b * a);
    }
    static int CsharpMethod(float b)
    {
        const float a = 1024f / Mathf.PI;
        return (int)(b * a);
    }
2

Hi, this is expected behavior. Internally mono promotes all floating-point number operations to double precision and then converts it back down into single-precision (float) when storing it. While Burst does all the calculations as single-precision as you’d expect when working with float types. This is the same behavior you’d get from equivalent C/C++ code or from CoreCLR.