[Bug report] `dr::scatter` for Quaternion seems to be incorrect

[Chaphlagical]

Hi, I try following code for setting quaternion data:

using Float = dr::LLVMArray<float>;

int main()
{
	jit_init(JitBackend::LLVM);

	dr::Array<Float, 3> x = dr::zeros<dr::Array<Float, 3>>(3);
	dr::scatter(x, dr::Array<Float, 3>(1, 2, 3), 0);
	dr::scatter(x, dr::Array<Float, 3>(11, 12, 13), 1);
	dr::scatter(x, dr::Array<Float, 3>(21, 22, 23), 2);

	dr::Quaternion<Float> y = dr::zeros<dr::Quaternion<Float>>(3);
	dr::scatter(y, dr::Quaternion<Float>(1, 2, 3, 4), 0);
	dr::scatter(y, dr::Quaternion<Float>(11, 12, 13, 14), 1);
	dr::scatter(y, dr::Quaternion<Float>(21, 22, 23, 24), 2);

	std::cout << x << std::endl;
	std::cout << y << std::endl;

        return 0;
}

Output:

[[1, 2, 3],
 [11, 12, 13],
 [21, 22, 23]]
[4 + 21i + 22j + 23k,
 14 + 0i + 0j + 0k,
 24 + 0i + 0j + 0k]

However,

[4 + 1i + 2j + 3k,
 14 + 11i + 12j + 13k,
 24 + 21i + 22j + 23k]

is what I expected.

Is it a Dr.JIT bug or just I didn't do it right?

[njroussel]

Hi @Chaphlagical

This sounds like a Dr.Jit bug, and I can only reproduce it in C++. In Python it works fine, it produces the result that you expected. I'll look into this.

[njroussel]

I have pushed a fix to master: 9a7ac4e

Thank you for reporting this issue 😄

[Chaphlagical]

Thanks!