InnerProduct possible BUG: 1.0 - sum(x * y). In faiss and milvus, its just sum(x * y)

[Arthur-Bi]

The original code is 6e829d1
which is 1.0 - sum(-1 * x * y)

Then in a9a2cd5
Code is changed to 1.0 - sum(x * y)

**Q1: why is -1 deleted in second commit? **

Q2: why is 1.0 - sum(-1 * x * y) in the original code? Because I checked the IP in milvus and faiss, it's just sum(x * y)

Faiss

FAISS_PRAGMA_IMPRECISE_FUNCTION_BEGIN
float fvec_inner_product(const float* x, const float* y, size_t d) {
    float res = 0.F;
    FAISS_PRAGMA_IMPRECISE_LOOP
    for (size_t i = 0; i != d; ++i) {
        res += x[i] * y[i];
    }
    return res;
}

Milvus

func IPImplPure(a []float32, b []float32) float32 {
	var sum float32

	for i := range a {
		sum += a[i] * b[i]
	}

	return sum
}

[guoxiangCN]

Hello, i also have the same question Q2 ? can you explain it ? maybe the inner product is designed for l2 norm to calac cosine ?