Function dot 

pub fn dot<A, B, R, OpA, OpB>(
    a: &StridedView<'_, A, OpA>,
    b: &StridedView<'_, B, OpB>,
) -> Result<R>
where
    A: Copy + Mul<B, Output = R> + MaybeSendSync + 'static,
    B: Copy + MaybeSendSync + 'static,
    R: Copy + Zero + Add<Output = R> + MaybeSendSync + MaybeSimdOps + 'static,
    OpA: ElementOp<A>,
    OpB: ElementOp<B>,

Dot product: sum(OpA::apply(a[i]) * OpB::apply(b[i])).

Operands may have different element types. Result type R must be A * B. SIMD fast path fires only when A == B == R (same type) and both Identity ops.