Should it be B' and A' in the C' equation?

Is this an example of where the "fused multiply and add" operation I've heard of would be of use on a GPU?

@harrysha1029,i have same question with you,I think here B and A suppose be premultiplied(B', A').

@dragonite As far as I know, lots of operations in GPU is matrix multiplication (like we already saw in some of the transform and other Compute related application). The basic of matrix multiplication is multiply-add. To accelerate this, hardware usually makes fused multiply–accumulate (FMAC) as efficient as possible (Power/Area). I guess this is what you refer as multiply and add.

Is the only benefit of pre-multiplied alpha easier calculations when calculating the alpha blending for the relevant color? Or are there other kinds of computational benefits, because wouldn't it be computationally taxing to also pre-compute all the alphas in the first place?

So are both the premultiplied and the composite approaches the same?

@sman64 I would say that they're the same in what they intend to accomplish (i.e. they are essentially the same formula and the same math), but they achieve it differently. If we represent all colors as defined in A,B,C then we would have to perform more compute at runtime than if we chose to represent color as premultiplied A',B',C'

Good for reference for solving Exercise 4 problem 1