Backward Gradients

\begin{nskFigure}[]
	\foreach \v[count=\i] in {r, s, t} {
			\nskBlock[
				type=circle, width=1cm, id=d\v,
				text-center={\large$\frac{\partial{z}}{\partial{\v}}$},
				text-north=\i, last-pos-s={right=.5cm}, text-north-style={xshift=-3mm}
			]
		}
	\nskBlock[id=gc, text-center={grad\_fn \textbf{C}}, pos={below=of \nskID!{2}}, fill=nskOrange]
	\nskBlock[id=ga, text-center={grad\_fn \textbf{A}}, last-pos={above left=3cm and 0cm}, fill=nskMainAccent]
	\nskBlock[id=gb, text-center={grad\_fn \textbf{B}}, last-pos={right=2.5cm}, fill=nskSecondaryAccent]
 
	\nskBlock[
		type=circle, width=1cm, id=dx,
		text-center={\large$\frac{\partial{z}}{\partial{x}}$},
		pos={above=of ga}, fill=nskMainAccent,
	]
	\nskBlock[
		type=circle, width=1cm, id=dy,
		text-center={\large$\frac{\partial{z}}{\partial{y}}$},
		pos={above=of gb},  fill=nskSecondaryAccent,
	]
 
	\foreach \v in {r, s, t} {\nskConnect[from=gc, to=d\v, bend-type=double]}
	\nskConnect[from=dr, to=ga, bend-type=double]
	\foreach \v in {s, t} {\nskConnect[from=d\v, to=gb, bend-type=double]}
	\foreach \f/\t in {a/x, b/y} {\nskConnect[from=g\f, to=d\t]}
 
	% annotations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <<<
	\nskAnnotate[
		connect-to=dy, pos={right=2.7cm of dy}, anchor-from=west,
		header={Leaf Nodes}, title={AccumulateGrad},
		text=Leaf nodes,
		fill=none, border-type=none,
	]
	\nskMeasure[from=gb.east, to=\nskID{1}.west]
	\nskAnnotate[
		connect-to=gb, pos={right=\nskDistance of gb}, anchor-from=west,
		header={Dependencies}, title={Decrement \& Dispatch},
		text={Dec. deps, queue if ready.},
		fill=none, border-type=none,
	]
	\nskMeasure[from=gc.east, to=\nskID{1}.west]
	\nskAnnotate[
		connect-to=gc, pos={right=\nskDistance of gc}, anchor-from=west,
		header=Outputs, title=Grad Mapping, text=One grad per input.,
		fill=none, border-type=none,
	]
 
\end{nskFigure}
]