+function DAG:computeGradOutput(gradInputSucc)
+ local gi
+ if #gradInputSucc == 1 then
+ gi = gradInputSucc[1] -- we avoid a clone()
+ elseif #gradInputSucc > 1 then
+ for k = 1, #gradInputSucc do
+ if gi then
+ gi:add(gradInputSucc[k])
+ else
+ gi = gradInputSucc[k]:clone()
+ end
+ end
+ end
+ return gi
+end
+