fix matrix memory failures

Will Kimmerer · Will Kimmerer · commit e43098e986ab · 2022-03-03T23:57:26.000-05:00
diff --git a/src/chainrules/utilityrules.jl b/src/chainrules/utilityrules.jl
@@ -0,0 +1,5 @@
+function rrule(::typeof(build), I::AbstractVector, J::AbstractVector, J::AbstractVector, m, n, combine::typeof(+))
+    project_V = ProjectTo(V)
+    function sparse_pullback(ΔΩ)
+        ΔΩ = unthunk(ΔΩ)
+        ΔV = project_V()
