Add reset!(), comment out wrong rules

README.md

@@ -43,6 +43,13 @@ for i=1:100
 end
 ```
 
+Note that Yota caches gradients and may not see changes to functions
+if you redefine them (e.g. in REPL). To reset the cache, invoke:
+
+```julia
+Yota.reset!()
+```
+
 
 ## ChainRules
 

src/drules.jl

@@ -92,15 +92,16 @@ end
 
 # some special broadcasting rules
 
-function ∇broadcasted(dy, ::typeof(Broadcast.broadcasted), f::typeof(+), args...)
- return NoTangent(), NoTangent(), [dy for a in args]...
-end
-@drule Broadcast.broadcasted(f::typeof(+), args::Vararg) ∇broadcasted
+# are these rules just incorrect versions of the `∇broadcasted_special` below?
+# function ∇broadcasted(dy, ::typeof(Broadcast.broadcasted), f::typeof(+), args...)
+# return NoTangent(), NoTangent(), [dy for a in args]...
+# end
+# @drule Broadcast.broadcasted(f::typeof(+), args::Vararg) ∇broadcasted
 
-function ∇broadcasted(dy, ::typeof(Broadcast.broadcasted), f::typeof(*), args...)
- return NoTangent(), NoTangent(), [dy .* a for a in args]...
-end
-@drule Broadcast.broadcasted(f::typeof(*), args::Vararg) ∇broadcasted
+# function ∇broadcasted(dy, ::typeof(Broadcast.broadcasted), f::typeof(*), args...)
+#  return NoTangent(), NoTangent(), [dy .* a for a in args]...
+# end
+# @drule Broadcast.broadcasted(f::typeof(*), args::Vararg) ∇broadcasted
 
 # @diffrule getindex(u::AbstractArray, i) u ungetindex(u, dy, i)
 

src/grad.jl

@@ -107,8 +107,6 @@ end
 Make a single step of backpropagation.
 """
 function step_back!(tape::Tape, y::Variable, deriv_todo::Vector{Variable})
- # TODO: here's the problem with the constructor_loss test:
- # we reach y = __new__(...) twice and update all its fields twice
  @debug "step_back!() for $(tape[y])"
  df = get_deriv_function(call_signature(tape, tape[y]))
  dy = tape.c.derivs[y]
@@ -234,6 +232,8 @@ end
 
 const GRAD_CACHE = Dict{Any,Any}()
 
+reset!() = empty!(GRAD_CACHE)
+
 
 """
  grad(f, args...; seed=1)