From 053984e2a2358769fe9665c8d20475de5d223ddf Mon Sep 17 00:00:00 2001
From: Corey Lowman <clowman1993@gmail.com>
Date: Wed, 20 Jul 2022 16:53:30 -0400
Subject: [PATCH] Changing dropout to use map_df_uses_fx

---
 src/tensor_ops/impl_dropout.rs | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/src/tensor_ops/impl_dropout.rs b/src/tensor_ops/impl_dropout.rs
index 85d816df9..94fb3e353 100644
--- a/src/tensor_ops/impl_dropout.rs
+++ b/src/tensor_ops/impl_dropout.rs
@@ -1,7 +1,6 @@
-use super::utils::move_tape_and_add_backward_op;
 use crate::prelude::*;
 use rand::Rng;
-use rand_distr::{Distribution, Standard};
+use rand_distr::Standard;
 
 /// Randomly drops out elements from `t` with probability `p`, and multiplies all elements by `1 / (1 - p)`.
 ///
@@ -15,17 +14,17 @@ pub fn dropout<T: Tensor<Dtype = f32>, R: Rng>(t: T, p: f32, rng: &mut R) -> T {
     } else {
         // `t` owns the tape in this branch, so apply dropout randomly.
         let rinvp = (1.0 - p).recip();
-        let deriv = T::Device::filled(&mut |d| {
-            let val: f32 = Standard.sample(rng);
-            *d = if val < p { 0.0 } else { rinvp };
-        });
-        let mut result = T::NoTape::zeros();
-        T::Device::addmul(result.mut_data(), t.data(), deriv.as_ref());
-
-        move_tape_and_add_backward_op(t, result, move |t, result, grads| {
-            let (t_grad, result_grad) = grads.mut_and_ref(&t, &result);
-            T::Device::addmul(t_grad, deriv.as_ref(), result_grad);
-        })
+        map_df_uses_fx(
+            t,
+            move |x| {
+                if rng.sample::<f32, Standard>(Standard) < p {
+                    0.0
+                } else {
+                    x * rinvp
+                }
+            },
+            move |fx| if fx > &0.0 { rinvp } else { 0.0 },
+        )
     }
 }