From cff929a08301e4d791de55fd3a9f86e38dbf56ad Mon Sep 17 00:00:00 2001
From: NiccoloN <niccolo.nicolosi@gmail.com>
Date: Thu, 23 Apr 2026 10:34:29 +0200
Subject: [PATCH] fix sigmoid implementation stability in pim-simulator

---
 .../src/lib/memory_manager/type_traits.rs        | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/backend-simulators/pim/pim-simulator/src/lib/memory_manager/type_traits.rs b/backend-simulators/pim/pim-simulator/src/lib/memory_manager/type_traits.rs
index 6778dfa..b79d51d 100644
--- a/backend-simulators/pim/pim-simulator/src/lib/memory_manager/type_traits.rs
+++ b/backend-simulators/pim/pim-simulator/src/lib/memory_manager/type_traits.rs
@@ -55,15 +55,23 @@ pub trait HasSigm {
 
 impl HasSigm for f32 {
     fn sigm(self) -> Self {
-        let ex = self.exp();
-        ex / (1.0 + ex)
+        if self >= 0.0 {
+            1.0 / (1.0 + (-self).exp())
+        } else {
+            let ex = self.exp();
+            ex / (1.0 + ex)
+        }
     }
 }
 
 impl HasSigm for f64 {
     fn sigm(self) -> Self {
-        let ex = self.exp();
-        ex / (1.0 + ex)
+        if self >= 0.0 {
+            1.0 / (1.0 + (-self).exp())
+        } else {
+            let ex = self.exp();
+            ex / (1.0 + ex)
+        }
     }
 }