From b4113475f2c39f4e599cbf83fc5acc33c178cb43 Mon Sep 17 00:00:00 2001
From: Chin-Chang Yang <2770271+ChinChangYang@users.noreply.github.com>
Date: Tue, 4 Nov 2025 11:45:46 +0800
Subject: [PATCH] Reduce mish error by an alternative without softplus op

---
 coremltools/converters/mil/frontend/torch/ops.py | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/coremltools/converters/mil/frontend/torch/ops.py b/coremltools/converters/mil/frontend/torch/ops.py
index 8691dd93d..0bab71830 100644
--- a/coremltools/converters/mil/frontend/torch/ops.py
+++ b/coremltools/converters/mil/frontend/torch/ops.py
@@ -1803,9 +1803,15 @@ def mish(context, node):
     inputs = _get_inputs(context, node, expected=1)
     x = inputs[0]
 
-    softplus = mb.softplus(x=x)
-    tanh = mb.tanh(x=softplus)
-    res = mb.mul(x=x, y=tanh, name=node.name)
+    # e = exp(x)
+    # mish = x / (1 + 2 / (e * (e + 2)))
+    e = mb.exp(x=x)
+    ep2 = mb.add(x=e, y=2.0)
+    emep2 = mb.mul(x=e, y=ep2)
+    tdemep2 = mb.real_div(x=2.0, y=emep2)
+    optdemep2 = mb.add(x=1.0, y=tdemep2)
+    res = mb.real_div(x=x, y=optdemep2, name=node.name)
+
     context.add(res)