From 74f11ea9d8a4978fbbaa9a5e61a6d71bd2f0a448 Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Sun, 28 Jul 2024 09:50:01 -0400
Subject: [PATCH] Default preference for MKL checks if Ryzen

---
 src/LinearSolve.jl | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/LinearSolve.jl b/src/LinearSolve.jl
index 894c6e0d..d195a69d 100644
--- a/src/LinearSolve.jl
+++ b/src/LinearSolve.jl
@@ -44,7 +44,16 @@ import PrecompileTools
 
 const CRC = ChainRulesCore
 
-if Preferences.@load_preference("LoadMKL_JLL", true)
+# Check if Ryzen, since that's where MKL is slow
+function is_zen()
+   # znverX
+   n = Sys.CPU_NAME
+   length(n) == 6 || return false
+   return n[1] == 'z' && n[2] == 'n' && n[3] == 'v' &&
+      n[4] == 'e' && n[5] == 'r'
+end
+
+@static if Preferences.@load_preference("LoadMKL_JLL", is_zen())
     using MKL_jll
     const usemkl = MKL_jll.is_available()
 else