From 8ce341caf2947e4b5ac4580c20254ae7d828b009 Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Wed, 11 Aug 2021 18:10:01 +0000
Subject: [PATCH] * revise the meta_least_common_multiple function template,
 add a bool variable to check whether the A is larger than B. * This can make
 less compile_time if A is smaller than B. and avoid failure in compile if we
 get a little A and a great B.

Authored by @awoniu.
---
 Eigen/src/Core/util/Meta.h | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index 2429ddad2..81ae2a32d 100755
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -715,20 +715,25 @@ class meta_sqrt<Y, InfX, SupX, true> { public:  enum { ret = (SupX*SupX <= Y) ?
 
 
 /** \internal Computes the least common multiple of two positive integer A and B
-  * at compile-time. It implements a naive algorithm testing all multiples of A.
-  * It thus works better if A>=B.
+  * at compile-time. 
   */
-template<int A, int B, int K=1, bool Done = ((A*K)%B)==0>
+template<int A, int B, int K=1, bool Done = ((A*K)%B)==0, bool Big=(A>=B)>
 struct meta_least_common_multiple
 {
   enum { ret = meta_least_common_multiple<A,B,K+1>::ret };
 };
+template<int A, int B, int K, bool Done>
+struct meta_least_common_multiple<A,B,K,Done,false>
+{
+  enum { ret = meta_least_common_multiple<B,A,K>::ret };
+};
 template<int A, int B, int K>
-struct meta_least_common_multiple<A,B,K,true>
+struct meta_least_common_multiple<A,B,K,true,true>
 {
   enum { ret = A*K };
 };
 
+
 /** \internal determines whether the product of two numeric types is allowed and what the return type is */
 template<typename T, typename U> struct scalar_product_traits
 {