From 01117b10ffa027423906cd7bf801b24d3be92ca2 Mon Sep 17 00:00:00 2001
From: Kalin Kiesling <krkiesling@gmail.com>
Date: Tue, 15 Mar 2022 10:43:22 -0500
Subject: [PATCH] use xtensor library on system if it already exists, else use
 vendored submodule

---
 CMakeLists.txt | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a01d02fb3..1e514e32b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -71,7 +71,12 @@ if(pugixml_FOUND)
 else()
   message(STATUS "Did not find pugixml, will use submodule instead")
 endif()
-
+find_package(xtensor QUIET NO_SYSTEM_ENVIRONMENT_PATH)
+if(xtensor_FOUND)
+  message(STATUS "Found xtensor: ${xtensor_DIR} (version ${xtensor_VERSION})")
+else()
+  message(STATUS "Did not find xtensor, will use submodule instead")
+endif()
 #===============================================================================
 # libMesh Unstructured Mesh Support
 #===============================================================================
@@ -211,9 +216,11 @@ if (NOT (CMAKE_VERSION VERSION_LESS 3.13))
   cmake_policy(SET CMP0079 NEW)
 endif()
 
-add_subdirectory(vendor/xtl)
-set(xtl_DIR ${CMAKE_CURRENT_BINARY_DIR}/vendor/xtl)
-add_subdirectory(vendor/xtensor)
+if (NOT xtensor_FOUND)
+  add_subdirectory(vendor/xtl)
+  set(xtl_DIR ${CMAKE_CURRENT_BINARY_DIR}/vendor/xtl)
+  add_subdirectory(vendor/xtensor)
+endif()
 
 #===============================================================================
 # GSL header-only library