Improve a cmake variable doc string.

diff --git a/cmake/setup_cached_variables.cmake b/cmake/setup_cached_variables.cmake
index 788e68a826f35d3f3a3408b7c23e43c09d85759b..b3fc8b9e5dbc266ed7309a9904c09f0500804884 100644 (file)
--- a/cmake/setup_cached_variables.cmake
+++ b/cmake/setup_cached_variables.cmake
@@ -154,7 +154,7 @@ set(CMAKE_CONFIGURATION_TYPES "${CMAKE_BUILD_TYPE}")
 #
 
 option(DEAL_II_ALLOW_PLATFORM_INTROSPECTION
-  "Allow platform introspection for CPU command sets, SSE and AVX"
+  "Allow platform introspection, i.e., allow the compiler to query the CPU instruction set available on the current machine (e.g., whether the CPU supports the SSE or AVX vector instructions) and to compile for that instruction set. This generally results in faster code, but code that may not run on other machines (including, for example, machines that may use the same file system on which you are working, but have an older CPU architecture)."
   ON
   )
 mark_as_advanced(DEAL_II_ALLOW_PLATFORM_INTROSPECTION)