title: Can queries to boost's rtree be done from parallel threads?
body: <p>I have two modules in application. <strong>Module1</strong> owns and builds <code>boost::geometry::index::rtree</code>. <strong>Module2</strong> makes queries to <strong>Module1</strong>, which are passed to RTree. Now I want to speed up and have several <strong>Module2</strong> instances, which make queries to <strong>one Module1</strong> instance, and work separately. I am 100% sure, that while <strong>any Module2 working RTree does not change</strong>.</p>
  
  <p>I've found this question: <a href="https://stackoverflow.com/questions/28266656/can-i-use-boost-geometry-index-rtree-with-threads">Can I use Boost.Geometry.index.rtree with threads?</a>, but it describes more complicated case, when rtree is modified and queried from different threads. And this answer is ambiguous: "No boost Rtree is not thread-safe in any way" is stated in answer. But in comments it is stated: "It is safe to do queries, and it even possible to create workaround for creation". What is right answer? Are there any resources, except ask direct question to boost authors, to find out?</p>
  
  <p>Tl;dr:</p>
  
  <p>Is it safe to make queries to <code>boost::geometry::index::rtree</code> from different threads, if I am 100% sure, that no thread modifies RTree?</p>