Merge pull request #1373 from dcbdan/master

 Modifying parallel search algorithm for zero length searches

hpx/parallel/algorithms/search.hpp

@@ -66,7 +66,7 @@ namespace hpx {namespace parallel { HPX_INLINE_NAMESPACE(v1)
 
                 s_difference_type diff = std::distance(s_first, s_last);
                 if (diff <= 0)
-                    return result::get(std::move(last));
+                    return result::get(std::move(first));
 
                 difference_type count = std::distance(first, last);
                 if (diff > count)

tests/regressions/CMakeLists.txt

@@ -14,6 +14,7 @@ set(subdirs
     threads
     traits
     util
+    parallel
    )
 
 if(HPX_HAVE_CXX11_LAMBDAS)

tests/regressions/parallel/CMakeLists.txt

@@ -5,6 +5,7 @@
 
 set(tests
     minimal_findend
+    search_zerolength
    )
 
 foreach(test ${tests})

tests/regressions/parallel/search_zerolength.cpp

@@ -0,0 +1,50 @@
+//  Copyright (c) 2015 Daniel Bourgeois
+//
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <hpx/hpx_init.hpp>
+#include <hpx/hpx.hpp>
+#include <hpx/include/parallel_search.hpp>
+#include <hpx/util/lightweight_test.hpp>
+
+void search_zero_dist_test()
+{
+    using hpx::parallel::execution_policy;
+    using hpx::parallel::seq;
+    using hpx::parallel::par;
+    using hpx::parallel::search;
+    using hpx::parallel::task;
+
+    typedef std::vector<int>::iterator iterator;
+
+    std::vector<int> c(10007);
+    std::iota(c.begin(), c.end(), 1);
+    std::vector<int> h(0);
+
+    hpx::future<iterator> fut_seq = search(seq(task), c.begin(), c.end(),
+        h.begin(), h.end());
+    hpx::future<iterator> fut_par = search(par(task), c.begin(), c.end(),
+        h.begin(), h.end());
+
+    HPX_TEST(fut_seq.get() == c.begin());
+    HPX_TEST(fut_par.get() == c.begin());
+}
+
+int hpx_main()
+{
+    search_zero_dist_test();
+    return hpx::finalize();
+}
+
+int main(int argc, char* argv[])
+{
+    std::vector<std::string> cfg;
+    cfg.push_back("hpx.os_threads=" + boost::lexical_cast<std::string>
+                  (hpx::threads::hardware_concurrency()));
+
+    HPX_TEST_EQ_MSG(hpx::init(argc, argv, cfg), 0,
+        "HPX main exted with non-zero status");
+
+    return hpx::util::report_errors();
+}