Hot fix for equal algo

[MikeDvorskiy]

Summary

Hot fix for equal algo

[ldionne]

include/pstl/internal/glue_algorithm_impl.h

739

Please restore the space here.

739

Why are you removing the TODO?

750

What problem is this fixing? IIUC, before this patch, we would end up calling equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2) here and that would be a compiler error because __pstl::internal::pstl_equal() is not an iterator. Is that correct?

If so, this change should be accompanied by a test that goes through this code path.

[MikeDvorskiy]

include/pstl/internal/glue_algorithm_impl.h

750

No...
The fact is there is several version of std::equal..
In particular,
equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2...
and
equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2, _ForwardIterator2...
where each sequence has its own length.
So, the error was the code calls the first version with "first1, last1, __first2"

[MikeDvorskiy]

include/pstl/internal/glue_algorithm_impl.h

739

"Distance check" is a kind of optimization for random access iterators..
But for forward iterators it is a kind of overhead.. and we should keep TODO complete the fixing.

Furthermore, I've just noticed, in case of size equal, we call a serial version std::equal(first1, last1, first2, p);

Ok, I'll complete the fixing and update the patch.
(and extend the test coverage as well)

[ldionne]

include/pstl/internal/glue_algorithm_impl.h

739

Please fix this in a separate patch (I've already applied this one).

include/pstl/internal/glue_algorithm_impl.h

return std::equal(std::forward<_ExecutionPolicy>(__exec), __first1, __last1, __first2,
                       __pstl::internal::pstl_equal());
 }
 
 template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
 __pstl::internal::enable_if_execution_policy<_ExecutionPolicy, bool>
 equal(_ExecutionPolicy&& __exec, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
       _ForwardIterator2 __last2, _BinaryPredicate __p)
 {
-    //TODO: to get rid of "distance"
-    if (std::distance(__first1, __last1) == std::distance(__first2, __last2))
+    if(std::distance(__first1, __last1) == std::distance(__first2, __last2))
         return std::equal(__first1, __last1, __first2, __p);
-    else
-        return false;
+
 }
 
 template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2>
 __pstl::internal::enable_if_execution_policy<_ExecutionPolicy, bool>
 equal(_ExecutionPolicy&& __exec, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
       _ForwardIterator2 __last2)
 {
-    return equal(std::forward<_ExecutionPolicy>(__exec), __first1, __last1, __first2, __pstl::internal::pstl_equal());
+    return equal(std::forward<_ExecutionPolicy>(__exec), __first1, __last1, __first2, __last2, __pstl::internal::pstl_equal());
 }
 
 // [alg.move]
 template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2>
 __pstl::internal::enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
 move(_ExecutionPolicy&& __exec, _ForwardIterator1 __first, _ForwardIterator1 __last, _ForwardIterator2 __d_first)
 {
     using namespace __pstl;