Author Archives: terboven

OpenMP 4.5 is on its way

Last week the first ever OpenMPCon and the IWOMP 2015 workshops took place here in Aachen and this week we hosted the OpenMP Language Committee face-to-face meeting. An important goal of this meeting was to address the remaining open issues and then to complete the specification work to make the next version of OpenMP available in time for SC15. The OpenMP 4.1 draft was released in July this year and the comment period was open until the end of September. However, after realizing how many changes and particularly improvements this next version will bring, we decided that we want to call it OpenMP 4.5. Keeping the major version at “4” assures that the changes will not break any existing code.

Within the next few weeks the Language Committee will make the final changes to the spec text and a final verification run, then the document will be handed over to the OpenMP Architecture Review Board (ARB) for the voting. It can be expected that the ARB will accept the document as the new version of the OpenMP standard. It will then be released early at SC15. If you like to know what it is and talk to us, come to our tutorial on Advanced OpenMP Programming on the Monday right before SC15.

Actually the number of changes is large, about 130 tickets have been passed. Any change to the spec text is represented by a ticket capturing the changes in LaTeX code and of course the corresponding discussion(s). However, there are tickets of different size: some are small and contain only minor corrections, others are large and bring lots of new functionality (I think the target stuff of OpenMP 4.0 was captured in two huge tickets).

OpenMP 4.5 will obviously bring many clarifications and some minor corrections, but also some notable enhancements:

  • We handled several items from the Fortran 2003 todo list. Fortran 2003 is now supported as a base language with a few exceptions mentioned explicitly.
  • SIMD and Tasking extensions and refinements made its way into OpenMP 4.5.
  • Finally, OpenMP will support reductions for C/C++ arrays and templates.
  • Runtime routines to support cancellation and affinity have been added.

We also introduced some new features:

  • Support for doacross loops.
  • Loops can now be divided into tasks with the taskloop construct.

I plan to talk about some of these here in detail.

At IWOMP, Bronis de Supinski from LLNL, who is the Chair of the OpenMP Language Committee, gave a talk on the State of OpenMP & Outlook on OpenMP 4.1 (back then we did not had decided to call it 4.5). We will make all the IWOMP talks available on the IWOMP homepage soon, but here are two of his slides outlining the most important new additions above from what I mentioned already:

Bronis: OpenMP 4.1 Features (1/2)

Bronis: OpenMP 4.1 Features (1/2)

Bronis: OpenMP 4.1 Features (2/2)

Bronis: OpenMP 4.1 Features (2/2)

During his talk he also outlined what is on the agenda for OpenMP 5.0:

Bronis: OpenMP 5.0 Plans

Bronis: OpenMP 5.0 Plans

SC14 Video: A Short Stroll Through OpenMP 4.0

During SC14, Michael Klemm from Intel and myself teamed up to give an OpenMP 4.0 overview talk at the OpenMP booth. Our goal was to touch on all important aspects, from thread binding over tasking to accelerator support, and to entertain our audience in doing so. Although not all jokes translate from German to English as we intended, I absolutely think that the resulting video is a fun-oriented 25-minutes run-down of OpenMP 4.0 and worth sharing here:

OpenMP Timeline

At the OpenMP BoF Session during SC14, James Cownie from Intel showed an OpenMP Timeline which I thought interesting enough to share. It displays the release history of OpenMP and summarizes the major new features. It also shows the growing number of institutions belonging to the OpenMP standard.

The document was originally created for the Intel Parallel Universe magazine and has been released as open source :-) at the homepage of the Intel Open Source OpenMP Runtime: If you are like me and not well-versed in handling Adobe Illustrator or SVG file formats, you may use this PDF which has been created from the version released in September 2014.

OpenMP Timeline (PNG format)

OpenMP Timeline (PNG format)

Here is the link to the PDF: OpenMP Timeline.

Upcoming OpenMP Tutorials

This blog post is to announce three OpenMP tutorial events that I have committed to. As usual, my OpenMP tutorials focus on Tasking early on and when it comes to performance, I will talk about dealing with NUMA architectures and thread + data affinity in detail. So if you are interested in learning more about these topics and in getting hands-on experience, the tutorials might be of interest for you.

The first one is in about two weeks from now at the Hartree Centre in the UK and part of the Hartree Summer School Series 2014. This summer school consists of three weeks in total, of which the first one is dedicated to Visualization, the second one to High Performance Computing (HPC) and the last and third week is all about Big Data. The week on HPC covers all the HPC programming foundations you might need (I would say), including my part on OpenMP.

The second tutorial event is in September as part of the IWOMP 2014 workshop in Salvador in Brazil. This year’s IWOMP will host two tutorials, the first one is a full-day Introduction to OpenMP given by my colleague Dirk Schmidl and myself. We will do an experiment this year in that we partition the tutorial into many small parts of roughly 20 minutes per topic. During these short slots we will present a specific topic, and each slot will directly be followed by practical hands-on exercises or live demos on the given topic. The second tutorial at IWOMP 2015 2014 will be a half-day tutorial on the OpenMP Accelerator Model given by Eric Stotzer. The plan is that attendees can decide for their specialization: we teach the basics in the morning and go into performance tuning for “traditional” architectures in the afternoon, while Eric will cover the target construct in detail in the afternoon.

Finally the third tutorial will be at SC14 in New Orleans in November, as our Advanced OpenMP Tutorial has been accepted again. This tutorial is really about advanced OpenMP programming for performance, as we want to enable an in-depth understanding of advanced OpenMP constructs and features to provide attendees with a set of performance and scalability recipes that can be applied to improve performance of OpenMP applications. We will also explain how to write new code for and extend existing OpenMP code to compute accelerators with the new OpenMP 4.0 capabilities and in order to do so we extended the team of previous years (consisting of Bronis R. de Supinski, Michael Klemm, Ruud van der Pas and myself) with Eric Stotzer to cover this aspect in detail.

PPCES Video Lectures on OpenMP, MPI and Xeon Phi release

Since 2001 already, the IT Center (formerly: Center for Computing and Communication) of RWTH Aachen University offers a one week HPC workshop on Parallel Programming during spring time. This course is not restricted to scientists and engineers from our university, in fact we have about 30% of external attendees each time. This year we were very happy about a record attendance of up to 85 persons for the OpenMP lectures on Wednesday. As usual we publish all course materials online, but this year we also created screencasts from all presentations. That means you see the slides and the live demos and you hear the presenter talk. This blog post contains links to both the screencasts as well as the other course material, sorted by topic.


We have three talks as an introduction to OpenMP from Wednesday and two talks on selected topics from Thursday, which were vectorization and tools.

Introduction to OpenMP Programming (part 1), by Christian Terboven:


Getting OpenMP up to Speed, by Ruud van der Pas:


Introduction to OpenMP Programming (part 2), by Christian Terboven:


Vectorization with OpenMP, by Dirk Schmidl:


Tools for OpenMP Programming, by Dirk Schmidl:



We have two talks as an introduction to MPI and one on using the Vampir toolchain, all from Tuesday.

Introduction to MPI Programming (part 1), by Hristo Iliev:


Introduction to MPI Programming (part 2), by Hristo Iliev:


Introduction to VampirTrace and Vampir by Hristo Iliev:


Intel Xeon Phi

We put a special focus on presenting this architecture and we have one overview talk and one talk on using OpenMP 4.0 constructs for this architecture.

Programming the Intel Xeon Phi Coprocessor Overview, by Tim Cramer:


OpenMP 4.0 for Accelerators, by Christian Terboven:


Other talks

Some more talks, for instance on using our cluster or basics of parallel computer architectures, can be found in the youtube channel:

New article on OpenMP 4.0 online

A while ago I published a list with articles and tutorials on OpenMP 4.0, including the German article on heise Developer I wrote together with Michael Klemm (Intel). A slightly modified English version of our text now appeared in issue 16 of Intel’s Parallel Universe magazine, titled Full throttle: OpenMP 4.0.

The current issue and also past issues of the Parallel Universe magazine are available at If you are interested in developing parallel code for Intel architectures you might find some interesting reads over there.