Johannes Habichs Blog


21. March 2012

HIWI Positions available at RRZE’s HPC group

Johannes Habich, 08:00 Uhr in Allgemeines, HPC

Are you  a student at FAU or OHN and  interested in HPC? There are open HiWi positions in our group!


Current topics:


Just write an Email to hpc “at” and ask for our current research topics.




Status: Open ; Last update 21.03.2012

HIWI Positions available at RRZE’s HPC Group

Johannes Habich, 06:45 Uhr in Allgemeines, HPC, Windows HPC

Are you  a student at FAU or OHN and  interested in HPC? There are open HiWi positions in our group!


Current topics:


Just write an Email to hpc “at” and ask for our current research topics.


Status: Open ; Last update 21.03.2012

10. February 2012

Future of this Blog

Johannes Habich, 06:35 Uhr in Allgemeines, Contact, CUDA, Home, HPC, Parallel Computing MPI/OpenMP, PRACE, Publications, SKALB, Tools, Windows HPC

Please find new posts to this blog here:


There will be no more posts here

6. February 2012

GIT: DIFF working tree against some revision or branch

Johannes Habich, 07:13 Uhr in Tools

git diff  fw7e7f8wef8wef yourfile.c


Gives the changes between current working dir and revision  or branch: fw7e7f8wef8wef

31. January 2012

GIT: Tag particular commit

Johannes Habich, 14:20 Uhr in Tools

Simply use git tag as usual but provide a valid commit hash:


git tag -a v1.0  cc622186a7322713f0ee4df8d58a1adcfe2ffef6   -m”tag a particular commit”

22. December 2011

GETOPT for Windows

Johannes Habich, 11:47 Uhr in HPC, Tools, Windows HPC

The portability of programs between *nix und Windows is often limited not by the program itself but by certain helper tools. One of those is getopt which provides a fast and easy way to read in command line arguments.

Please find a windows version here:


You will find more other useful ports here as well.

16. December 2011

GIT: git show and git describe

Johannes Habich, 06:36 Uhr in Tools

You can easily have a look at a tag with

git show  mytag

Much more powerfull and showing you all sorts of realations between tags and commits is git describe:

25. November 2011

XFCE: Set volumen function keys

Johannes Habich, 06:46 Uhr in Allgemeines, Tools

Go to Settings > Keyboard > Shortcuts and add three shortcuts for your function keys. The commands should be:

amixer set Master 5%+

amixer set Master 5%-

amixer set Master toggle

This requires that the function keys are actually recognized by your system but have no command assigned till now

10. November 2011

VirtualBox: ResizeHD

Johannes Habich, 06:14 Uhr in Allgemeines, Tools

In general the following should work:

VBoxManage modifyhd MYHD.vdi –resize 20000


Were 20000 is more or less 20 GB.

If the command fails several reasons could be the cause.

  • The virtual disk is already larger. Till now you cannot shrink drives that way. Take a close look in the VM whether you already use that space actually. In Windows this information is under Computer Management –> Storage –> Disk Management
  • The virtual disk has the wrong type. Issue the command:

 VBoxManage showhdinfo MYHD.vdi

If the result is not:

Format variant: dynamic default

you have to migrate your disk to that dynamic system. Since this is the default container for newer versions you can simply clone your HD file and then enlarge the new one:

VBoxManage clonehd MYHD.vdi MYNEWHD.vdi

  • I did not encounter other errors, please comment if you have any problem and/or solution




8. November 2011

WINDOWS: Build Boost for Visual Studio 2010

Johannes Habich, 12:04 Uhr in HPC, Windows HPC


If you are using headers only libraries, then all you need to do is to unarchive the boost download and set up the environment variables. The instruction below set the environment variables for Visual Studio only, and not across the system as a whole. Note you only have to do it once.

  1. Unarchive the latest version of boost (1.47.0 as of writing) into a directory of your choice (e.g.C:\boost_1_47_0).
  2. Create a new empty project in Visual Studio.
  3. Open the Property Manager and expand one of the configuration for the platform of your choice.
  4. Select & right click Microsoft.Cpp.<Platform>.user, and select Properties to open the Property Page for edit.
  5. Select VC++ Directories on the left.
  6. Edit the Include Directories section to include the path to your boost source files.
  7. Repeat steps 3 – 6 for different platform of your choice if needed.

If you want to use the part of boost that require building, but none of the features that requires external dependencies, then building it is fairly simple.

  1. Unarchive the latest version of boost (1.47.0 as of writing) into a directory of your choice (e.g.C:\boost_1_47_0).
  2. Start the Visual Studio Command Prompt for the platform of your choice and navigate to where boost is.
  3. Run: bootstrap.bat to build b2.exe (previously named bjam).
  4. Run b2: (Win32) b2 --toolset=msvc-10.0 --build-type=complete stage ; (x64) b2 --toolset=msvc-10.0 --build-type=complete architecture=x86 address-model=64 stage. Go for a walk / watch a movie or 2 / ….
  5. Go through steps 2 – 6 from the set of instruction above to set the environment variables.
  6. Edit the Library Directories section to include the path to your boost libraries output. (The default for the example and instructions above would be C:\boost_1_47_0\stage\lib. Rename and move the directory first if you want to have x86 & x64 side by side (such as to<BOOST_PATH>\lib\x86 & <BOOST_PATH>\lib\x64).
  7. Repeat steps 2 – 6 for different platform of your choice if needed.
If you want both x64 & win32 side by side, add “–stagedir=lib/win32” and “–stagedir=lib/x64” to the respective builds

31. October 2011

Exchange 2010: Enable RPC over HTTPS: Outlook Anywhere

Johannes Habich, 19:36 Uhr in Allgemeines




In Exchange Management Console select Server Node and  Client Access.


In action pane hit Enable Outlook Anywhere.


Additionally you need to install the Feature RPC over HTTP Proxy of Win200 Server.

30. October 2011

EXCHANGE 2010: An error caused a change in the current set of domain controllers

Johannes Habich, 18:09 Uhr in Allgemeines



After some digging in the profile, I found out the following file, which seemed to be the cause of the problem:

c:\users\<specific user>\appdata\roaming\microsoft\mmc\Exchange Management Console


Rename or delete this file, restart the EX2010 EMC and all errors will be gone.





15. August 2011

Outlook 2010 HTML break blue citation line

Johannes Habich, 10:34 Uhr in Allgemeines

Coming from Outlook 2003 everyone knows that one can break the blue line marking the cited text  by entering a new text or at least with the common reverse indent button. This does no longer work for Outlook 2007 and 2010 as the blue line is now represented in some different way.

You can get around this by Ctrl+Q but  if you check the email at the recipients mailbox, you will see the unbroken blue line again.

If you switch to Rich Text you can actually use Ctrl+Q and it will be that way at the recipients side too.

If you have a real solution to the html problem, please comment!!!!


Please refrain from any unfeasible comments about the sense and non-sense of HTML mails. For that a lot of forums are available online to take that garbage!

11. August 2011

OpenCL programming

Johannes Habich, 08:20 Uhr in Allgemeines

OpenCL Kernels get compiled at execution time (Just in Time, JIT).
This means that any error inside the kernel is discovered at that time.
The error message I get till now are very silent about what the problem of the kernel is.
So there is just one method of commenting and uncommenting to get a kernel debugged just for compilation.

Intel however recently released it’s first beta version of OpenCL with a lot of tools.
As with early Parallel Studio, these tools are only available for Windows (in particular Win Vista + and Server 2008) and not for Linux.
Note, that the runtime for compiling and running OpenCL is available for Linux, Mac and Windows!

Included is the Intel OpenCL Offline Compiler where you can load your kernel and precompile it.
Here the error messages are much more helpfull (of course, helpfull in a way ordinary compiler messages are helpfull :-)).
Nevertheless, a great tool which makes daily programming a lot easier.


9. August 2011

OpenCL GPU computing tutorial

Johannes Habich, 14:45 Uhr in CUDA, HPC

Very nice tutorial with hands on about installation, setup and programming:

5. August 2011

NVIDIA CUDA disable/enable ECC , new commands

Johannes Habich, 07:50 Uhr in CUDA, HPC

In order to query ECC status in CUDA 4.0 (and hopefully the next versions), nvidia-smi works a little bit different:

nvidia-smi -q | grep -e"Ecc Mode" -e"Product" -A2

will give you a excerpt.
Just use nvidia-smi -q for full output

To enable ECC:

nvidia-smi -i 0 -e 1

To disable ECC:

nvidia-smi -i 0 -e 0

Where i is the GPU ID!

4. August 2011

TinyGPU upgrade to CUDA Toolkit 4.0

Johannes Habich, 07:07 Uhr in CUDA, HPC

All nodes of the TinyGPU Cluster is now on the current CUDA Toolkit 4.0 and the appropriate driver.

12. July 2011

GIT: Compare/Diff working directory against server/repository state

Johannes Habich, 11:53 Uhr in Tools

git fetch –> updates your local rep but not your working Dir
git diff … origin gives you the comparison

11. July 2011

GIT: Ignore File mode/right changes

Johannes Habich, 06:00 Uhr in Tools

If you have files or directories under git control and change the rights of them, git does recognize them as changed.
To force git to ignore these changes just execute the following.

git config core.filemode false

You can reenable that after all files have a new revision because of an actual change and are comitted in the new mode anyway.

28. June 2011

LIKWID: Installation Hint

Johannes Habich, 06:50 Uhr in Tools

If you set the likwid install path in and the last character is a slash, likwid-pin will not run with the following error message:

ERROR: object ‘~/helper/likwid-2.2-inst’ from LD_PRELOAD cannot be preloaded: ignored.

Delete the last slash and do
make clean && make && make install

and likwid-pin should work fine.

27. June 2011

GIT: Clone Repository with different branch than master

Johannes Habich, 07:52 Uhr in Tools

git clone newdir -b yourbranchname

21. June 2011

Disable Fermi Cache

Johannes Habich, 10:33 Uhr in CUDA, HPC

To disable Fermi L1 Cache in CUDA just compile with: -Xptxas -dlcm=cg

Any idea on how to do this with OpenCL?

20. June 2011

7th Erlangen International High-End-Computing Symposium

Johannes Habich, 15:23 Uhr in Allgemeines, HPC

Please note the upcoming 7th EIHECS on this weeks Friday 24th of June .

14. June 2011

GIT: Getting information about tags

Johannes Habich, 11:53 Uhr in Tools

To show the tags you made and the comments or tag messages:

git tag -l -n1

18. April 2011

NVIDIA CUDA disable/enable ECC

Johannes Habich, 13:30 Uhr in CUDA

Show ECC config nvidia-smi -r
Enable ECC on GPU 0: nvidia-smi -g 0 -e 1
Disable ECC on GPU 0: nvidia-smi -g 0 -e 0

You need a reboot to get settings active

7. April 2011

EMACS: Whitespaces

Johannes Habich, 08:30 Uhr in Tools

Each and every editor handles whitespaces tabs etc. differently. The first step to get everyting out to the open is so show whitespaces and tabs the way the editor sees them. For me it’s emacs and the following lines in your ~/.emacs should give you a good view of whitespaces.
Look at this documentation for all references

Please be patient and drop me a comment if there are any errors or misunderstandings. I’m really no emacs pro!!!

(require 'whitespace)
(global-whitespace-mode t)

28. March 2011

GIT: Remote branches

Johannes Habich, 13:23 Uhr in Tools

Show remote branches:
git remote show origin

16. March 2011

GIT: Pushing a new repository to a git server the first time

Johannes Habich, 07:21 Uhr in Tools

You created some local repository and worked on that for a while. Now you want to have it on a server so that others can collaborate.
We want to keep the full history so we want to push the current repository to the server. In order to do this at least for the master branch you have to edit the config file at:
It probably looks like the following:
repositoryformatversion = 0
filemode = true
bare = false
logallrefupdates = true

The easiest way to get everything right is to check out the empty repository from the server via git clone and diff the two config files.
Finally you see that you have to add something like:
[remote "origin"]
fetch = +refs/heads/*:refs/remotes/origin/*
url =
[branch "master"]
remote = origin
merge = refs/heads/master

To the existing config.

Now issue a git push origin master and the master will be pushed.
If you know whether that works with branches as well or how to get that working, please drop me a comment!?

There are other ways to just give the repository as a argument at the git push command but I like to keep my old directories.

26. January 2011

GIT: Merging changes of a branch back to master

Johannes Habich, 12:28 Uhr in Tools

You branched out for development and now it is time to get the improvements back to the master branch.
This is achieve by git merge while on the master branch.

To be sure to not mess up anything, I prefer to clone my repository first and do the merge there.
So best is if you commit all changes in master and dev branch. Do a couple of pushs and pulls so everything is in sync and then clone your repository to a new location.
You can directly clone the branch you want to merge then proceed to 2. otherwise do a

  • git checkout branchname
  • git checkout master
  • git merge branchname

You have to resolve any conflicts in any files by removing the spiky brackets in the file and of course take a close look what caused the conflict and fix it.
Then add the file via git add and commit it via git commit .
Do this for every file.

20. January 2011

CVS: Get new directories of the server

Johannes Habich, 10:09 Uhr in Tools

If you want to update your CVS working copy to get new directories from the server, a simple cvs up does not get these directories.
Try cvs up -d

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