Short answer: ensure you compile your program on the same CPU architecture as the compute node you will then run it on.

You may run across an error when you try to run an application that tells you the operating system or processor does not support certain instructions. This is often accompanied by a list of acronyms which correspond to the instructions. This is an example error message:

Please verify that both the operating system and the processor support Intel(R) X87, CMOV, MMX, FXSAVE, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, MOVBE, POPCNT, AVX, F16C, FMA, BMI, LZCNT, AVX2, AVX512F, AVX512DQ, ADX, AVX512CD, AVX512BW and AVX512VL instructions.

This happens because your program was compiled in a system that supports these instructions, but is running in a system that doesn't. Most likely you may have compiled your program on a different node than the one you are running your program from.

To get around this, you can make sure you compile your program in the same system that it will run. For example: if you need to run your program on one of the himem nodes, then you can submit a job that compiles your program, and subsequent jobs that then use the resulting executables to run your program. Alternatively, you can start an interactive session on a node with the target CPU architecture and compile your code interactively there. For example, assuming you want to compile your program for the himem nodes you could do srun –time=01:00:00 –partition=himem –pty /bin/bash. This will queue an interactive session lasting up to one hour on which you can compile your code.

In order to bring Hábrók back online after an incident we sometimes have to reinstall and reconfigure the login and interactive nodes. Because of this, these nodes will have new server host keys. This means that connecting to Hábrók results in (correct) warnings that these keys no longer match those that had been registered on your system when you connected for the first time.

Normally, checking the server hostkey ensures that you are not inadvertently connecting to a system posing as Hábrók (known as a man-in-the-middle attack) by warning you that you are actually connecting to another machine. You can safely ignore this check at this time because Hábrók's host keys have indeed changed due to the reinstallation.

When reconnecting you will see a pop up window. Simply press “Accept the new server hostkey and carry on connecting”

You will see a message with:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ED25519 key sent by the remote host is
SHA256:LnOMDB7/5L0OKJojsXb2CovSUGvd2k0U0oJ8L3xR2HI.
Please contact your system administrator.
Add correct host key in /home/user/.ssh/known_hosts to get rid of this message.
Offending ED25519 key in /home/user/.ssh/known_hosts:13
  remove with:
  ssh-keygen -f "/home/user/.ssh/known_hosts" -R "login1.hb.hpc.rug.nl"
Host key for login1.hb.hpc.rug.nl has changed and you have requested strict checking.
Host key verification failed.

Follow the instructions on the message and run:

ssh-keygen -f "/home/user/.ssh/known_hosts" -R "login1.hb.hpc.rug.nl"

Note that your command may be different, as the path to the known_hosts file is likely different in your situation. The suggestion in the warning message should give you the correct path.