Problems installing wsclean

[JSKenyon]

On Ubuntu 20.04 using KERN-7, wsclean fails to install with messages like:

sudo apt install wsclean
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 wsclean : Depends: libwsclean2 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

I have verified that I have no held packages and I believe that I ran into the same issue on my previous PopOS install.

[Athanaseus]

Thanks for the issue @JSKenyon.

Can you please provide output of apt search wsclean

[JSKenyon]

apt search wsclean
Sorting... Done
Full Text Search... Done
libwsclean2/focal 2.10.1-1kern1 amd64
  Fast generic widefield interferometric imager (shared library)

wsclean/focal 2.10.1-1kern1 amd64
  Fast generic widefield interferometric imager

wsclean-dev/focal 2.10.1-1kern1 amd64
  Fast generic widefield interferometric imager (development files)

[Athanaseus]

Somehow I cannot reproduce this error.
It installs successfully on my ubuntu20 desktop and on a docker container.

Also make sure that the restricted and multiverse:
sudo apt-add-repository multiverse
sudo apt-add-repository restricted

[JSKenyon]

I already have both of those - maybe something strange has happened. I find it odd that I ran into this on my old system too. Completely possible that the error is on my end. I already went ahead an installed from source so this isn't blocking me. Just strange that this and only this seems to give me problems.

[gijzelaerr]

What error do you get if you apt-get install libwsclean2

[JSKenyon]

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libwsclean2 : Depends: libidg-api0 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

[gijzelaerr]

And what happens if you install libidg0-api0 manually? Follow the trail

[JSKenyon]

Ah, it is the image domain gridding stuff. It wants cuda related dependencies. Perhaps because I have a GPU?

sudo apt install libidg-api0 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libidg-api0 : Depends: libidg-cuda0 but it is not going to be installed
               Depends: libidg-hybrid-cuda0 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

sudo apt install libidg-cuda0
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libidg-cuda0 : Depends: libnvidia-compute-418-server but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

[JSKenyon]

I can follow along further - just shout if you think it is needed.

[gijzelaerr]

yeah please follow. it looks like it can't install nvidia drivers and cuda. is your system up-to-date using apt-get upgrade? Are you sure you have restricted enabled? can you install cuda?

[JSKenyon]

Looks like that last one was the problem. I manually installed libnvidia-compute-418-server and now I can install wsclean. I do not know why that specific package would cause a problem though.

[Athanaseus]

is your system up-to-date using apt-get upgrade?

This rings a bell. The last time I've experienced this it was solved by updating the system and clearing cache.

sudo apt update
sudo apt upgrade && sudo apt clean

https://itsfoss.com/clear-apt-cache/

[JSKenyon]

I cannot really say. I do know that installation failed literally just after I did a fresh Ubuntu install, so I wouldn't have thought there could be any state to cause problems.

[o-smirnov]

I can confirm this is still a problem @gijzelaerr @Athanaseus.

$ sudo apt install wsclean libwsclean2 libidg-api0 libidg-cuda0
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libidg-api0 : Depends: libidg-hybrid-cuda0 but it is not going to be installed
 libidg-cuda0 : Depends: libnvidia-compute-418-server but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
oms@ike:~$

Why is there a hard dependency on libnvidia-compute-418-server? In any case, I can't install that version since it doesn't support the GPUs in that particular mode. Perhaps the package should be repackaged with an optional dependency? 99% of our use cases of wsclean don't even involve CUDA, so it should not be holding us back?

[Athanaseus]

Why is there a hard dependency on libnvidia-compute-418-server? ...

This is due to the hard dependency on idg-dev which requires Cuda libraries.
I will repackage the wsclean package with an optional dependency.
Perhaps in the upcoming kern release, we can have wsclean and wsclean-idg.