Saturday, August 23, 2014

Csound and x86_64 machines

I could not understand why Sugar TamTam activities wouldn't play any sound on x86_64 even though the problem seemed resolved! It took a while to realize that the problem was with x86_64 architecture. I could get the sound to play on an i686 virtual machine.

Thanks to realtime Csound programming using Python, I could trace the fault. The issue is illustrated by the following code in

        if csnd.csoundGetSizeOfMYFLT() == 8:
            pfields = csnd.doubleArray(n)
            pfields = csnd.floatArray(n)
The csound client code in Python and C used by tamtam activities assumes a float array.

The following line in csound.spec from rpm source makes the issue pretty clear:

# Csound is really dumb about 64-bit
Rebuilding csound on x86_64 with "%define useDouble 0" even for x86_64 resolved the problem with TamTam activities.

However, it is entirely possible that this workaround may cause some other applications which use csound to fail on x86_64.

Wednesday, August 13, 2014

OpenStack - Virtual Machine stuck in task state 'powering-on'

Today for the second time I had to search for the solution in Last time, I seemed to have selected the right keywords but it took much more effort today.

I just needed to reset task_state in instances table of the nova database:
mysql -e "update instances set task_state = NULL \
           where deleted = 0 and hostname = 'master'" nova
The problem may be caused by error in nova compute starting up as I use virtual machine manager as well.

Virtual machine manager creates images in /var/lib/libvirt/images which are readable by root only.

For some reason, nova-compute looks in this directory as well and gets errors like:
Stderr: "qemu-img: Could not open '/var/lib/libvirt/images/fedora20.qcow2': Permission denied\n"
I manually change the permissions to readable by all to overcome the problem.