Experimental Physics and
Industrial Control System

On Fri, Jul 17, 2015 at 4:42 PM, Matthew D. Moore <[email protected]> wrote:

I am looking for a quick survey of people with a xspress3 from Quantum Detectors.

Do you you have any feedback on the driver?

Have you made any changes to the EPICS driver that aren't GiHub? If so, are you willing to put it up on GitHub?

> We are doing some work at Diamond - starting by simplifying the driver so that it has far
 > fewer parameters in the NDArray, and making it simpler to scale the system by number of
> channels. This should make it more performant and able to scale to higher speeds and/or > more channels.

I don't see these changes.  Is this code available?

> I would be interested if anyone actually uses the ROI's that are stored in the data file.

You mean the HDF5 data files?  Then, no.  The ROIs are not necessary here.  If one has the full array and knows the ROI definitions, these are as easy to extract as they are to read from a separate dataset. 

One thing we've found to be very important for performance is to use compression on the HDF5 files.   We typically acquire data for 10 to 100 ms per spectra.  Since the max count rate is ~3MHz and there are 4096 bins, the typical count is around 10 to 100 in each bin.   Even with the data stored as Int32 or Float32 (and especially as Float64), the data are highly compressible, and disk i/o dwarfs compression / decompression time.   We typically use Zlib compression level 1.

> These add a lot of attributes and have a lot of overhead - both manipulating the
> NDArray every frame, and also when writing the file at the end - because it writes
> all the parameters after the scan finishes.