Same sscan record step size for all positioners not possible?

["J. Lewis Muir via Tech-talk" <tech-talk at aps.anl.gov>]

Hi, Tech-Talkers!

I've come across what I think is a bug in the sscan record of sscan
R2-11-6, where if I have two or more positioners configured for a
relative scan starting at 0 with the same start, center, end, step, and
width, I can change the step of one positioner, but the step of the
others gets changed to be not exactly the same as what I just set the
step of the one positioner to.  In my case, if I set the step of the
first positioner, the other steps get adjusted slightly, and the sscan
record ends up moving the first positioner one less scan step than the
rest.  I have AFTER SCAN set to STAY, so after running a scan where the
positioners are motors, I can see this because the total scan width
moved is reflected in the motor positions except for the first motor,
which is short by one sscan positioner step.

For example, attached is a screenshot showing this behavior.  I have
positioners 1-3 configured as follows:

  START: 0.0
  CENTER: -0.7
  END: -1.4
  STEP: -0.05
  WIDTH: -1.4
  ABS/REL: RELATIVE

But only one positioner can apparently have STEP set to -0.05.  In this
case, positioner 1 has STEP set to -0.05.  The STEP for positioner 2 and
3 is -0.052.  If I change STEP of positioner 2 to be -0.05, then STEP of
positioner 1 and 3 becomes -0.052.

Has anyone else seen this behavior?

(I see that sscan R2-12 was released a few months ago, but I don't see
anything in the release notes nor commit history that looks related to
this issue, so I didn't try upgrading.)

Environment:

* sscan R2-11-6
* EPICS 7.0.8.1
* EPICS Architecture: linux-x86_64
* OS: AlmaLinux 9.4

Thanks,

Lewis

Attachment: sscan-positioners-same-step-not-possible.png
Description: PNG image