[Linrad] Re: Linrad-02.54

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Mart and All,

> There seems to be a problem with the "total amplitude calibration"
> function in ver 2.53 and 2.54 . When you get to the last page in the
> pulse calibration sequence and all data has been calculated, at the
> Y=>Accept prompt the program hangs (win version).
And the same under Linux.....

This bug is a typical example on why it is important to me
to get bug reports as fast as possible. It is much easier
to find the reason why something that used to work no
longer does so if the time since I made a mistake is short.

I surely understand that those of you who have an old version
that works well are reluctant to take the trouble to install
a new version and possibly find that the new version creates
problems. Your trouble - if it happens - is my help!

The calibration error is caused by a change I made in order 
to make Linrad more tolerant to unfriendly programs that 
use the CPU heavily now and then. (For X11 and Windows users.)

The Linrad user may ask for a low DMA rate to allocate 
large buffers for the input and output. A user who 
also sets a large output delay margin can have a lot 
of data waiting in the various buffers within Linrad
and with 2.53 the different threads (hopefully) wait for
free space in the subsequent processing step to avoid
overwriting data and thus the output of linrad can
stay correct even under difficult CPU load conditions.
(But with a somewhat longer processing delay)

As a side effect the calibration thread hangs when one
presses Y because the fft1 thread finds that the buffer
of the calibration routine is full. I forgot to do
the appropriate modification to mark the buffer as
empty after the (long) time it takes the user to
press Y.

The calibration thread waits on a semaphore for a new 
fft1 transform but the fft1 thread waits (sleeping) for 
the calibration thread to mark old data as used.....

This is a typical example when a small change at one place
causes an unexpected error at some other place.
(Of course it should not have been unexpected.....)

Again: Rapid feedback on errors is most helpful:-)

The bug is corrected in Linrad-02.55

73

Leif / SM5BSZ

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