Hi all,
Thanks for a busy ~20 hours of many people testing FT8. I now have
accumulated a directory with 527 *.wav files, each of which has at least
one visible FT8 signal. The files were recorded at K1JT at either
14.079 or 50.313 MHz.
Running the r7753 stand-alone slow-mode decoder jt9[.exe] on this
collection of files produces 574 valid decodes and 0 false decodes with
total execution time 39.8 s. The average time to process a 15 s Rx
sequence on this machine (Core i7-6700 @ 3.4 GHz) is thus 39.8/527 =
0.076 s. Not bad!
Here's the detailed execution-time breakdown from timer.out:
Name Time Frac dTime dFrac Calls
----------------------------------------------------------
jt9 39.828 1.00 0.734 0.02 1
read_wav 0.121 0.00 0.121 0.00 27404
decft8 38.973 0.98 0.133 0.00 527
sync8 4.191 0.11 4.191 0.11 527
ft8b 34.648 0.87 0.051 0.00 2821
bpd174 1.480 0.04 1.480 0.04 2821
osd174 33.117 0.83 33.117 0.83 2210
----------------------------------------------------------
39.828 1.00
Note that 83% of the execution time is spent in routine osd174, 11% in
sync8, and 4% in bpd174 (a contraction for subroutine name bpdecode174).
It turns out that only 14 of the 574 decodes were produced by osd174,
the "ordered statistics" decoder. The rest came from bpd174. With
osd174 deactivated, timer.out looks like this:
Name Time Frac dTime dFrac Calls
----------------------------------------------------------
jt9 6.641 1.00 0.891 0.13 1
read_wav 0.168 0.03 0.168 0.03 27404
decft8 5.582 0.84 0.094 0.01 527
sync8 3.887 0.59 3.887 0.59 527
ft8b 1.602 0.24 0.109 0.02 2821
bpd174 1.492 0.22 1.492 0.22 2821
osd174 0.000 0.00 0.000 0.00 2210
----------------------------------------------------------
6.641 1.00
Now the average execution time for a 15 s Rx sequence is just 13 ms!
We need to keep decoding time very short -- say, well under 1 s -- so
that auto-sequencing, if not the human operator, can select proper
responses to received messages. Fortunately, we already have good
baseline performance -- and we have a number of "knobs" to play with.
-- Joe, K1JT
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