How to monitor and reduce CPU usage in WD 3.2.3, if necessary

WD 3.2.x finds a few more spot and more information about WSPT-2 spots by decoding each 2 minute wav file recording two times.

In the first pass WD runs the standard wsprd decoder which can find beacon signals which are drifting up to 4 Hz. In the second pass WD runs an enhanced version of wsprd which reports the doppler shift/frequency spreading of the signal but doesn't attempt to compensate for transmitter drift. In my testing at KPH, about 97% of the spots are reported by both passes. About 2% are reported only by the first (drift-compensating) pass and about 1% of the total spots are reported only by the second (spreading/doppler shift) pass. So at a high performance QTH by de-tuning the first pass so it uses little CPU you may see 1% fewer spots, but even then you probably get the same number of spots as you would get with only the first pass running at full search setting.

Since running the wsprd decoder is a CPU bound operation, doubling the number of runs of wsprd will double the time when your CPU is 100% busy. To determine if there is enough CPU power for this 'two-pass' decoding I observer the CPU strip chart display of the 'btop program. If you observe the 'sawtooth' pattern shown here, then you probably have enough CPU power

If there are few or no gaps in the strip chart, you can change WD 3.2.3 to very efficiently perform the first pass of wsprd by adding this line to your config file. This should reduce CPU usage by almost 50%.

WSPRD_FAST_FIRST_PASS="yes"