[gradsusr] 'flush' command does not work

[Brandon Schmidt]

Through extensive debugging, I've found that the GrADS *flush* function
does not work properly. This first came to my realization when I began to
automate my GrADS scripts. Each script processes a single hour by
downloading a GRIB file, creating a control file, opening the control file,
and displaying/outputting the needed data. The scripts initialize with
right around 100 MB of memory but through execution, they can rack up as
much as 1.4 GB. Of course when processing multiple hours, this slowed my
server to a crawl and in some cases caused crashes (especially with
high-res HRRR data for example). Anyway, I traced the excessive memory
usage to the display commands. I am aware that with each display command,
the displayed variable is stored to the GrADS GRIB2 cache to eliminate
further decompression overhead. This is all well given the *flush* command
but it seems to only work half of the time. One can easily see this by
noting the initial memory, displaying a few variables, flushing, and then
noting the final memory. Seemingly randomly, the memory following a flush
will slowly creep up. The behavior memory-wise that I expected from *flush* can
only be obtained with *reinit* but calling that function thousands of times
is not an option. Any ideas as to a work-around or fix? I am using the
latest 2.1.a3 version. The first *flush* below works but the second does
not.

-Brandon

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ga-> !pgrep grads

7879

ga-> ! ps -p 7879 -o %mem,size

%MEM    SZ

 1.3 87276

ga-> d tmp2m

Notice:  Automatic Grid Interpolation Taking Place

Contouring: 255 to 305 interval 5

ga-> ! ps -p 7879 -o %mem,size

%MEM    SZ

 1.7 108024

ga-> d capesfc

Notice:  Automatic Grid Interpolation Taking Place

Contouring: 0 to 3500 interval 500

ga-> set lat 50 70

LAT set to 50 70

ga-> d gustsfc

Notice:  Automatic Grid Interpolation Taking Place

Contouring: 1 to 13 interval 1

ga-> set lat 20 90

LAT set to 20 90

ga-> d tmp2m

Notice:  Automatic Grid Interpolation Taking Place

Contouring: 255 to 305 interval 5

ga-> flush

grib2 cache cleared

ga-> ! ps -p 7879 -o %mem,size

%MEM    SZ

 1.7 108024

ga-> d tmp2m

Notice:  Automatic Grid Interpolation Taking Place

Contouring: 255 to 305 interval 5

ga-> ! ps -p 7879 -o %mem,size

%MEM    SZ

 1.9 122908

ga-> flush

grib2 cache cleared

ga-> ! ps -p 7879 -o %mem,size

%MEM    SZ

 1.9 122908

ga->
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