[ncl-talk] delete() is not clearing memory?

[Walter Hannah]

I'm having lots of "malloc" errors lately, and I realized that when I use
the "delete" function, NCL doesn't free up as much memory as it created!!!

After doing some sleuthing I figured out that the problem happens after I
use the reassingment operator ":=" to reduce a variable to a subset of
itself like this:

X := X(0,:)


I've come up with a stand alone NCL script (see below) that anyone should
be able to run on a linux machine to reproduce the problem. It prints out
the memory usage from the "ps" command.

procedure printMem (msg)
local rss,cmd
begin
    cmd = "ps --no-headers  -o 'rss' -C ncl"
    rss = max(toint(systemfunc(cmd))) / 1024.
    print("NCL memory:    "+sprintf("%6.2f",rss)+"     "+msg)
end

begin
    dims = (/10000,100,100/)

    print("")
    printMem("basline memory")
    print("")
    ;-----------------------------------------------------
    ;-----------------------------------------------------
    X = new( dims ,float)
    printMem("X created")
    delete(X)
    printMem("X deleted")
    print("")
    ;-----------------------------------------------------
    ;-----------------------------------------------------
    X = new( dims ,float)
    printMem("X created")
    X := X
    printMem("X reassigned")
    delete(X)
    printMem("X deleted")
    print("")
    ;-----------------------------------------------------
    ;-----------------------------------------------------
end


The output of the script on my linux machine is:

(0)
(0) NCL memory:     74.38     basline memory
(0)
(0) NCL memory:    456.11     X created
(0) NCL memory:     74.66     X deleted
(0)
(0) NCL memory:    456.13     X created
(0) NCL memory:    837.44     X reassigned
(0) NCL memory:    456.14     X deleted
(0)


So, after using doing the reassignment it seems that a copy of the variable
is left in memory and never cleared.

I can work around it for now, but I wanted to ask if anyone knew about
this, and also can it be fixed?

Thanks,
Walter Hannah
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