From Newsgroup: comp.lang.tcl

Sorry this may be quite basic but just wanted to confirm it:

Let's say that I have a proc which generates a large dict and returns
it. Then when used, the caller assigns it to a variable.

How much memory is used, 10mb or 20mb? (let's ignore any extra memory
needed to manage the dict structure and the proc calls).


proc generate_10mb_dict {a b c} {
# generate a large dict, in d

return $d
}

set my_data [generate_10mb_dict $a $b $c]


what is the ram use at this point?

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From Newsgroup: comp.lang.tcl

saito <saitology9@gmail.com> wrote:

Sorry this may be quite basic but just wanted to confirm it:

Let's say that I have a proc which generates a large dict and returns
it. Then when used, the caller assigns it to a variable.

How much memory is used, 10mb or 20mb? (let's ignore any extra memory
needed to manage the dict structure and the proc calls).

proc generate_10mb_dict {a b c} {
# generate a large dict, in d

return $d
}

set my_data [generate_10mb_dict $a $b $c]

what is the ram use at this point?

Given your sample code, the usage is the amount taken up by the dict.

If the dict is 10mb (as you suggest) then after "set my_data" the ram
usage is 10mb.
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From Newsgroup: comp.lang.tcl

On 8/8/2024 4:27 PM, Rich wrote:

Given your sample code, the usage is the amount taken up by the dict.

If the dict is 10mb (as you suggest) then after "set my_data" the ram
usage is 10mb.

Thank you!
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From Newsgroup: comp.lang.tcl

Am 09.08.2024 um 01:39 schrieb saito:

On 8/8/2024 4:27 PM, Rich wrote:

Given your sample code, the usage is the amount taken up by the dict.

If the dict is 10mb (as you suggest) then after "set my_data" the ram
usage is 10mb.

Thank you!

Yes, TCL uses generally shared values with referent count.
And each item is reference counted. And with TCL 9, even sublists are reference counted, e.g. stored only once.

That means:

set d [dict create a [string repeat a 100000]]

d and a are reference counted.

dict set d b [dict get $d a]

does not copy the string, but reference it twice.

A copy of the data is only done, if the data gets different:

dict set d b "[dict get $d b]q"

Now, dict item a and b are differently and thus b is copied.

Anyway, it is endlessly complicated...

Harald
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From Newsgroup: comp.lang.tcl

On 8/9/2024 2:22 AM, Harald Oehlmann wrote:

Now, dict item a and b are differently and thus b is copied.

Anyway, it is endlessly complicated...

:-)

Thanks for the details. That makes sense.

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