On Fri, 29 Dec 2023, Amir via fpc-pascal wrote:
On Dec 29, 2023 9:50 PM, Adriaan van Os <adri...@adriaan.biz> wrote:
Amir--- via fpc-pascal wrote:
> Hi all,
>
> I have a List of record, where the record has a WideString field.
> I have some code like the following:
>
> function check(constref v: TMyRecord; data: TListOfMyRecord): Boolean;
> var
> r: TMyRecord;
>
> begin
> Result := False;
> for r in data do
> if r.State = v.State then
> Exit(True);
> end;
>
> I call this method a lot and the CPU profiling shows a lot of cpu time
> spent on "fpc_copy_proc" (which I assume is doing the deep copy on
> records) from "TCustomListEnumerator.GetCurrent".
> I considered other alternatives like using enumerators but they all need
> a to return a record (and hence copying the widestring field).
> I can think of two solutions to get rid of the wasting(!) so much time
> on "fpc_copy_proc":
> 1) Changing the TMyRecord to TMyClass. But then I need to Create and
> Free a "lot" of objects.
> 2) Update TListOfMyRecord to TListOfPointerToMyRecord. This requires a
> "lot" of memory allocation/fragmentation.
>
> Is there a better solution?
Pass the data parameter by reference.
This means I need to have a ListOfMyRecord and a ListOfConstRefMyRecord, right?
It means you use
constref data: TListOfMyRecord
or
var data: TListOfMyRecord
And try to avoid "for r in data" because it will create a copy for each element
in the list.
I don't know how you defined TListOfMyRecord, but if it is a
generic TList<TMyRecord>, better change it to a TArray<TMyRecord> or Array
of TMyRecord, in which case you can use a pointer to the consecutive records
in the array. Generics are convenient, but slow.
Michael.
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