Fastest way to copy a record or an array of record
lazarus / 8-Other

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Zomis · 2007-02-08 16:16

I was wondering which the fastest way is to copy a record or an array
of record?
Is it onevar:=secondvar that is the fastest, or is it faster to use
some kind of CopyMemory function if it's avalible?

I need to copy one record of 33819 bytes
And one static array of 5672823 bytes (871 * 6513 bytes)
This copying will be done many many times, since it's for indexing
game levels into a database. For each new item, the old data must be
reset to default values.

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Manlio · 2021-05-30 09:18

I don't know why no one ever replied here, but I think it's an
interesting subject in many situations, and therefore I'll try to
answer it.

And my answer to the question is: MEASURE it.

Code: [Select]
// measure method #1
T := GetTickCount64;
for i := 1 to 1000000 do
  record1 := record2;
T1 := GetTickCount64 - T;

// measure method #2
T := GetTickCount64;
for i := 1 to 1000000 do
  Move(record1, record2, SizeOf(TRecord));
T2 := GetTickCount64 - T;

// and so on... run different methods and compare the time it takes

I have done similar things in the past and I often found surprising
results, e.g. sometimes assigning 0 to each field manually was faster
than using FillChar, things like that.

Bottom line, don't rely on guesses or reasoning when you can easily
measure.

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MarkMLl · 2021-05-30 09:26

Quote from: Manlio on May 30, 2021, 11:18:26 amI don't know why no one
ever replied here, but I think it's an interesting subject in many
situations, and therefore I'll try to answer it.

Because the question is 13 years old, the poster left the forum not
long after posting it, and the convention is that old threads are not
resurrected without /very/ good reason.

MarkMLl