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Fill an array with assembler

Posted on 2002-06-10
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I would like to fill an dynamic array of
arbitrary size with a value:

procedure FillWithValue(arr:pointer;n:longint;fval:double);assembler;
begin
asm
// ???
end;
end;

type tArr = array[0..0] of double;
pArr = ^tArr;

procedure Process;
var i:longint;
arr:pArr;
count:longint;
begin
count:=3000; // arbirary value
getmem(arr,count*sizeof(double));
for i:=0 to count-1
do begin
arr^[i]:=2*i;  // arbitrary start value
end;
i:=200;
ShowMessage(floattostr(arr^[i]));
// now fill with the whole array with 0.0
FillWithValue(arr,count,0.0);
freemem(arr);
end;

Can someone help me with the assembler code
to put fval into all elements of arr?

Thanks for help,

Gamba

0
Question by:Gamba

LVL 12

Expert Comment

why don't you simply use FillChar
I'm sure it's highly optimized :)

you could also write some code with FillChar and check the asm procedure it creates :)
0

LVL 14

Expert Comment

I think it's becoz he's trying to fill the array with double and not char :)
0

LVL 12

Expert Comment

umm yes ...
well filling the array with all 0.0 is the same as filling it with 0 chars :)
0

LVL 14

Expert Comment

Umm... true... I didn't see that part of filling with 0.0... lol

So Gamba, just use

FillChar(YourArray, 0, SizeOf(YourArray));
0

LVL 14

Expert Comment

PS: If it works, please give the points to Lee and not to me :)
0

LVL 12

Expert Comment

hehe tnx :)

anyway it should be like :
FillChar(YourArray, Length(YourArray) * SizeOf(Double), 0)
0

LVL 14

Expert Comment

Oops... here I go again... must be getting old ;)
0

LVL 9

Expert Comment

hi gamba,
why do you need assembler code? It is difficult to write assembler code for short operations that works faster then Delphi build. Delphi does excellent optimization and in some cases writing fastest code inside one procedure in assembler will slow down whole process. It is due to Delphi can't optimize procedure that calls procedure writen in assembler.

Just use this way to work with array of doubles:

var
A: Array of Double;
I: Integer;
begin

SetLength(A, 12);
for I := Low(A) to High(A) do
A[I] := I * 2;
end;

-------
Igor.
0

Author Comment

You're right in that FillChar would be an alternative
for filling with zeros. But this was meant only as an
example for accessing the array via assembler.
What I want to do in the end is processing a huge
array of floating point values with assembler, thereby
accessing the FPU direct to do mathematical operations
on the array.
So I need the assembler code for getting started at all.

Gamba

0

LVL 1

Expert Comment

No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

PAQ and No Refund

Paul (pnh73)
EE Cleanup Volunteer
0

LVL 6

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