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Fill an array with assembler

Posted on 2002-06-10
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Last Modified: 2010-04-04
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

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Question by:Gamba
11 Comments
 
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by:Lee_Nover
Comment Utility
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 :)
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by:DragonSlayer
Comment Utility
I think it's becoz he's trying to fill the array with double and not char :)
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Expert Comment

by:Lee_Nover
Comment Utility
umm yes ...
well filling the array with all 0.0 is the same as filling it with 0 chars :)
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by:DragonSlayer
Comment Utility
Umm... true... I didn't see that part of filling with 0.0... lol

So Gamba, just use

FillChar(YourArray, 0, SizeOf(YourArray));
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by:DragonSlayer
Comment Utility
PS: If it works, please give the points to Lee and not to me :)
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by:Lee_Nover
Comment Utility
hehe tnx :)

anyway it should be like :
FillChar(YourArray, Length(YourArray) * SizeOf(Double), 0)
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by:DragonSlayer
Comment Utility
Oops... here I go again... must be getting old ;)
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Expert Comment

by:ITugay
Comment Utility

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

by:Gamba
Comment Utility
Thanks for all comments!

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

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by:pnh73
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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

Please leave any comments here within the next seven days.
 
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!
 
Paul (pnh73)
EE Cleanup Volunteer
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