) Delphi fast algorithm for finding the minimum value of an out-of-order array (application 3 of Delphi MMX Optimization Algorithm)

Type

Pmylist = ^ tmylist;

Tmylist = array of word;

Function getminvalue (list: pmylist): word; stdcall;

VaR

Forcount, listcount, I: DWORD;

Maxvaule: int64;

List0address: DWORD;

Begin

Result: = $ 7fff;

Listcount: = high (list ^) + 1;

If (listcount <16) or (listcount mod 16) <> 0) then

Begin

For I: = 0 to listcount-1 do

Begin

If list ^ [I] <result then result: = List ^ [I];

End;

End else

Begin

Maxvaule: = $ 7fff7fff7fff7fff;

List0address: = DWORD (@ list ^ [0]);

Forcount: = listcount Div 16; // 4 * MMX

ASM

Push eax

Push ECx

Push ESI

MoV ESI, list0address // start address

MoV ECx, forcount // Length

Movq mm0, maxvaule

MoV eax, 0

@ Cmploop:

Prefetchnta [ESI + eax + 1024] // fetch ahead by 1024 bytes

Movq MM1, qword [ESI + eax]

Movq mm2, qword [ESI + eax + 8]

Movq mm3, qword [ESI + eax + 16]

Movq mm4, qword [ESI + eax + 24]

Pminsw mm0, MM1

Pminsw mm0, mm2

Pminsw mm0, mm3

Pminsw mm0, mm4

Add eax, 32

Sub ECx, 1

Jnz @ cmploop

Movq MM1, mm0

Psrscsi MM1, $20 // shift right

Pminsw mm0, MM1

Movq MM1, mm0

Psrscsi MM1, $10 // shift right

Pminsw mm0, MM1

Movd eax, mm0

MoV result, ax

Sfence

Emms

Pop ESI

Pop ECx

Pop eax

End;

End;

End;