Using Wilfried's asm code and Rob's tight Delphi code as inspiration and jumping off point: This is my first ASM routine ever.
function Max3(a, b, c: integer): integer; // eax : first param & Result // ecx : second param // edx : third param asm cmp eax, ecx jl @less // ecx > eax cmp eax, edx jl @less2 // eax > ecx but less than edx. edx is max. 2 compares, 1, assignment, 1 jump ret // eax is max. 2 compares, 0 assignments, 0 jumps @less: // ecx > eax.. Is ecx greater than edx? cmp ecx, edx jl @less2 // edx is max. 2 compares, 1 assignment, 2 jumps mov eax, ecx // ecx is max. 2 compares, 1 assignment, 1 jump ret @less2: mov eax, edx // edx is max end; Warmest regards and thanks for the inspiration, -- Jon Grewer > Message: 1 > Date: Sat, 25 Aug 2007 23:06:56 +0200 > From: CubicDesign <[EMAIL PROTECTED]> > Subject: Re: maximum of 3 numbers > To: Borland's Delphi Discussion List <[email protected]> > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > > > Rob Kennedy wrote: > >> The name of that unit suggests it's a unit written for the Intel 80387 >> math coprocessor; is it really that old? >> >> > I don't know. There was no source code, only a DCU. But it is for Delphi. > I have found also a library (with the same name) which is for Pascal :) > >> Being written in assembler and performing the same as the function in the >> Math unit aren't mutually exclusive things. >> >> > The DCU was offered as a faster replacement for Borland functions. It > didn't performed much better. > Indeed this doesn't mean that the code was not written in ASM. Anyway I > never said that it wasn't made in ASM. I just said that the speed of > that DCU was similar with Borland's. > Usually ones expect at least a 2x speed improvement from an ASM code > (also a 5x speed improvement is not exaggerated). > >> For one hundred million things, that seems pretty fast already. How fast >> do you want it go instead? >> >> > The speed of my code (2 sec) is ok but there are also other pieces of > code in that loop, so the total time for the whole the loop can go up to > 10-30 seconds. > Anyway I got a piece of code in ASM from Wilfried (thanks again > Wilfried) which is about 2-3 times faster than my plain Delphi code. > Yesterday I spend the whole day optimizing that loop and I decreased the > time with about 50-55%. > Is still unacceptable since I have lot of data to process. > > I have only minor understanding of ASM (enough to understand ASM code > but not enough to write) so I am thinking seriously in learning more ASM. > > > >> That executes two comparisons and a maximum of three assignments. >> >> function Max(const A, B, C: Integer): Integer; >> begin >> if A > B then >> if A > C then >> Result := A >> else >> Result := C >> else >> if B > C then >> Result := B >> else >> Result := C; >> end; >> >> That executes two comparisons and a maximum of one assignment. >> >> >> > Great! Sure it will execute faster than mine. Indeed it will execute > comparisons to get the final result. > Thank you very much. > > It is funny how a piece of code can get faster by using more lines of > code :) > > _______________________________________________ Delphi mailing list -> [email protected] http://www.elists.org/mailman/listinfo/delphi
