ItsMods

- Math in Assembly By Ohad Klein And NieXrlaM (David)

how to do Square root in assembly?

the follow code will do this function

Code:
push Num

call sqrt

pop Num

sqrt:

pop eax

fld DWORD PTR [eax]

fsqrt

fstp DWORD ptr[eax]

push eax

retn

at c++ the code will be like this

Code:
inline float Sqrt(float Num)

{

    _asm

    {

        fld DWORD PTR [Num]

        fsqrt

        fstp DWORD ptr[Num]

    }

    return Num;

}

how to do Sine in assembly?

the follow code will do this function

Code:
push Rad

call Sine

pop Rad

Sine:

pop eax

fld DWORD PTR [eax]

fsin

fstp DWORD PTR [eax] 

push eax

retn

at c++ the code will be like this

Code:
inline float Sine(float Rad)

{

    _asm

    {

        fld DWORD PTR [Rad]

        fsin

        fstp DWORD PTR [Rad] 

    }

    return Rad;

}

same at cosine
just change from "fsin" to "fcos"

how to do tangents in assembly?

the follow code will do this function

Code:
push Rad

call tan

pop Rad

tan:

pop eax

fld DWORD PTR [eax]

fsincos

fdiv

fstp DWORD PTR [eax]

push eax

retn

How i can Prove it ?
answer..
sine(alpha)/cosine(alpha) = tangents(alpha)

at c++ the code will be like this

Code:
inline float Tan(float Rad)

{

    _asm

    {

        fld DWORD PTR [Rad]

        fsincos

        fdiv

        fstp DWORD PTR [Rad]

    }

    return Rad;

}

how to do Arc tangents in assembly?

the follow code will do this function

Code:
push Rad

call Atan

pop Rad

Atan:

pop eax

fld dword ptr [eax]

fld1

fpatan

fstp dword ptr [eax]

push eax

retn

at c++ the code will be like this

Code:
inline float Atan(float Rad)

{

    _asm{

    fld dword ptr [Rad]

    fld1

    fpatan

    fstp dword ptr [Rad]

    }

    return Rad;

}

also .. if you want to do
Asin or Acos functions ..
you will use this logic (C++)

Code:
inline float Asin(float Rad)

{

    Rad = Sqrt(Rad*Rad/(1-Rad*Rad));

    Rad = Atan(Rad);

    return Rad;

}

inline float Acos(float Rad)

{

    Rad = Sqrt((1-Rad*Rad)/(Rad*Rad));

    Rad = Atan(Rad);

    return Rad;

}

How i can Prove it ?
answer..

Asin(x) = Atan(((x*x/(1-x*x))^0.5)
Acos(x) = Atan(((1-x*x)/(x*x))^0.5)

how to do Exponentiation in assembly?

the follow code will do this function

Code:
push Base

push Power

call Pow

pop Num

Pow:

pop edx

pop ebx

fld DWORD PTR [edx]

fld DWORD PTR [ebx]

fld1

fsub

fyl2xp1

sub     esp,16                                ; z = x*log2 

fist    DWORD PTR [esp+12]            ; round 

fld1

fstp    TBYTE PTR [esp]

fisub   DWORD PTR [esp+12]            ; z - round 

mov     eax, [esp+12]

add     [esp+8],eax

f2xm1

fld1

fadd

fld     TBYTE PTR [esp]               ; 2^(round )

fmul                                  ; 2^z = e^x

add     esp,16

fstp DWORD PTR [ebx]

push ebx

retn

at c++ the code will be like this

Code:
inline float Pow(float Base, float Power)

{

    _asm

    {

        fld DWORD PTR [Power]

        fld DWORD PTR [Base]

        fld1

        fsub

        fyl2xp1

        sub     esp,16                                ; z = x*log2 

        fist    DWORD PTR [esp+12]            ; round 

        fld1

        fstp    TBYTE PTR [esp]

        fisub   DWORD PTR [esp+12]            ; z - round 

        mov     eax, [esp+12]

        add     [esp+8],eax

        f2xm1

        fld1

        fadd

        fld     TBYTE PTR [esp]               ; 2^(round )

        fmul                                  ; 2^z = e^x

        add     esp,16

        fstp DWORD PTR [Base]

    }

    return Base;

}

For more functions download the attachment file

Enjoy Smile

(and sorry for my english)

Interesting, how about mod (remainder)?

Great stuff, but I had a problem with your SinCos function.

Code:
inline void SinCos(float Rad, float &sinAns, float &cosAns)

{

    _asm

    {

        fld DWORD PTR [Rad]

        fsincos

        fstp    dword ptr [sinAns]

        fstp    dword ptr [cosAns]

    }

}

The first problem is the result from the function was always 0 for both sin and cos. I had to put the sinAns and cosAns into some registers for it to work.

Code:
inline void SinCos(float Rad, float &sinAns, float &cosAns)

{

    _asm

    {

        FLD        DWORD PTR [Rad]

        FSINCOS

        MOV        EAX, DWORD PTR [cosAns]

        MOV        ECX, DWORD PTR [sinAns]

        FSTP    DWORD PTR [EAX]

        FSTP    DWORD PTR [ECX]

    }

}

Second, I had to flip the cos and sine popping around so it gets cos first then sine. I am not sure why this is, because the documentation I read says Cos is in S0 and Sine is in S1. Very odd....

(10-08-2011, 07:58)skidz Wrote: [ -> ]Great stuff, but I had a problem with your SinCos function.

Code:
inline void SinCos(float Rad, float &sinAns, float &cosAns) { _asm { fld DWORD PTR [Rad] fsincos fstp dword ptr [sinAns] fstp dword ptr [cosAns] } }

The first problem is the result from the function was always 0 for both sin and cos. I had to put the sinAns and cosAns into some registers for it to work.

Code:
inline void SinCos(float Rad, float &sinAns, float &cosAns) { _asm { fld DWORD PTR [Rad] fsincos mov eax, DWORD PTR[cosAns] mov edx, DWORD PTR[sinAns] fstp DWORD PTR[eax] fstp DWORD PTR[edx] } }

Second, I had to flip the cos and sine popping around so it gets cos first then sine. I am not sure why this is, because the documentation I read says Cos is in S0 and Sine is in S1. Very odd....

yea.. this code is very old.. and not coded right,
thnx for the Note Smile

NieXrlaM

deadIce

skidz

NieXrlaM