Random functions as core language functions

[kryton9]

Charles, I was wondering why you don't have random functions as part of the language core or have a math.inc that comes with oxygen?

In case you ever decide to add them, here is a nice site explaining all the popular functions and shows the algorithms.
http://www.johndcook.com/cpp_TR1_random.html

Additionally here is a list of what users coming from the c world might expect for math as part of the language and constants.
http://www.cs.cf.ac.uk/Dave/C/node17.html

[Charles Pegge]

Creating a Maths.inc: Good idea Kent.

At present there is no standard rnd() function. Some are good for speed, others for high statistical quality. Yet others for creating hash tables optimised for ascii.

Here are the speedy ones used in inc/glo2/texture.inc. The noise functions are slightly different in that an index number is passed to get a pseudo-random number. Each index value always returns the same number. This is a requirement of Perlin noise.

Code: OxygenBasic

1.   '===============
2.  'NOISE FUNCTIONS
3.  '===============
4.  
5.   Long seed=0x12345678 'initial seed value
6.  
7.   '-----------------------
8.  Function Rnd() as Single
9.   '=======================
10.  '
11.  Static As Single f, d=1/0x7fffffff
12.   mov eax,seed
13.   rol eax,7
14.   imul eax,eax,13
15.   mov seed,eax
16.   push eax
17.   fild dWord [esp]
18.   add esp,4
19.   fmul dWord d
20.   fstp dWord f
21.   Function=f
22.   End Function
23.  
24.   '---------------------
25.  Function Rndi() as sys
26.   '=====================
27.  '
28.  mov eax,seed
29.   xor eax,0x35353535
30.   imul eax,eax
31.   ror eax,17
32.   imul eax,seed
33.   ror eax,7
34.   mov seed,eax
35.   return eax
36.   End Function
37.  
38.  
39.   '------------------------------
40.  Function Noise(sys i) as Single
41.   '==============================
42.  Static As Single f, d=1/0x7fffffff
43.   mov eax,i
44.   xor eax,0x35353535
45.   imul eax,eax
46.   ror eax,17
47.   imul eax,i
48.   ror eax,7
49.   push eax
50.   fild dWord [esp]
51.   add esp,4
52.   fmul dWord d
53.   fstp dWord _return
54.   End Function
55.  
56.  
57.   '----------------------------
58.  Function Noiseb(sys i) as sys
59.   '============================
60.  Static As Single f, d=1/0x7fffffff
61.   mov eax,i
62.   xor eax,0x35353535
63.   imul eax,eax
64.   ror eax,17
65.   imul eax,i
66.   ror eax,7
67.   and eax,255
68.   mov _return,eax
69.   End Function
70.  
71.  

Charles

[kryton9]

Would the asm code run faster than code written in oxygen? If so, then I think it would be nice if you could assemble a math.inc library when you have some time.

[Charles Pegge]

There are 2 instructions unavailable in Basic: rol and ror. (rotating the bits to the left and to the right). Otherwise it would be possible to produce very similar binary without using any assembler.

Yes a maths source library could also include other useful algorithms like successive approximation, vector and matrix arithmetic and other tricky things that tax the mind.

We have examples for some of these already in the examples/math folder.

Charles

[JRS]

Otherwise it would be possible to produce very similar binary without using any assembler.

Sort of like building a log cabin with a hatchet. 

[Peter]

 

Sort of like building a log cabin with a hatchet.

 What then finally collapses. 

[Peter]

Hi Kent,

I do something of the kind:

Code: [Select]

double randDouble(double low, double high)
 {
 double temp;

 /* swap low & high around if the user makes no sense */
 if (low > high)
 {
 temp = low;
 low = high;
 high = temp;
 }

 /* calculate the random number & return it */
 temp = (rand() / (static_cast<double>(RAND_MAX) + 1.0))
 * (high - low) + low;
 return temp;
 }

[Charles Pegge]

If speed is a concern then I would avoid using an algorithm that involves division.

Division takes at least 30 clock cycles in contrast to multiplication (~2 cycles) and other arith/logic instructions.

Charles

[Peter]

Hi Charles,

Not quite correct. Take 1000 Birds!  
Hold any Key!

Code: [Select]

indexbase 0
include "window.h"
Finit

SetWindow "Birds",800,600,w_1
SetFont 12,12,0,""

While WinExit=0
cls 0
For jx=0 To 1000
SetText "*", Rand(0,1800) /Log(10),Rand(0,1400) /Log(10), RGB(Rand(64,255),Rand(64,255),Rand(64,255))
Next
Pause

DoEvents
SwapBuffers
Wend

WinEnd


[Charles Pegge]

Logarithms run to over 100 cpu clocks Peter

Any ideas about what a Maths.inc should contain? I suggest a few seminal procedures rather than trying to cover all possibilities.

Charles

[Peter]

yes,  Vector arithmetics!   

[Aurel]

Well i even don't know that there is no RND(x) in oxygen.
I would like to see hash table,linked list also in core

[Charles Pegge]

I'm developing a hash class. It is quite a bulky item (200 lines), so I will keep it separate from the Maths.

You can find it in src/HashStore.o2bas

Here is the hash encoder:

Code: [Select]

 '-------------------------------
  method hashcode(string s) as sys
  '===============================
  xor eax,eax
  mov edx, [s]     ' name pointer
  mov ecx, [edx-4] ' length
  (
  cmp ecx,0
  jnz exit
  return 0 'EMPTY WORD WILL TRIGGER HASHCODE ERROR LATER
  )
  mov ah,  cl      ' assume max length 255
  mov al,  [edx]   ' 1st letter
  cmp cl,1
  (
    jz exit
    shl eax,3
    xor al,  [edx+1] ' 2nd letter
    shl eax,3
    (
      rol eax,1
      xor al, [edx]
      inc edx
      dec ecx
      jnz repeat
    )
  )
  return eax
  '
  end method

Charles

[Aurel]

Great...

[Peter]

Hi Charles,

something  Maths for Maths.inc

Code: [Select]

Function sgn (Single a) as single                 'sign
  single sgn
  iF a < 0 
     sgn= -1
  Else 
     sgn = 1
  End iF
Return sgn
End Function

Function Sec(single x) as single                    'Secant
Return 1 / Cos(x)
End Function

Function CoSec(single x) as single                  'CoSecant         
Return 1 / Sin(x)
End Function

Function CoTan(single x) as single                   'CoTangent 
Return 1 / Tan(x)
End Function

Function ArcSin(single x) as single                  'Inverse Sine
Return Atn(x / Sqr(-x*x+1))
End Function

Function ArcCos(single x) as single                  'Inverse Cosine
Return Atn(-x / Sqr(-x*x+1))+2*Atn(1)
End Function

Function ArcSec(single x) as single
Return Atn(x / Sqr(x*x-1))+Sgn((x)-1)*(2* Atn(1))  'Inverse Secant
End Function

Function HSin(single x) as single                    'Hyperbolic Sine
Return (Exp(x)-Exp(-x)) /2
End Function

Function HCos(single x) as single                    'Hyperbolic Cosine
Return (Exp(x) + Exp(-x)) /2
End Function

Function HTan(single x) as single                    'Hyperbolic Tangent
Return (Exp(x)-Exp(-x)) / (Exp(x)+Exp(-x))
End Function