; THIS CODE HAS NOT BEEN TESTED AND IS NOT FULLY OPERATIONAL.

; Problem Statement: Write 80387 ALP to obtain: i) Mean ii) Variance iii) Standard Deviation. Define the input values in data segment.

; Code from Microprocessor (SPPU - Second Year - Computer Engineering - Content) repository on KSKA Git: https://git.kska.io/sppu-se-comp-content/Microprocessor/


; BEGINNING OF CODE
%macro print 2
    mov rax,01
    mov rdi,01
    mov rsi,%1
    mov rdx,%2
    syscall
%endmacro


section .data
    m0 db 10,"------ Program to calculate mean, variance, standard deviation -----", 10
    l0:equ $-m0

    m1 db 10,"Mean is: "
    l1:equ $-m1

    m2 db 10,"Variance is: "
    l2:equ $-m2

    m3 db 10,"Standard Deviation is: "
    l3:equ $-m3

    m4 db 10,"Values are: 102.59, 198.21, 100.67"
    l4:equ $-m4

    dpoint db "."

    hdec dq 100

    num1 dd 102.59
    num2 dd 198.21
    num3 dd 100.67
    num4 dd 3.00

    newline db 0xa

section .bss

    dispbuff resb 1
    resbuff resb 10                 ;or we can also write resbuff rest 1
    mean resd 1
    variance resd 1


section .text

    global _start
    _start:
        print m0,l0
        print m4,l4

        finit                       ;initialize coprocessor
        fldz                        ;load stack top 0

    ;logic to calculate mean

    fld dword[num1]                 ;first number on x387
    fld dword[num2]

    fadd st0,st1

    fld dword[num3]
    fadd st0,st1

    fdiv dword[num4]                ;st0=add/3=mean
    fst dword[mean]

    print m1,l1

    call disp_result

    print newline,01                ;newline

    ;logic to calculate variance

    mov rsi,num1
    call cal_diff_sqr

    mov rsi,num2
    call cal_diff_sqr

    fadd st0,st1

    mov rsi,num3
    call cal_diff_sqr

    fadd st0,st1

    fdiv dword[num4]                ;divide by cardinality

    fst dword[variance]

    print m2,l2

    call disp_result

    print newline,01                 ;newline

    ;logic to calculate standard deviation

    fld dword[variance]
    fsqrt

    print m3,l3
    call disp_result

    print newline,01                 ;newline

    mov rax,60
    mov rdi,0
    syscall

 disp_result:
    fimul dword[hdec]
    fbstp [resbuff]                  ;store bcd and pop from top of the stack

    xor rcx,rcx                      ;clear rcx register
    mov rcx,09h
    mov rsi,resbuff+9                ;rsi pointing to msb of resultant

    up1:
    push rcx
    push rsi

    mov bl,[rsi]
    call disp8_proc

    print dispbuff,02
    pop rsi
    dec rsi
    pop rcx
    loop up1

    print dpoint,01

    mov bl,[resbuff]
    call disp8_proc

    print dispbuff,02

    ret

disp8_proc:
   mov rdi,dispbuff
   mov rcx,02

 back:
   rol bl,04
   mov dl,bl
   and dl,0Fh
   cmp dl,09h
   jbe skip
   add dl,07h

skip:
   add dl,30h
   mov [rdi],dl
   inc rdi
   loop back

   ret

cal_diff_sqr:
   fld dword[rsi]
   fsub dword[mean]
   fmul st0,st0
 ret
; END OF CODE