FPU example with accuracy up to 8 digits

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CampTheBoss

Joined: 02 Feb 2015
Posts: 42
Location: A chair

CampTheBoss 10 Mar 2015, 18:53

Hey, it's me. I just want to show you the latest project I have done; I used the FPU to calculate division up to 8 digits. Here is the source if you want to have a look at it.

Code:

format PE console 6.0
include 'win32a.inc'
entry start

section '.data' data readable writeable
format_f db "%2.8f",10,0
val1 dd 1,0
val2 dd 4,0
decnum dd 1110000.0,0
decnum2 dd 0.2,0
divnum dd 1000000.0,0

section '.text' code readable executable
start:
push 5
finit
fild dword[esp]
fiadd dword[val1]
fst st1
fmul st0,st1
fiadd dword[val2]
fmul st0,st0
fadd dword[decnum]
fadd dword[decnum2]
fdiv dword[divnum]
fnop    ;Mnemonic for "FPU no operation"
sub esp,4
fstp qword[esp]
push format_f
call [printf]
invoke ExitProcess,0

section '.idata' import data readable
library msvcrt,'msvcrt.dll',\
        kernel,'kernel32.dll'

import msvcrt,\
       printf,'printf'

import kernel,\
       ExitProcess,'ExitProcess'

If there is anything i should improve, give me feedback Smile

10 Mar 2015, 18:53

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20630
Location: In your JS exploiting you and your system

revolution 11 Mar 2015, 01:10

One thing to note about single precision floating point numbers in IEEE754 format is that they don't provide 8 digits of precision. The most you can achieve is 7 decimal digits because the mantissa is only 23+1 bits.

Also, what is the purpose of the fnop?

11 Mar 2015, 01:10

CampTheBoss

Joined: 02 Feb 2015
Posts: 42
Location: A chair

CampTheBoss 11 Mar 2015, 20:11

aah is that why i always get a '15' for no reason? First about the single precision floating-point thing: i use over 8 digits so i can see the whole result, I have already read about the FPU and know about that Razz

. about the fnop.. I just put it in for no reason o.o

11 Mar 2015, 20:11

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