Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Floating point error in C
Top Forums Programming Floating point error in C Post 302100690 by Perderabo on Thursday 21st of December 2006 01:48:14 PM
Old 12-21-2006
Floating point numbers have a complex representation using base 2 rather than base 10. Scientific notation is close enough to understand what is happening. With scientific notation, we want a number between 1 and 10 multiplied by a power of 10: 8080.9940 = 8.0809940 * 10^3 and we can check that out with bc:
Code:
$ bc
bc 1.03 (Nov 2, 1994)
Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
8.0809940 * 10^3
8080.9940000
^D$

But now we need to do that in binary... We want a number between 1 and 10 in binary (which means 1 and 2 in decimal) that can be multiplied by a power of 10 in binary to yield the decimal number 8080.9940. Fortunately, you picked an easy number! It's is obvious that dividing it by 4096 will yield a number between 1 and 2. So let's use bc to do this...
Code:
$ bc -l
bc 1.03 (Nov 2, 1994)
Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
obase=2
scale=40
8080.9940/4096
1.111110010000111111100111011011001000101101000011100101011000000100\
0001100010010011011101001011110001101010011111101111100111011011001
l(4096)/l(2)
1100.000000000000000000000000000000000000000000000000000000000000000\
00000000000000000000000000000000000000000000000000000000000000000000\
00
obase=10
ibase=2
1.1111100100001111111001110110110010001011010000 * 10^1100
8080.9939999999478459358215332031250000000000000000
1.11111001000011111110011101101100100 * 10^1100
8080.99399995803833007812500000000000000

Now repeat the last operation, but replace 1.11111001000011111110011101101100100 with some other close-by binary number. No matter what you try, you cannot get exactly 8080.9940 Floating point numbers are bit more complex than this, but the exact same issue arises with them. There is no way to exactly represent 8080.9940 as a floating point number.
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Floating Point Division

Does anyone have a simple way of doing floating point ("fp") division? For example, if I divide 3 by 5, I can get 0.6. The built-in calc (`bc`) will perform fp multiplication, but not division, at least not straight-up (i.e., starting bc and just typing in 3/5). I am trying to do this using... (1 Reply)
Discussion started by: gsatch
1 Replies

2. Shell Programming and Scripting

floating point addition

hi, :) I have a file like this 10.456 123.567 456.876 234.987 ........ ....... What i want to do is ia have to add all those numbers and put the result in some other file. Any help pls. cheers RRK (8 Replies)
Discussion started by: ravi raj kumar
8 Replies

3. Programming

floating point problem

Hi all! Hi all! I am working with a problem to find the smallest floating point number that can be represented. I am going in a loop ,stating with an initial value of 1.0 and then diving it by 10 each time thru the loop. So the first time I am getting o.1 which I wanted.But from the next... (4 Replies)
Discussion started by: vijlak
4 Replies

4. Linux

Floating Point Exception

Hi, I am compiling "HelloWorld" C progam on 32-bit CentOS and i want to execute it on 64-bit CentOS architecture. For that i copied the a.out file from 32-bit to 64-bit machine, but while executing a.out file on 64bit machine I am getting "Floating point exception error". But we can run... (3 Replies)
Discussion started by: Mandar123
3 Replies

5. UNIX for Dummies Questions & Answers

floating point error in linux + C

Here's a program and its pretty simple .It requires file handling and some calculations but on running it I am not getting the required result.It seems that the code outside the file read's outer while loop is not executing e.g the print statement is not being printed.Plz Help! #include<stdio.h>... (1 Reply)
Discussion started by: headrush
1 Replies

6. Shell Programming and Scripting

how to compare 2 floating point no.

Hi, Could any one tell me how to compare to floating point no. using test command. As -eq option works on only intergers. i=5.4 if then echo "equal" else echo "not equal" fi here output will be equal even though no. are unequal. Thanks, ravi (1 Reply)
Discussion started by: useless79
1 Replies

7. Shell Programming and Scripting

floating point numbers in if

# if > then > echo "1" > else > echo "2" > fi -bash: How can i compare floating point numbers inside statement? (15 Replies)
Discussion started by: proactiveaditya
15 Replies

8. Shell Programming and Scripting

Arithmetic in floating point

is it not possible to simply di aritmetic without using bc or awk i have tried folllowing operatrions but they support only integer types plz suggest me code for floating using values stored in the variables.the ans i get is integer and if i input floating values i get error numeric constant... (6 Replies)
Discussion started by: sumit the cool
6 Replies

9. Programming

Floating Point

Anyone help me i cant found the error of floating point if needed, i added the code complete #include <stdio.h> #include <string.h> #include <stdlib.h> #include <ctype.h> typedef struct { int hh; int mm; int ss; char nom; int punt; }cancion; typedef struct... (9 Replies)
Discussion started by: Slasho
9 Replies

10. Shell Programming and Scripting

floating point arithmetic operation error

I am writing a script in zsh shell, it fetchs a number from a file using the awk command, store it as a variable, which in my case is a small number 0.62000. I want to change this number by multiplying it by 1000 to become 620.0 using the command in the script var2=$((var1*1000)) trouble is... (2 Replies)
Discussion started by: piynik
2 Replies

LEARN ABOUT DEBIAN

httest

HTTEST(1)							   User Commands							 HTTEST(1)

NAME

       httest - test HTTP driven application

SYNOPSIS

       httest [OPTIONS] scripts

DESCRIPTION

       httest  is  a script based tool for testing and benchmarking web applications, web servers, proxy servers and web browsers. httest can emu-
       late clients and servers in the same test script, very useful for testing proxys.

OPTIONS

       -V --version
	      Print version number and exit

       -h --help
	      Display usage information (this message)

       -n --suppress
	      do no print start and OK|FAILED

       -s --silent
	      silent mode

       -e --error
	      log level error

       -w --warn
	      log level warn

       -i --info
	      log level info

       -d --debug
	      log level debug for script debugging

       -p --debug-system
	      log level debug-system to log more details

       -L --list-commands
	      List all available script commands

       -C --help-command
	      Print help for specific command

       -t --duration
	      Print test duration

       -T --timestamp
	      Time stamp on every run

       -S --shell
	      Shell mode

       -S --shell
	      Shell mode

       -D --define
	      Define variables

EXAMPLES

       httest script.htt

       httest -Ts script.htt

SCRIPTS

       httest is script based. The following script examples can be but into a scripte i.e. sample.htt and can be called like

       httest sample.htt

SIMPLE SCRIPT

       Get a page and do expect return code 200 OK.

       CLIENT
       _REQ www.google.ch 80
       __GET /search?q=apache HTTP/1.1
       __Host: www.google.ch
       __
       _EXPECT headers "HTTP/1.1 200 OK"
       _WAIT
       END

CUT AND PAST SCRIPT

       Cut and past from a HTTP stream, i.e we cut the apache host to access it in the second request.

       CLIENT
       _REQ www.google.ch 80
       __GET /search?q=apache HTTP/1.1
       __Host: www.google.ch
       __
       _MATCH body '<a href="http://([^/]*)/" class=l>Welcome! - The <em>Apache</em> HTTP Server Project' APACHE_HOST
       _WAIT

       _REQ $APACHE_HOST 80
       __GET / HTTP/1.1
       __Host: $APACHE_HOST
       __
       _WAIT
       END

CLIENT SERVER SCRIPT

       We can hold client and server in the same host. Actually multiple client and multiple server.  Very useful to test forward or reverse prox-
       ies. Or a webapplication which communicat itself with third party servers i.e. mail server.

       This is a very basic selfcontained test you can run on any maschine.

       CLIENT
       _REQ localhost 8080
       __GET /foo HTTP/1.1
       __Host: localhost
       __
       _WAIT
       END

       SERVER 8080
       _RES
       _EXPECT "/foo"
       _WAIT
       __HTTP/1.1 200 OK
       __Content-Length: AUTO
       __
       __Hello World
       END

SSL SCRIPT

       Of course SSL do also work with httest, just put "SSL:" before port.

       CLIENT
       _REQ localhost SSL:8080
       __GET /foo HTTP/1.1
       __Host: localhost
       __
       _WAIT
       END

       SERVER SSL:8080
       _RES
       _EXPECT "/foo"
       _WAIT
       __HTTP/1.1 200 OK
       __Content-Length: AUTO
       __
       __Hello World
       END

AUTHOR

       Written by Christian Liesch

REPORTING BUGS

       Report bugs to http://sourceforge.net/projects/htt

COPYRIGHT

       Copyright (C) 2006 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

httest 2.2.6							     June 2012								 HTTEST(1)
All times are GMT -4. The time now is 11:03 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy