| R.W. Hamming on Round-Off
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25 Sep 04 |
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Sven C. Koehler has started to read "Numerical Methods for Scientists
and Engineers". He was so kind to send me a few quotes he likes from
the introduction.
Most books on computing stress the estimation of roundoff,
especially the bounding of roundoff, but we shall concentrate
on the avoidance of roundoff. It seems better to avoid roundoff
than to estimate what did not have to occur if common sense and
few simple rules had been followed before the problem was put on
the machine.
Another standard algorithmic problem both in mathematics and in the use
of computation to solve problems is the solution of simultaneous linear
equations. Unfortunately much of what is commonly taught is usually not
relevant to the problem as it occurs in practice; nor is any completely
statisfactory method of solution known at present. Because the solution
of simultaneous linear equations is so often a standard library package
supplied by the computing center and because the corresponding
description is so often misleading, it is necessary to discuss the
limitations (and often the plain foolishness) of the method used by the
package. Thus it is necessary to examine carefully the obvious flaws and
limitations, rather than pretending they do not exist.
update: (sorry, German only;) A big thanks to Sven C. Koehler for this
summary
Ich habe es nun in den groessten Teilen ueberflogen. Die Ideen sind nicht
wirklich neu: Umformen von Gleichungen, Vermeiden ungefaehr gleichgrosse
Zahlen von einander abzuziehen, Approximation. Beim Loesen von
Gleichungssystemen schlägt er z.B. vor, ein Verfahren einzusetzen, das
kein wiederholtes Dividieren benoetigt, dann wird's auch nicht ungenau.
Trotzdem mag ich das Buch, weil es in mir den Eindruck weckt, dass es
sehr fundiert ist. Es ist voll von mathematischen Formeln, die ich alle
nicht wirklich verstanden habe, aber ich werde in jedem Fall wieder darin
nach Erklaerungen suchen, wenn ich mal wieder ein Numerik-Problem habe.
Ich glaube für dich ist as Buch eher langweilig, das meiste kennst du
bestimmt aus dem Studium. :-)
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| Good to know: Offline NT Password & Registry Editor, Bootdisk / CD
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25 Sep 04 |
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I’ve put together a single floppy or CD which contains things needed
to edit the passwords on most systems.
The bootdisk supports standard (dual)IDE controllers, and most
SCSI-controllers with the drivers supplied in a seperate archive below. It
does not need any other special hardware, it will run on 486 or higher,
with at least 32MB (I think) ram or more. Unsupported hardware: MCA, EISA,
i2o may not work. Some newer IDE/SCSI-raid systems may not work either.
Tested on: NT 3.51, NT 4, Windows 2000 (except datacenter?), Windows XP
(all versions), Window Server 2003 (at least Enterprise).
DANGER WILL ROBINSON! If used on users that have EFS encrypted files, and
the system is XP or later service packs on win2k, all encrypted files for
that user will be UNREADABLE! and cannot be recovered unless you remember
the old password again
link
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| This I believe! - Tom's 60 TIBs
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25 Sep 04 |
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Tom Peters is back with more Big Ideas for your job, your company, and your
life. The marketing and strategy guru holds forth on why audacity matters,
why women are the future of leadership, and why diversity is crucial to
business success. Those who have never read Tom will find an excellent
primer here; those well-versed in Peters’ ideas can get up to speed
on his latest thoughts. link direct pdf download
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| Simple things ..
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25 Sep 04 |
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I was just now doing some research on bus ticket clearing houses and I came
across his post in rec.travel.europe from 2001 by Michael Forrest.
>Reciprocity is not guaranteed on airlines (or toll bridges - it
>has always amused me that the toll on the Severn Bridge between
>England and Wales is GBP 4.20 for a car to enter Wales but there
>is no toll the other way, ie entering England). (Maybe it shows
>how the two countries value themselves?)
All of the bridges in the San Francisco Bay area only charge toll in one
direction. Some genius realized that, on the average, just about as many
cars went each way for the obvious reason that most trips across the
bridges are round trips. So they doubled the toll and took down the toll
booths going one way (except for the Golden Gate Bridge where the toll
booths remain, unattended). There has been considerable saving in toll
collection costs and the toll booth traffic jams in one direction are gone.
Is it possible the Severn Bridge does similarly?
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| Forth "versus" Whatever
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25 Sep 04 |
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From comp.lang.forth
>>Which brings me to an excellent 'forthism' I once read in a
>> newsletter. It stated:
>>
>> "You can do anything in Forth - but you must be prepared
>> to do it yourself."
In a recent discussion in c.l.functional, about why popular languages
are popular, I summarized the relationship between Lisp and Forth
more-or-less as follows:
"From the Lisper's perspective, every other language is a cute subset
of lisp; whereas from the Forther's perspective, every other language
is a cute extension of Forth."
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| My LinuxTag 2004 photos
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25 Sep 04 |
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Some photos from LinuxTag 2004 in Karlsruhe. I especially liked the Xbox
booting Linux screenshots. pics
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| Skolelinux: V1.0 with codename Venus is out! |
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25 Sep 04 |
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Skolelinux is made as free (as in speech) software, and is an overall computer solution based on school's resources and needs. It is based on Debian and runs very well on older hardware, too.
- Skolelinux is a network architecture tailored for use in schools.
- Skolelinux is designed to be easy and cheap to maintain.
- Skolelinux gives the students their own usernames, home directories and services.
- Skolelinux includes OpenOffice.org
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| RubyX
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25 Sep 04 |
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I just now came across the rubyx website
and noticed the logo. Nice!
Rubyx is a Linux-distribution similar to Gentoo, but all based on one ruby
script :-).
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| screen -x for remote pairprogramming
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25 Sep 04 |
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This tiny tool is great to have 2 people look and type into the same shell
window. Works great with vim :-)
- Both ssh or telnet into the same (remote) Unix machine and account.
- One enters screen, then starts vim, then the other enters screen -x.
- ctrl-d to exit screen)
Linux Gazette article about screen
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| Knoppix remastering mini-howto
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25 Sep 04 |
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(Source: Daniel Stirnimann) This mini howto shows how you can easily make
on your own customized knoppix build. Apart from that, there are a few
working methods described which make doing changes conveniently. The howto
is intended for people who work occasionaly on their builds.
link
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| Wine-Migration
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25 Sep 04 |
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At Linuxtag in Karlsruhe I met during lunch one of the authors of ganymede. I am the last person in the
world to promote the use of the Win32-API, but it can come in handy, when
you have to use some legacy software on Linux and do not want to pay
license fees for the usual suspects like vmware. Having to maintain only
one code-base is sexy, too.
I asked David Guembel, one of the fathers of the software to email me a
short describtion:
On an abstract level, the idea behind our ganymede system is simple: To make
an application run under Wine (a free Win32-API layer and Windows
executable loader), it is neccessary to know what parts of the Windows API
are actually required by that particular piece of software. Software has a
modular structure - in this context, a module is a Windows executable
(.DLL, .EXE, .OCX etc.) - and every module provides (exports) certain
functionality and requires (imports) functionality from other modules.
Thus, ganymede internally creates a dependency graph of an application's
binaries. This method is static and does not require anything but a fresh
installation of the software to be analyzed.
Before x-raying a Windows application, ganymede parses and stores an
analysis of the soure code of one or more Wine versions. It automagically
determines the implementation state of the APIs provided by Wine. During a
software analysis, the functionality required by the Windows application is
compared to what Wine provides, and missing or incomplete APIs are
reported. By storing Wine versions and the dependency structure of the
analyzed applications in a database, automatic or manual re-analysis with
different Wine versions is possible. Via the API ganymede itself provides,
the collected data is accessible in several ways. One application of that
API is our tool named sysiphus, which uses ganymede and a GUI-based
approach to semi-automatically determine the best possible Wine
configuration while providing for the possibility to re-use already
licensed Windows DLLs to fill the gaps Wine still leaves.
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| The Linux Incompatability List
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25 Sep 04 |
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Saw this on /.
"The Linux Incompatibility list is
a wiki project that attempts to document hardware that is incompatible with
Linux rather than list what is compatible. In the wiki, it is possible to
add alternitives so as to push hardware manufacturers to make good binary
drivers, publish specifications, or even better, publish open
drivers."
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| Big Requirements Up Front (BRUF)
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25 Sep 04 |
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I really appreciate Georg Tuparev’s postings to the XP-ML.
>Because it is important for the customer to have an idea of how much
>> everything will cost ...
In 99% of the times customer neither needs nor wants "everything"! One
of the big dangers of BRUF is that it imposes the wrong feeling that
"everything" is important. This is a major distraction that inevitably
leads to scope-creep and eventually project failures. When we have the
first meeting with a new customer we ask the following 3 questions:
1. What is your biggest pain?
2. If we solve this and only this pain, will your life get better?
3. Are you willing to pay X amount of Euros to us to solve this pain.
If any of these questions is answered with "no" we just thank for the
coffee and walk away. If all 3 questions are answered with yes, we move
to the first planning game...
Put it in another way: I do believe it is extremely dishonest and
incorrect behavior to conduct 9 months BRUF only to reach the
conclusion that the customer does not have enough resources to
continue. It is dishonest because as I wrote in an earlier posting,
_all_ good developers I know are able to estimate almost immediately
the scale of any software project without conducting BRUF.
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| Case stories
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25 Sep 04 |
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Been skimming the XP-ML this morning.
About the $200M Oracle-Ford Desaster: the management did not give them
enough power to go fully agile
Chet Hendrickson:
It was a very frustrating situation. The team asked Don and me
to help with preventing the Oracle consutants from making changes
directly to the production system. This was about $150 million into the project.
We tried to sell them on a more agile approach (as you might imagine), but by
this time they were pretty far gone.
It was unfortunante that we were not operating at a level in the organization
that would have allowed us to get the plug pulled sooner.
chet
Georg Tuparev has a nice case story, too: speak out if you are put on a
death march.
Few years ago I was called to lead a huge team stuck in one and half
year design phase. The team was supposed to build a control software
for a network of telecom satellites. Cannot disclosed names and
resources, but one could imagine ...
Three days in the project I had a phone conference with the CxO's of
both companies involved. Told them that the way it is going no
satellite will ever fly and that I know a better way. After getting
green line, the design document was burned with a small celebration at
a BBQ, and 85% of the initial team members were sent to an indefinitely
long vacation. With the rest (15%) of the team we had the first
functioning version 2 months ahead of the schedule and 50% lower then
expected expenses.
So the lessons:
- it is never late to change direction of a project in order to save it.
- I do not agree with Kent that this is a sad story. If you are a good
programmer put on a death march project you should speak out! If no one
listens - walk away. There is just one very precious life in front of
us - do not waste it! And if these folks wasted 2 years of their lives,
well, it is their business ... but they should not expect my
sympathies.
BTW, Philip is right - the project I was telling about had a 9 months x
40 people "Big Requirements Up Front"!!! Then the design started...
Just my 0.02
Georg Tuparev
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| .. like Xmas
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25 Sep 04 |
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I came across this nice discussion between Phlip and Juergen Ahthing in the
XP-ML
"Without test-first and refactoring, clients think
they must assemble as many program requirements as
they can afford to have written. This effort snarls
all relative business priorities together, making
Scope Control impossible. It obscures opportunities
for simplification. Designing and implementing many
features all at once is very hard, leading to our
industry's reputation for very large failures. Putting
tests in front of development's inner cycle permits an
outer cycle of incremental feature growth. That
relieves the Customer of the responsibility to predict
the future and guess which complete set of features
will maximize productivity."
.. Juergens answer:
Nice description.
Sometimes I try to explain that to non technical people
with the following picture:
If you have only one chance to get your wishes on a
list, it is like Christmas for a child. You make sure
you get every little wish on that list and hope for the best.
If you are sure that you can get your wishes on the list
at any time. You will just put the most important ones
there which come to your mind easily.
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| CIO magazine current issue all about agile... (IT oriented, but)
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25 Sep 04 |
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Denis Haskin posted this to the XP-ML. lnik
I assume this popped up on everyone else's RSS aggregator as well, but...
From Darrell Norton's blog [1] and Artima developer forum [2]: the
current issue of CIO magazine is all about agility:
http://www.cio.com/archive/081504/index.html
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| Hang the code, and hang the rules
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25 Sep 04 |
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Douglas Seelinger posted this in the XP-list:
A quote from "Pirates of the Caribbean: The Curse of the Black Pearl":
--You're pirates. Hang the code, and hang the rules. They're more like
guidelines anyway.
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| [XP] Alistair interview on IT Conversations
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25 Sep 04 |
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I was just sent the link for an online interview about agile development.
The interview was done last month, it got posted yesterday. You don’t
have to register to listen
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| [XP] RSS for Xprogramming blog
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25 Sep 04 |
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| What is XP?
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25 Sep 04 |
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Ron Jeffries posted this well known Kent Beck quote in the XP-mailinglist.
They talk about the 2nd ed. of XP Explained by Kent Beck.
But anyway, when I last asked Kent what XP is, he said
"XP is a community of software development practices based on
values of simplicity, communication, feedback, and courage".
That was about two or three years ago.
I look forward to seeing the second edition as well.
I'm sure it will be enlightening ...
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