Efficiency of math.h

[E. Robert Tisdale]

Something that calls itself Mac wrote:

[snip]

Go away troll.

 

[E. Robert Tisdale]

Something that calls itself Mac wrote:

[snip]

Go away troll.

 

[Mac]

You also need to watch your back with Trollsdale around. ;-[

You need to get a job Chuck.
You spend too much time trolling in the comp.lang.c newsgroup.
If you can't get a job, retire and take up a real hobby
like fishing or card playing with the local cronies.

CBFalconer is, as far as I am concerned, a valuable poster in this
newsgroup. What's more, since he first appeared, he has shown that he can
respond to constructive criticism, and make an effort to fit in. I have
personally never seen him troll.

I am posting this for the benefit of any who might otherwise be persuaded
by E. Robert Tisdale's characterization of CBFalconer.

--Mac

 

[Mac]

It's perverse.


Not likely. Trolls never use kill files.
Their egos won't let them. They just threaten.

Hmmm. Mike Wahler is not a troll, either. What are you talking about?

[snip]

--Mac

 

[Mac]

Mr. E. Tisdale,

I have over 20 years experience with the C language and have
purposely avoided the math library. Most of the embedded systems
I worked would die (come to a hault) or worse if the math
library was included. But, from reading your past posts,
you either claim that embedded systems don't exist or
insuate that only desktop and the like exist.

In smaller embbeded applications, either a lookup table
is used (due to size and speed) or the numerical base
is changed so floating point is not required. Many
times, the accuracy is not required to move a solenoid.

I have learned calculus and numerical analysis. Just
because I don't use all the features of the language
doesn't make me a newbie.

Don't worry too much about E. Robert Tisdale. While I don't understand
what makes him tick, I am quite sure that he is disingenuous. Certainly
any accusation he makes will not be taken seriously by people who read
this newsgroup frequently.

--Mac

 

[E. Robert Tisdale]

Something that calls itself Mac wrote:

[snip]

Go away troll.

 

[Christian Bau]

I'm not the one claiming that I can beat the acos function
that came with my compiler's implementation of the standard library.
You are claiming that you can use interpolation
to beat the built-in acos function.
The burden of proof lies with you and not me.
I challenged to to demonstrate this and you failed.

That's the Troll's method: ALWAYS demand proof for any statement or
others, never provide proof for anything you post yourself. Always
demand, demand, demand. Never give anything of value yourself.

I challenged you: ?20,000 that I can beat ANY algorithm that you post.
You are free to accept. I've got the money, you can cash in your pension
from being a JPL janitor for 25 years. So what is stopping you?

 

[Christian Bau]

Something that calls itself Mac wrote:

[snip]

Go away troll.

You are trying to copy my "Tisdale, you are an idiot, go away" posts.

There is a difference though that readers of c.l.c will appreciate: They
have no reason whatsoever to believe that "Mac" is a troll. They know
for certain that you are an idiot.

 

[Christian Bau]

Ya, I'm back. The signal-to-noise ratio in this thread is getting pretty
small . In short, I don't know the exact accuracy that will be needed. I
am using the acos function do determine the angle between vectors, in order
to simulate angular spring torque in a numeric sumulation of elastic
surfaces. It's for non-scientific graphical simulation, and we do not have a
theoretically rigid physical model, so we can probably get away with some
approximation.

Since it is probably very simple to calculate the cosine of the angle,
and getting the angle is time consuming, you should consider whether you
need to know the angle at all or whether knowing the cosine is enough.

For example, for transformations in 3D space you never need to know the
angle itself, you are much better off knowing the cosine of the angle.
The same might apply to your problem; you might be able to do any
calculations without evaluating any trigonometric functions at all.

 

[Joona I Palaste]

You also need to watch your back with Trollsdale around. ;-[

You need to get a job Chuck.
You spend too much time trolling in the comp.lang.c newsgroup.
If you can't get a job, retire and take up a real hobby
like fishing or card playing with the local cronies.

CBFalconer is, as far as I am concerned, a valuable poster in this
newsgroup. What's more, since he first appeared, he has shown that he can
respond to constructive criticism, and make an effort to fit in. I have
personally never seen him troll.

I am posting this for the benefit of any who might otherwise be persuaded
by E. Robert Tisdale's characterization of CBFalconer.

Getting called a troll by Tisdale is a sign of great respect on this
newsgroup. Therefore I am still anxiously waiting the day when Tisdale
calls me a troll.

 

[goose]

So I have one semi-serious question for the NG, since I no longer feel sorry
for Tisdale... The FAQ is for frequently-asked-questions: is it possible to
add something to the FAQ about certain Trolls - since his knowledge is
frequently questioned? =)

Unfortunately, the typical response you are going to get to that
from the trolls mentioned in the FAQ is going to be along the
lines of

"<blush> I'm Famous!!!"


goose,
hand

 

[CBFalconer]

.... snip ...

For example, for transformations in 3D space you never need to
know the angle itself, you are much better off knowing the
cosine of the angle. The same might apply to your problem; you
might be able to do any calculations without evaluating any
trigonometric functions at all.

As another example, in 0 through pi/4 - epsilon, if you need only
a magnitude relationship between tan(x) and tan(y), you only need
to compare x and y. To replace atan computations, look at the
theta function in Sedgewicks Algorithms.

 

[Roc]

[snip]

Unfortunately, the typical response you are going to get to that
from the trolls mentioned in the FAQ is going to be along the
lines of

"<blush> I'm Famous!!!"

I'm thinking about the infrequent & new readers of the NG. Many of you
provide valuable, informative help with kids' homework assignments. If by
reading the FAQ they can avoid misinformation by avoiding certain Trolls,
wouldn't that offset the c.l.c worry of immortalizing said Troll(s)? Just
an idea... =)

 

[Richard Heathfield]

Roc wrote:

I'm thinking about the infrequent & new readers of the NG. Many of you
provide valuable, informative help with kids' homework assignments. If by
reading the FAQ they can avoid misinformation by avoiding certain Trolls,
wouldn't that offset the c.l.c worry of immortalizing said Troll(s)? Just
an idea... =)

Perhaps it would be more appropriate and useful to provide general
guidelines on how to identify good advice.

Although lots of people here call Tisdale a troll, I'm not actually sure
whether "troll" is the right word. He might just be stupid. It's hard to
tell. But, ideally, such guidelines as I suggest would deal with either
possibility, since neither trolls nor stupid people give good advice.

 

[Joona I Palaste]

Roc wrote:

Perhaps it would be more appropriate and useful to provide general
guidelines on how to identify good advice.

Although lots of people here call Tisdale a troll, I'm not actually sure
whether "troll" is the right word. He might just be stupid. It's hard to
tell. But, ideally, such guidelines as I suggest would deal with either
possibility, since neither trolls nor stupid people give good advice.

No, I cannot join this diagnosis. Trollsdale is not just stupid. He's
downright malicious.

 

[Grumble]

P.S. - the above formula, expanded, becomes
cos(n) * cos(acos(x)) ---

In which universe is cos(a*b) equal to cos(a)*cos(b) ?

 

[Dave Rudolf]

Another possibility is changing the internal representation of your
program from rectagular vectors to a polar form. Even using both in
different places of the program.

Interesting proposition, but there would be a lot of conversion going on. I
would have to do a lot of sines and cosines (or arc-tangents) so I don't
think that there would be much savings.

Dave

 

[Grumble]

I also did not put []'s around the word "interpolation."

Actually, You originally wrote "extrapolation". It was Tisdale who
changed "extrapolation" to "interpolation" when he modified your post.

 

[Default User]

Something that calls itself Mac wrote:

[snip]

Go away troll.

Can't handle the truth, huh Trollsdale. You've been busted on this habit
of changing people's quotes so much, it's become pretty obvious to even
the most kind-hearted that YOU are the troll. And one of the most
dishonest ones I've ever seen.

Changing quotes is one of the lowest things. If you had any shame (and
it's clear you don't) you'd be deeply ashamed of yourself.

Dry up and go away, you are a menance to proper learning of the C
language.



Brian Rodenborn

 

[Default User]

Although lots of people here call Tisdale a troll, I'm not actually sure
whether "troll" is the right word. He might just be stupid. It's hard to
tell. But, ideally, such guidelines as I suggest would deal with either
possibility, since neither trolls nor stupid people give good advice.

Sorry, I can't go along with that. His tactics of spreading
misinformation are too blatant to be put to simple ignorance. He is a
troll, pure and simple.



Brian Rodenborn