Cycling 74 » Topic: mtof cents detuning math flawed?

mtof cents detuning math flawed?

Ploki — Wed, 09 May 2012 13:52:19 +0000

It’s not really a big deal, i’m just curious whether my math is flawed or max’ math is flawed

– Pasted Max Patch, click to expand. –

Re: mtof cents detuning math flawed?

Christopher Dobrian — Wed, 09 May 2012 16:15:58 +0000

The example below shows the correct math, I think (assuming the U.S. standard of 440 Hz for A). There are very slight differences between the output of mtof and expr, but I’m guessing that that just has something to do with different implementations of the power function or something. The differences are pretty minuscule and should not be a problem in most cases (you have to stretch the flonum objects to be bigger in order to see the differences, which are on the order of a few 1/10,000ths of a Hz).

– Pasted Max Patch, click to expand. –

Re: mtof cents detuning math flawed?

nicolas danet — Wed, 09 May 2012 16:22:49 +0000

Hello,

computer math is flawed ?

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

Re: mtof cents detuning math flawed?

Ploki — Wed, 09 May 2012 18:11:47 +0000

lol :)

sorry. thank you both.

Re: mtof cents detuning math flawed?

Roman Thilenius — Thu, 10 May 2012 04:33:43 +0000

the mtof obejcts are using the “other” method, which is less accurate but faster.

Re: mtof cents detuning math flawed?

Peter Castine — Fri, 11 May 2012 08:24:23 +0000

If you take the trouble to look at mtof.maxhelp, you will see the formula that mtof actually uses.

The two [expr]s are mathematically equivalent to within the accuracy of 6 digits. Chris’ formula is more accurate because the exponent of the pow() function is always calculated to full 64-bit precision. The formula used by mtof is more efficient because the constant portion of the function is precalculated. A classic efficiency vs. accuracy trade-off.

So, show of hands, please: who can hear the difference of frequency?

Re: mtof cents detuning math flawed?

goodparleyandorfing — Fri, 11 May 2012 08:31:42 +0000

“If you take the trouble to look at mtof.maxhelp, you will see the formula that mtof actually uses.”

That’s not actually true anymore. The max6 help file no longer contains the expr solution.

“So, show of hands, please: who can hear the difference of frequency?”

La Monte Young!

Re: mtof cents detuning math flawed?

Roman Thilenius — Fri, 11 May 2012 09:40:12 +0000

peter: you can hear it when you mix the two methods in your patch, so it is good
to know about this difference, then decide which one to use.