Alexandre Torres Porres porres at gmail.com
Thu Jan 29 18:36:39 CET 2015

```> more that 7 digit but less than 8 digits
...
> so, 4/3 =! 1.33333
> but 4/3 == 1.33333333 (8 "3")

I don't get it. More than 7 decimal digits but less than 8 decimal digits?
How does that work? In practice, is it 7 or 8?

In the example we see that 4/3 == 1.33333333 (8 "3") - so it's 8 decimal
digits...

I have a work around using expr. Just put the number in parenthesis.

Try [expr 4./3 == (1.33333333)] (8 "3")

but the thing is that this is also true -  [expr 4./3 == (1.3333333)] - also
equal to 7 "3"

cheers

2015-01-29 14:58 GMT-02:00 Cyrille Henry <ch at chnry.net>:

> hello,
>
> ok, claude was faster to answer, but since i already write my mail, i send
> it anyway...
>
>
> pd internal resolution is float32.
> (i.e, 23 bit, so a bit less than 17 millions, i.e more that 7 digit but
> less than 8 digits)
> pd graphical representation is 6 digits
>
> so, 4/3 =! 1.33333 but 4/3 == 1.33333333 (8 "3")
> even if both are represented with the same number of 3...
> this is a generic problem of computer float.
>
> the only odd thing concerning pd is that number are also saved with 6
> digit.
> (so precision can be lost when a patch is saved)
>
> try the attachment patch.
> then save the patch, and open it back, and see that precision is lost.
> (I have to modifies the patch as text file to have this behaviors, but you
> can also have the save precision when creating an object... until you
>
> you can also have a look on the top right of the patch: a weird effect of
> float precision...
>
> cheers
> c
>
> Le 29/01/2015 17:17, Alexandre Torres Porres a écrit :
>
>> Well, thanks everyone.
>>
>> And now for some related issues.
>>
>> Pd can only represent up to 6 significant digits, so they say. For
>> example, in a message, you can have a number with up to 5 decimal places,
>> like: -5.29314e+12
>>
>> but it does have a better internal resolution, if you compare 4 / 3 to
>> 1.33333 you'll see 4 / 3 is higher ( try [expr 4./3 > 1.33333] and check).
>>
>> So, what's this internal resolution? And why can't you have the same
>> resolution in a message?
>>
>> thanks
>>
>> 2015-01-28 16:06 GMT-02:00 Martin Peach <chakekatzil at gmail.com <mailto:
>> chakekatzil at gmail.com>>:
>>
>>     On Wed, Jan 28, 2015 at 12:00 PM, Cyrille Henry <ch at chnry.net
>> <mailto:ch at chnry.net>> wrote:
>>
>>
>>
>>         Le 28/01/2015 17:47, Alexandre Torres Porres a écrit :
>>
>>               > it's a limitation of 32 bit float
>>
>>             I thought so, but same happens when I use the new Pd Vanilla
>> 64 bits...
>>
>>         this mean that it's compiled for 64 bit CPU, not that float are
>> store on 64 bits
>>
>>     Also last time I checked, Pd saves floats by first printing them to 6
>> digit precision, so they have even less range than a 'float' type.
>>     You could use an object made with pdlua to manipulate large
>> floating-point numbers, as there is no(?) limit to the size of a float in
>> lua.
>>
>>     Martin
>>
>>     _______________________________________________
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>>
>>
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