Re: long double data type
Re: long double data type
- Subject: Re: long double data type
- From: Stephen Davis <email@hidden>
- Date: Tue, 15 Jun 2010 13:15:08 -0700
On Jun 15, 2010, at 10:44 AM, Luigi Castelli wrote:
> Hi there,
>
> this is the second time that I get a similar response:
>
>> Are you sure that your DSP approach is sound?
>>
>> If 64bits are not enough there is probably something wrong
>> with your algorithm.
>
> I really don't want to sound arrogant because it is not what I am about, however I ASSURE you that I performed all the necessary tests, both mathematical and auditive to corroborate my conclusion. My approach is sound, I just don't have enough bits for the audio quality I am after. I understand it might sound weird to hear that 64 bits are not enough.
> I might have reached the upper limit of the current technology, but doubting my approach is not helping. I would ask advice on the approach if I wasn't sure it was the right one.
>
> I would love to get back on track with the questions I have asked.
> I apologize in advance if I offended somebody. It was not my intention.
>
> Thank you for your understanding.
>
> - Luigi
Tahome, personally I found your comment a bit rude and a non-answer to the original question. To paraphrase the old adage, "If you don't have anything useful to add, don't say anything." Let's keep the responses in the helpful category, not in the flame-bait category.
From "man float":
"On Intel macs, the type long double corresponds to IEEE-754 double extended precision. A double extended number is represented in 80 bits, and has a precision of 64 significant bits, roughly like 19 significant decimal digits. 15 bits are used to encode the exponent, which gives an exponent range from -16383 to 16384, inclusive."
This is a direct mapping to the x86 (technically x87) FPU hardware which has always been 80 bits. Note that, on Mac OS X (intel) systems, single and double precision floating point math is normally executed in the SSE unit, not the x87 FPU.
hth,
stephen
>
>
> --- On Tue, 6/15/10, tahome izwah <email@hidden> wrote:
>
>> From: tahome izwah <email@hidden>
>> Subject: Re: long double data type
>> To: email@hidden
>> Date: Tuesday, June 15, 2010, 8:33 AM
>> I know that I am not really
>> contributing, but...
>>
>>> (Yes, I did my tests and 64 bits of precision just
>> doesn't cut it)
>>
>> Are you sure that your DSP approach is sound?
>>
>> If 64bits are not enough there is probably something wrong
>> with your algorithm.
>>
>> Just my 2 centibits
>> --th
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>
>
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