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Re: [avr-libc-dev] Pow Function in avr8
From: |
Georg-Johann Lay |
Subject: |
Re: [avr-libc-dev] Pow Function in avr8 |
Date: |
Thu, 29 Nov 2012 00:44:25 +0100 |
User-agent: |
Thunderbird 2.0.0.24 (Windows/20100228) |
Jan Waclawek schrieb:
Floating point equivalence is not guaranteed so is this comparison
valid ?
C99 in 5.2.4.2.2#5 says: The accuracy ofthe floating-point operations
(+, -, *, /) and of the library functions in <math.h>and <complex.h>
that return floating-point results is implementation-defined [...]
The implementation may state that the accuracy is unknown.
Which is the case, cf. [1]:
* The accuracy of the floating-point operations and of the library
functions in <math.h> and <complex.h> that return floating-point
results (C90 and C99 5.2.4.2.2).
The accuracy is unknown.
Which basically means precision is a matter of the target.
The (E)ABI of avr-gcc does not define floating point precision,
at least I don't know of it. Similar for AVR Libc.
PS. Are you sure you linked against avr-libc's math library?
FYI and in the case you refer to whether -lm is used or not:
That won't matter in new avr-gcc, cf. [2]
Johann
[1]
http://gcc.gnu.org/onlinedocs/gcc/Floating-point-implementation.html
[2]
http://gcc.gnu.org/PR54461
- [avr-libc-dev] Pow Function in avr8, Thomas, George, 2012/11/28
- Re: [avr-libc-dev] Pow Function in avr8, Jan Waclawek, 2012/11/28
- Re: [avr-libc-dev] Pow Function in avr8, Thomas, George, 2012/11/28
- Re: [avr-libc-dev] Pow Function in avr8, Jan Waclawek, 2012/11/28
- Re: [avr-libc-dev] Pow Function in avr8, Thomas, George, 2012/11/29
- Re: [avr-libc-dev] Pow Function in avr8, Georg-Johann Lay, 2012/11/29
- Re: [avr-libc-dev] Pow Function in avr8, Thomas, George, 2012/11/29
- Re: [avr-libc-dev] Pow Function in avr8, Georg-Johann Lay, 2012/11/29
Re: [avr-libc-dev] Pow Function in avr8,
Georg-Johann Lay <=
Re: [avr-libc-dev] Pow Function in avr8, Amine Najahi, 2012/11/28