Floating point is different for each platform. The test... well it is  
likely to not be exact.

On Aug 3, 2009, at 9:31 PM, Ross M. wrote:

> Public bug reported:
>
> differences in precision are causing func_math test to fail.  
> log(3,9) is
> expecting exactly 2, but on freebsd gets 2.0000000000000004440892.
>
> a simple program doing log(9) / log(3) produces the following on  
> linux, and
> freebsd:
>
> animal$ uname -a
> Linux animal 2.6.28-13-generic #45-Ubuntu SMP Tue Jun 30 22:12:12  
> UTC 2009 x86_64 GNU/Linux
> animal$ ./log
> 2.1972245773362195642164 / 1.0986122886681097821082 =  
> 2.0000000000000000000000
>
> rowlf$ uname -a
> FreeBSD rowlf.local 7.1-RELEASE FreeBSD 7.1-RELEASE #0: Thu Jan  1  
> 08:58:24 UTC 2009     <email address hidden>:/usr/obj/usr/src/ 
> sys/GENERIC  amd64
> rowlf$ ./log
> 2.1972245773362195642164 / 1.0986122886681095600636 =  
> 2.0000000000000004440892
>
> log(9) is identical on both systems, but log(3) differs after 15 or  
> 16 digits
> and the division of log(9) / log(3) effectively doubles that error.
>
> i'm at a loss as to how to address this one. it seems like the  
> freebsd log call
> can return data less accurately than linux, but i'm not sure it's  
> safe to assume
> that you have a full double's worth of precision in those sorts of  
> calculations.
> don't think there'll be a patch i can attach to this one without some
> discussion...
>
> - test failure
> -----------------------------------------------------------------
>
> main.func_math                 [ fail ]
>
> --- ../tests/r/func_math.result	2009-08-04 07:07:52.669905696 +0300
> +++ ../tests/r/func_math.reject	2009-08-04 07:15:33.773824490 +0300
> @@ -44,7 +44,7 @@
> Note	1003	select abs(-(10)) AS `abs(-10)`,sign(-(5)) AS  
> `sign(-5)`,sign(5) AS `sign(5)`,sign(0) AS `sign(0)`
> select  
> log 
> (exp 
> (10 
> )),exp 
> (log 
> (sqrt(10))*2),log(-1),log(NULL),log(1,1),log(3,9),log(-1,2),log(NULL, 
> 2);
> log(exp(10))	exp(log(sqrt(10))*2)	log(-1)	log(NULL)	log(1,1)	 
> log(3,9)	log(-1,2)	log(NULL,2)
> -10	10.000000000000002	NULL	NULL	NULL	2	NULL	NULL
> +10	10.000000000000002	NULL	NULL	NULL	2.0000000000000004	NULL	NULL
> Warnings:
> Error	1365	Division by 0
> Error	1365	Division by 0
>
> ** Affects: drizzle
>     Importance: Undecided
>         Status: New
>
>
> ** Tags: freebsd
>
> -- 
> main.func_math fails due to precision error
> https://bugs.launchpad.net/bugs/408694
> You received this bug notification because you are a member of  
> Drizzle-
> developers, which is subscribed to Drizzle.
>
> Status in A Lightweight SQL Database for Cloud and Web: New
>
> Bug description:
> differences in precision are causing func_math test to fail.  
> log(3,9) is
> expecting exactly 2, but on freebsd gets 2.0000000000000004440892.
>
> a simple program doing log(9) / log(3) produces the following on  
> linux, and
> freebsd:
>
> animal$ uname -a
> Linux animal 2.6.28-13-generic #45-Ubuntu SMP Tue Jun 30 22:12:12  
> UTC 2009 x86_64 GNU/Linux
> animal$ ./log
> 2.1972245773362195642164 / 1.0986122886681097821082 =  
> 2.0000000000000000000000
>
> rowlf$ uname -a
> FreeBSD rowlf.local 7.1-RELEASE FreeBSD 7.1-RELEASE #0: Thu Jan  1  
> 08:58:24 UTC 2009     <email address hidden>:/usr/obj/usr/src/ 
> sys/GENERIC  amd64
> rowlf$ ./log
> 2.1972245773362195642164 / 1.0986122886681095600636 =  
> 2.0000000000000004440892
>
> log(9) is identical on both systems, but log(3) differs after 15 or  
> 16 digits
> and the division of log(9) / log(3) effectively doubles that error.
>
> i'm at a loss as to how to address this one. it seems like the  
> freebsd log call
> can return data less accurately than linux, but i'm not sure it's  
> safe to assume
> that you have a full double's worth of precision in those sorts of  
> calculations.
> don't think there'll be a patch i can attach to this one without some
> discussion...
>
> - test failure  
> -----------------------------------------------------------------
>
> main.func_math                 [ fail ]
>
> --- ../tests/r/func_math.result	2009-08-04 07:07:52.669905696 +0300
> +++ ../tests/r/func_math.reject	2009-08-04 07:15:33.773824490 +0300
> @@ -44,7 +44,7 @@
> Note	1003	select abs(-(10)) AS `abs(-10)`,sign(-(5)) AS  
> `sign(-5)`,sign(5) AS `sign(5)`,sign(0) AS `sign(0)`
> select  
> log 
> (exp 
> (10 
> )),exp 
> (log 
> (sqrt(10))*2),log(-1),log(NULL),log(1,1),log(3,9),log(-1,2),log(NULL, 
> 2);
> log(exp(10))	exp(log(sqrt(10))*2)	log(-1)	log(NULL)	log(1,1)	 
> log(3,9)	log(-1,2)	log(NULL,2)
> -10	10.000000000000002	NULL	NULL	NULL	2	NULL	NULL
> +10	10.000000000000002	NULL	NULL	NULL	2.0000000000000004	NULL	NULL
> Warnings:
> Error	1365	Division by 0
> Error	1365	Division by 0