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11-03-2005 09:32 PM
11-03-2005 09:32 PM
I've had a user come to me asking about whether Alpha has support for 128 bit floating point reals (H-floating on VAX).
Any help on this would be appreciated.
thanks
Neil
Solved! Go to Solution.
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11-03-2005 10:00 PM
11-03-2005 10:00 PM
Solutionhttp://h71000.www7.hp.com/doc/73final/documentation/pdf/OVMS_MIGR_APPL.pdf
H float is not supported. Consider using X float which is IEEE extended double precision and has a similar range. There are compiler qualifers (depending on the language used) to select this and conversion routines to convert to various formats.
VAX code translated to Alpha using DECmigration can use H Float.
Purely Personal Opinion
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11-03-2005 10:01 PM
11-03-2005 10:01 PM
Re: 128 bit floating point real
The FORTRAN compiler supports REAL*16.
On VAX processors, H_floating format is used to implement REAL*16. On Alpha processors, IEEE X_floating format is used to implement REAL*16.
Regards,
Kris (aka Qkcl)
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11-03-2005 10:05 PM
11-03-2005 10:05 PM
Re: 128 bit floating point real
create f128.for
program f128
* test if we have real*16
real*16 test
test=1.1234567899999999
print *, ' ',test
print *, ' ',test/test
end Exit
fortran f128.for
link f128
run f128
1.12345683574676513671875000000000
1.00000000000000000000000000000000
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11-03-2005 10:49 PM
11-03-2005 10:49 PM
Re: 128 bit floating point real
In addition on Alphas, the DOUBLE PRECISION (F90 REAL(KIND=16)) can be made by default 128 bit (X-floating), with the /DOUBLE_SIZE=128 Fortran compiler switch.
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11-03-2005 11:01 PM
11-03-2005 11:01 PM
Re: 128 bit floating point real
Unfortunately we're using ADA rather than Fortran, which doesn't have the X or H switches available. Does anyone have any thoughts on the ADA side?
Neil
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11-03-2005 11:44 PM
11-03-2005 11:44 PM
Re: 128 bit floating point real
AFAIK, on Alpha, the FORTRAN, the HP C, the HP Pascal compilers support 128-bit floating points (IEEE X_float); the ADA compiler does not.
Regards,
Kris (aka Qkcl)
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11-04-2005 02:09 AM
11-04-2005 02:09 AM
Re: 128 bit floating point real
Purely Personal Opinion
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11-04-2005 04:44 AM
11-04-2005 04:44 AM
Re: 128 bit floating point real
Neil
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11-04-2005 04:45 AM
11-04-2005 04:45 AM