J3/97-241
Date: 15 October 1997
To: J3
From: Larry Rolison
Subject: Interpretation Request: Value Returned by
SELECTED_REAL_KIND
NUMBER: 5
TITLE: Value returned by SELECTED_REAL_KIND
KEYWORDS: SELECTED_REAL_KIND
DEFECT TYPE: Interpretation
STATUS: X3J3 consideration in progress
QUESTION:
The SELECTED_REAL_KIND intrinsic function does not appear to cover one
specific case for real data types. Consider the following precisions
and ranges for a particular model:
KIND TYPE PRECISION RANGE
4 6 37
8 15 307
16 31 291
A test case for a system with this model is:
PRINT *, 'selrealkind(31,291) = ', SELECTED_REAL_KIND(P=31,R=291)
PRINT *, 'selrealkind(31,292) = ', SELECTED_REAL_KIND(P=31,R=292)
PRINT *, 'selrealkind(32,291) = ', SELECTED_REAL_KIND(P=32,R=291)
PRINT *, 'selrealkind(32,292) = ', SELECTED_REAL_KIND(P=32,R=292)
END
The Result Value section of the description of SELECTED_REAL_KIND clearly
describes the result value when the values of P and R are within the ranges
specified for the given implementation of the real data type model. It
further describes the values to be returned by SELECTED_REAL_KIND when a
value of P or R is not within the range of model numbers specified by the
implementation. From the text in the Result Value section, the following
may be determined:
* The reference to SELECTED_REAL_KIND(P=31,R=291) (first PRINT line) should
return the (kind type parameter) value 16.
* The third and fourth SELECTED_REAL_KIND references should return -1 since
the PRECISION argument is outside the set of allowed precision values.
However, the value returned by the second reference to SELECTED_REAL_KIND is
unknown since it does not appear to be covered by the wording of the Result
Value paragraph of section 13.14.95.
1. What should the processor return for the value of the
SELECTED_REAL_KIND intrinsic function when it does not have a single
data type that satisfies both the P and R values?
2. In particular, given the precision and range values shown above, what
should the processor return for the last three invocations of the
SELECTED_REAL_KIND intrinsic function?
ANSWER:
EDITS:
SUBMITTED BY: Larry Rolison / Joanne Brixius
HISTORY: J3/97-241 m143 submitted
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Larry Rolison lrr@cray.com
Cray Research, A Silicon Graphics Company
655F Lone Oak Drive
Eagan, MN 55121
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