From 3be902cd0bdb566284ceb3f6fae538391da1faed Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Wed, 22 Dec 2010 16:07:08 +0100 Subject: [PATCH] ceil: Implement result sign according to IEEE 754. * lib/ceil.c (MIN, MINUS_ZERO): New macros. (FUNC): Return -0.0 for -1 < x < 0. * tests/test-ceil2.c: Include minus-zero.h. (MINUS_ZERO): New macro. (ceil_reference): Keep in sync with lib/ceil.c. * tests/test-ceilf2.c: Include minus-zero.h. (MINUS_ZERO): New macro. (ceilf_reference): Keep in sync with lib/ceil.c. * tests/test-ceilf-ieee.c (main): Test also values between -1 and 1. * tests/test-ceil-ieee.c (main): Likewise. * tests/test-ceill-ieee.c (main): Likewise. --- ChangeLog | 13 +++++++++++++ lib/ceil.c | 18 ++++++++++++++++-- tests/test-ceil-ieee.c | 11 +++++++++++ tests/test-ceil2.c | 10 +++++++++- tests/test-ceilf-ieee.c | 11 +++++++++++ tests/test-ceilf2.c | 10 +++++++++- tests/test-ceill-ieee.c | 11 +++++++++++ 7 files changed, 80 insertions(+), 4 deletions(-) diff --git a/ChangeLog b/ChangeLog index de2decf06..3c1cb7749 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,18 @@ 2010-12-22 Bruno Haible + ceil: Implement result sign according to IEEE 754. + * lib/ceil.c (MIN, MINUS_ZERO): New macros. + (FUNC): Return -0.0 for -1 < x < 0. + * tests/test-ceil2.c: Include minus-zero.h. + (MINUS_ZERO): New macro. + (ceil_reference): Keep in sync with lib/ceil.c. + * tests/test-ceilf2.c: Include minus-zero.h. + (MINUS_ZERO): New macro. + (ceilf_reference): Keep in sync with lib/ceil.c. + * tests/test-ceilf-ieee.c (main): Test also values between -1 and 1. + * tests/test-ceil-ieee.c (main): Likewise. + * tests/test-ceill-ieee.c (main): Likewise. + floor: Implement result sign according to IEEE 754. * lib/floor.c (FUNC): Return +0.0 for 0 < x < 1. * tests/test-floor2.c (floor_reference): Keep in sync with lib/floor.c. diff --git a/lib/ceil.c b/lib/ceil.c index 866804b18..2ed16540a 100644 --- a/lib/ceil.c +++ b/lib/ceil.c @@ -1,5 +1,5 @@ /* Round towards positive infinity. - Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc. + Copyright (C) 2007, 2010 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -27,19 +27,29 @@ # define FUNC ceill # define DOUBLE long double # define MANT_DIG LDBL_MANT_DIG +# define MIN LDBL_MIN # define L_(literal) literal##L #elif ! defined USE_FLOAT # define FUNC ceil # define DOUBLE double # define MANT_DIG DBL_MANT_DIG +# define MIN DBL_MIN # define L_(literal) literal #else /* defined USE_FLOAT */ # define FUNC ceilf # define DOUBLE float # define MANT_DIG FLT_MANT_DIG +# define MIN FLT_MIN # define L_(literal) literal##f #endif +/* -0.0. See minus-zero.h. */ +#if defined __hpux || defined __sgi || defined __ICC +# define MINUS_ZERO (-MIN * MIN) +#else +# define MINUS_ZERO L_(-0.0) +#endif + /* 2^(MANT_DIG-1). */ static const DOUBLE TWO_MANT_DIG = /* Assume MANT_DIG <= 5 * 31. @@ -78,8 +88,12 @@ FUNC (DOUBLE x) } else if (z < L_(0.0)) { + /* For -1 < x < 0, return -0.0 regardless of the current rounding + mode. */ + if (z > L_(-1.0)) + z = MINUS_ZERO; /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */ - if (z > - TWO_MANT_DIG) + else if (z > - TWO_MANT_DIG) { /* Round to the next integer (nearest or up or down, doesn't matter). */ z -= TWO_MANT_DIG; diff --git a/tests/test-ceil-ieee.c b/tests/test-ceil-ieee.c index 06cfeff9e..14ca3347f 100644 --- a/tests/test-ceil-ieee.c +++ b/tests/test-ceil-ieee.c @@ -24,9 +24,20 @@ int main () { + /* See IEEE 754, section 6.3: + "the sign of the result of the round floating-point number to + integral value operation is the sign of the operand. These rules + shall apply even when operands or results are zero or infinite." */ + /* Zero. */ ASSERT (!signbit (ceil (0.0))); ASSERT (!!signbit (ceil (minus_zerod)) == !!signbit (minus_zerod)); + /* Positive numbers. */ + ASSERT (!signbit (ceil (0.3))); + ASSERT (!signbit (ceil (0.7))); + /* Negative numbers. */ + ASSERT (!!signbit (ceil (-0.3)) == !!signbit (minus_zerod)); + ASSERT (!!signbit (ceil (-0.7)) == !!signbit (minus_zerod)); return 0; } diff --git a/tests/test-ceil2.c b/tests/test-ceil2.c index c26ccc340..74f8014c4 100644 --- a/tests/test-ceil2.c +++ b/tests/test-ceil2.c @@ -29,6 +29,7 @@ #include #include "isnand-nolibm.h" +#include "minus-zero.h" #include "macros.h" @@ -38,6 +39,9 @@ #define MANT_DIG DBL_MANT_DIG #define L_(literal) literal +/* -0.0. See minus-zero.h. */ +#define MINUS_ZERO minus_zerod + /* 2^(MANT_DIG-1). */ static const DOUBLE TWO_MANT_DIG = /* Assume MANT_DIG <= 5 * 31. @@ -79,8 +83,12 @@ ceil_reference (DOUBLE x) } else if (z < L_(0.0)) { + /* For -1 < x < 0, return -0.0 regardless of the current rounding + mode. */ + if (z > L_(-1.0)) + z = MINUS_ZERO; /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */ - if (z > - TWO_MANT_DIG) + else if (z > - TWO_MANT_DIG) { /* Round to the next integer (nearest or up or down, doesn't matter). */ z -= TWO_MANT_DIG; diff --git a/tests/test-ceilf-ieee.c b/tests/test-ceilf-ieee.c index 475e4f416..15a9fbf49 100644 --- a/tests/test-ceilf-ieee.c +++ b/tests/test-ceilf-ieee.c @@ -37,9 +37,20 @@ main (int argc, char **argv _GL_UNUSED) { float (*my_ceilf) (float) = argc ? ceilf : dummy; + /* See IEEE 754, section 6.3: + "the sign of the result of the round floating-point number to + integral value operation is the sign of the operand. These rules + shall apply even when operands or results are zero or infinite." */ + /* Zero. */ ASSERT (!signbit (my_ceilf (0.0f))); ASSERT (!!signbit (my_ceilf (minus_zerof)) == !!signbit (minus_zerof)); + /* Positive numbers. */ + ASSERT (!signbit (my_ceilf (0.3f))); + ASSERT (!signbit (my_ceilf (0.7f))); + /* Negative numbers. */ + ASSERT (!!signbit (my_ceilf (-0.3f)) == !!signbit (minus_zerof)); + ASSERT (!!signbit (my_ceilf (-0.7f)) == !!signbit (minus_zerof)); return 0; } diff --git a/tests/test-ceilf2.c b/tests/test-ceilf2.c index 3455cbf3e..b0893416b 100644 --- a/tests/test-ceilf2.c +++ b/tests/test-ceilf2.c @@ -29,6 +29,7 @@ #include #include "isnanf-nolibm.h" +#include "minus-zero.h" #include "macros.h" @@ -38,6 +39,9 @@ #define MANT_DIG FLT_MANT_DIG #define L_(literal) literal##f +/* -0.0. See minus-zero.h. */ +#define MINUS_ZERO minus_zerof + /* 2^(MANT_DIG-1). */ static const DOUBLE TWO_MANT_DIG = /* Assume MANT_DIG <= 5 * 31. @@ -79,8 +83,12 @@ ceilf_reference (DOUBLE x) } else if (z < L_(0.0)) { + /* For -1 < x < 0, return -0.0 regardless of the current rounding + mode. */ + if (z > L_(-1.0)) + z = MINUS_ZERO; /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */ - if (z > - TWO_MANT_DIG) + else if (z > - TWO_MANT_DIG) { /* Round to the next integer (nearest or up or down, doesn't matter). */ z -= TWO_MANT_DIG; diff --git a/tests/test-ceill-ieee.c b/tests/test-ceill-ieee.c index e7b541c83..0e06c0022 100644 --- a/tests/test-ceill-ieee.c +++ b/tests/test-ceill-ieee.c @@ -29,9 +29,20 @@ main () BEGIN_LONG_DOUBLE_ROUNDING (); + /* See IEEE 754, section 6.3: + "the sign of the result of the round floating-point number to + integral value operation is the sign of the operand. These rules + shall apply even when operands or results are zero or infinite." */ + /* Zero. */ ASSERT (!signbit (ceill (0.0L))); ASSERT (!!signbit (ceill (minus_zerol)) == !!signbit (minus_zerol)); + /* Positive numbers. */ + ASSERT (!signbit (ceill (0.3L))); + ASSERT (!signbit (ceill (0.7L))); + /* Negative numbers. */ + ASSERT (!!signbit (ceill (-0.3L)) == !!signbit (minus_zerol)); + ASSERT (!!signbit (ceill (-0.7L)) == !!signbit (minus_zerol)); return 0; } -- 2.11.0