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/* Test of rounding towards negative infinity.
Copyright (C) 2007-2020 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
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2007. */
/* When this test fails on some platform, build it together with the gnulib
module 'fprintf-posix' for optimal debugging output. */
#include <config.h>
#include <math.h>
#include <float.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include "isnand-nolibm.h"
#include "macros.h"
/* MSVC with option -fp:strict refuses to compile constant initializers that
contain floating-point operations. Pacify this compiler. */
#ifdef _MSC_VER
# pragma fenv_access (off)
#endif
/* The reference implementation, taken from lib/floor.c. */
#define DOUBLE double
#define MANT_DIG DBL_MANT_DIG
#define L_(literal) literal
/* 2^(MANT_DIG-1). */
static const DOUBLE TWO_MANT_DIG =
/* Assume MANT_DIG <= 5 * 31.
Use the identity
n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
(DOUBLE) (1U << ((MANT_DIG - 1) / 5))
* (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
* (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
* (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
* (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
DOUBLE
floor_reference (DOUBLE x)
{
/* The use of 'volatile' guarantees that excess precision bits are dropped
at each addition step and before the following comparison at the caller's
site. It is necessary on x86 systems where double-floats are not IEEE
compliant by default, to avoid that the results become platform and compiler
option dependent. 'volatile' is a portable alternative to gcc's
-ffloat-store option. */
volatile DOUBLE y = x;
volatile DOUBLE z = y;
if (z > L_(0.0))
{
/* For 0 < x < 1, return +0.0 even if the current rounding mode is
FE_DOWNWARD. */
if (z < L_(1.0))
z = L_(0.0);
/* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */
else if (z < TWO_MANT_DIG)
{
/* Round to the next integer (nearest or up or down, doesn't matter). */
z += TWO_MANT_DIG;
z -= TWO_MANT_DIG;
/* Enforce rounding down. */
if (z > y)
z -= L_(1.0);
}
}
else if (z < L_(0.0))
{
/* Work around ICC's desire to optimize denormal floats to 0. */
if (z > -DBL_MIN)
return L_(-1.0);
/* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */
if (z > - TWO_MANT_DIG)
{
/* Round to the next integer (nearest or up or down, doesn't matter). */
z -= TWO_MANT_DIG;
z += TWO_MANT_DIG;
/* Enforce rounding down. */
if (z > y)
z -= L_(1.0);
}
}
return z;
}
/* Test for equality. */
static int
equal (DOUBLE x, DOUBLE y)
{
return (isnand (x) ? isnand (y) : x == y);
}
/* Test whether the result for a given argument is correct. */
static bool
correct_result_p (DOUBLE x, DOUBLE result)
{
return
(x < 0 && x >= -1 ? result == - L_(1.0) :
x - 1 < x ? result <= x && result >= x - 1 && x - result < 1 :
equal (result, x));
}
/* Test the function for a given argument. */
static int
check (double x)
{
/* If the reference implementation is incorrect, bail out immediately. */
double reference = floor_reference (x);
ASSERT (correct_result_p (x, reference));
/* If the actual implementation is wrong, return an error code. */
{
double result = floor (x);
if (correct_result_p (x, result))
return 0;
else
{
#if GNULIB_TEST_FPRINTF_POSIX
fprintf (stderr, "floor %g(%a) = %g(%a) or %g(%a)?\n",
x, x, reference, reference, result, result);
#endif
return 1;
}
}
}
#define NUM_HIGHBITS 15
#define NUM_LOWBITS 4
int
main ()
{
#ifdef UINT64_MAX
unsigned int highbits;
unsigned int lowbits;
int error = 0;
for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
{
/* Combine highbits and lowbits into a floating-point number,
sign-extending the lowbits to 64-NUM_HIGHBITS bits. */
union { double f; uint64_t i; } janus;
janus.i = ((uint64_t) highbits << (64 - NUM_HIGHBITS))
| ((uint64_t) ((int64_t) ((uint64_t) lowbits << (64 - NUM_LOWBITS))
>> (64 - NUM_LOWBITS - NUM_HIGHBITS))
>> NUM_HIGHBITS);
error |= check (janus.f);
}
return (error ? 1 : 0);
#else
fprintf (stderr, "Skipping test: no 64-bit integer type available\n");
return 77;
#endif
}
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