/* Round towards negative infinity.
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007, 2009, 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
#endif
/* 2^(MANT_DIG-1). */
-static const double TWO_MANT_DIG =
+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). */
volatile DOUBLE y = x;
volatile DOUBLE z = y;
- /* Round to the next integer (nearest or up or down, doesn't matter). */
if (z > L_(0.0))
{
- z += TWO_MANT_DIG;
- z -= TWO_MANT_DIG;
+ /* 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);
+ }
}
else if (z < L_(0.0))
{
- z -= TWO_MANT_DIG;
- z += TWO_MANT_DIG;
+ /* 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);
+ }
}
- /* Enforce rounding down. */
- if (z > y)
- z -= L_(1.0);
-
return z;
}