diff options
Diffstat (limited to 'src/math/__rem_pio2.c')
| -rw-r--r-- | src/math/__rem_pio2.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/src/math/__rem_pio2.c b/src/math/__rem_pio2.c index d403f81c..dcf672fb 100644 --- a/src/math/__rem_pio2.c +++ b/src/math/__rem_pio2.c @@ -36,6 +36,7 @@ */ static const double toint = 1.5/EPS, +pio4 = 0x1.921fb54442d18p-1, invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */ pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */ pio2_1t = 6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */ @@ -117,11 +118,23 @@ int __rem_pio2(double x, double *y) } if (ix < 0x413921fb) { /* |x| ~< 2^20*(pi/2), medium size */ medium: - /* rint(x/(pi/2)), Assume round-to-nearest. */ + /* rint(x/(pi/2)) */ fn = (double_t)x*invpio2 + toint - toint; n = (int32_t)fn; r = x - fn*pio2_1; w = fn*pio2_1t; /* 1st round, good to 85 bits */ + /* Matters with directed rounding. */ + if (predict_false(r - w < -pio4)) { + n--; + fn--; + r = x - fn*pio2_1; + w = fn*pio2_1t; + } else if (predict_false(r - w > pio4)) { + n++; + fn++; + r = x - fn*pio2_1; + w = fn*pio2_1t; + } y[0] = r - w; u.f = y[0]; ey = u.i>>52 & 0x7ff; |