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slight speedup of arb_get_mag_lower, arb_get_mag_lower_nonnegative

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This commit is contained in:
Fredrik Johansson 2018-01-06 23:18:40 +01:00
parent 8ec2304863
commit 9c3b458e3c
2 changed files with 82 additions and 58 deletions
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78
arb/get_mag_lower.c
View file

@ -40,46 +40,58 @@ _arb_get_mag_lower(mag_t z, const arf_t mid, const mag_t rad)
{
mag_zero(z);
}
else if (shift <= 1) /* can be cancellation */
{
arf_t t;
arf_init(t);
arf_set_mag(t, rad);
if (arf_sgn(mid) > 0)
{
arf_sub(t, mid, t, MAG_BITS, ARF_RND_DOWN);
}
else
{
arf_add(t, mid, t, MAG_BITS, ARF_RND_DOWN);
arf_neg(t, t);
}
if (arf_sgn(t) <= 0)
mag_zero(z);
else
arf_get_mag_lower(z, t);
arf_clear(t);
}
else
{
mp_limb_t m;
mp_limb_t m, xm, rm;
ARF_GET_TOP_LIMB(m, mid);
m = m >> (FLINT_BITS - MAG_BITS);
ARF_GET_TOP_LIMB(xm, mid);
xm = xm >> (FLINT_BITS - MAG_BITS);
if (shift <= MAG_BITS)
m = m - (MAG_MAN(rad) >> shift) - 1;
rm = (MAG_MAN(rad) >> shift) + 1;
else
m = m - 1;
rm = 1;
fix = !(m >> (MAG_BITS - 1));
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
m = xm - rm;
if (shift > 1) /* more than one bit cancellation not possible */
{
fix = !(m >> (MAG_BITS - 1));
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
}
else if (rm < xm && m > (1 << (MAG_BITS - 4))) /* not too much cancellation */
{
fix = MAG_BITS - FLINT_BIT_COUNT(m);
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
}
else
{
arf_t t;
arf_init(t);
arf_set_mag(t, rad);
if (arf_sgn(mid) > 0)
{
arf_sub(t, mid, t, MAG_BITS, ARF_RND_DOWN);
}
else
{
arf_add(t, mid, t, MAG_BITS, ARF_RND_DOWN);
arf_neg(t, t);
}
if (arf_sgn(t) <= 0)
mag_zero(z);
else
arf_get_mag_lower(z, t);
arf_clear(t);
}
}
}
}

62
arb/get_mag_lower_nonnegative.c
View file

@ -44,38 +44,50 @@ _arb_get_mag_lower_nonnegative(mag_t z, const arf_t mid, const mag_t rad)
{
mag_zero(z);
}
else if (shift <= 1) /* can be cancellation */
{
arf_t t;
arf_init(t);
arf_set_mag(t, rad);
arf_sub(t, mid, t, MAG_BITS, ARF_RND_DOWN);
if (arf_sgn(t) <= 0)
mag_zero(z);
else
arf_get_mag_lower(z, t);
arf_clear(t);
}
else
{
mp_limb_t m;
mp_limb_t m, xm, rm;
ARF_GET_TOP_LIMB(m, mid);
m = m >> (FLINT_BITS - MAG_BITS);
ARF_GET_TOP_LIMB(xm, mid);
xm = xm >> (FLINT_BITS - MAG_BITS);
if (shift <= MAG_BITS)
m = m - (MAG_MAN(rad) >> shift) - 1;
rm = (MAG_MAN(rad) >> shift) + 1;
else
m = m - 1;
rm = 1;
fix = !(m >> (MAG_BITS - 1));
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
m = xm - rm;
if (shift > 1) /* more than one bit cancellation not possible */
{
fix = !(m >> (MAG_BITS - 1));
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
}
else if (rm < xm && m > (1 << (MAG_BITS - 4))) /* not too much cancellation */
{
fix = MAG_BITS - FLINT_BIT_COUNT(m);
m <<= fix;
MAG_MAN(z) = m;
_fmpz_add_fast(MAG_EXPREF(z), MAG_EXPREF(mid), -fix);
}
else
{
arf_t t;
arf_init(t);
arf_set_mag(t, rad);
arf_sub(t, mid, t, MAG_BITS, ARF_RND_DOWN);
if (arf_sgn(t) <= 0)
mag_zero(z);
else
arf_get_mag_lower(z, t);
arf_clear(t);
}
}
}
}