version 1.1.1.1, 2000/01/10 15:35:22 |
version 1.1.1.2, 2000/09/09 14:13:08 |
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/* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop. |
/* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop. |
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Copyright (C) 1996 Free Software Foundation, Inc. |
Copyright (C) 1996, 1999 Free Software Foundation, Inc. |
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This file is part of the GNU MP Library. |
This file is part of the GNU MP Library. |
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The GNU MP Library is free software; you can redistribute it and/or modify |
The GNU MP Library is free software; you can redistribute it and/or modify |
it under the terms of the GNU Library General Public License as published by |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
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The GNU MP Library is distributed in the hope that it will be useful, but |
The GNU MP Library is distributed in the hope that it will be useful, but |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
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You should have received a copy of the GNU Library General Public License |
You should have received a copy of the GNU Lesser General Public License |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
Line 23 MA 02111-1307, USA. */ |
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Line 23 MA 02111-1307, USA. */ |
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#include "gmp-impl.h" |
#include "gmp-impl.h" |
#include "longlong.h" |
#include "longlong.h" |
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/* Algorithm: |
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1. Develop >= n bits of src.num / src.den, where n is the number of bits |
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in a double. This (partial) division will use all bits from the |
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denominator. |
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2. Use the remainder to determine how to round the result. |
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3. Assign the integral result to a temporary double. |
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4. Scale the temporary double, and return the result. |
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An alternative algorithm, that would be faster: |
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0. Let n be somewhat larger than the number of significant bits in a double. |
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1. Extract the most significant n bits of the denominator, and an equal |
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number of bits from the numerator. |
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2. Interpret the extracted numbers as integers, call them a and b |
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respectively, and develop n bits of the fractions ((a + 1) / b) and |
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(a / (b + 1)) using mpn_divrem. |
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3. If the computed values are identical UP TO THE POSITION WE CARE ABOUT, |
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we are done. If they are different, repeat the algorithm from step 1, |
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but first let n = n * 2. |
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4. If we end up using all bits from the numerator and denominator, fall |
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back to the first algorithm above. |
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5. Just to make life harder, The computation of a + 1 and b + 1 above |
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might give carry-out... Needs special handling. It might work to |
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subtract 1 in both cases instead. |
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*/ |
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void |
void |
#if __STDC__ |
#if __STDC__ |
mpf_set_q (mpf_t r, mpq_srcptr q) |
mpf_set_q (mpf_t r, mpq_srcptr q) |
Line 132 mpf_set_q (r, q) |
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Line 107 mpf_set_q (r, q) |
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} |
} |
else |
else |
{ |
{ |
nlimb = mpn_lshift (rp, np, nsize, normalization_steps); |
nlimb = mpn_lshift (rp, np, rsize, normalization_steps); |
} |
} |
if (nlimb != 0) |
if (nlimb != 0) |
{ |
{ |
rp[rsize] = nlimb; |
rp[rsize] = nlimb; |
rsize++; |
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exp++; |
exp++; |
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/* Don't just increase rsize, chop off rp at the low end instead. */ |
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if (rsize == prec) |
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rp++; |
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else |
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rsize++; |
} |
} |
} |
} |
else |
else |
Line 164 mpf_set_q (r, q) |
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Line 143 mpf_set_q (r, q) |
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} |
} |
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EXP (r) = exp; |
EXP (r) = exp; |
SIZ (r) = qsize; |
SIZ (r) = sign_quotient >= 0 ? qsize : -qsize; |
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TMP_FREE (marker); |
TMP_FREE (marker); |
} |
} |