Blame mpz/sqrt.c

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/* mpz_sqrt(root, u) --  Set ROOT to floor(sqrt(U)).
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Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2005, 2012 Free Software
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Foundation, Inc.
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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
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it under the terms of either:
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  * the GNU Lesser General Public License as published by the Free
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    Software Foundation; either version 3 of the License, or (at your
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    option) any later version.
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or
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  * the GNU General Public License as published by the Free Software
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    Foundation; either version 2 of the License, or (at your option) any
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    later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library.  If not,
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see https://www.gnu.org/licenses/.  */
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#include <stdio.h> /* for NULL */
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#include "gmp.h"
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#include "gmp-impl.h"
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void
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mpz_sqrt (mpz_ptr root, mpz_srcptr op)
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{
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  mp_size_t op_size, root_size;
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  mp_ptr root_ptr, op_ptr;
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  op_size = SIZ (op);
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  if (UNLIKELY (op_size <= 0))
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    {
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      if (op_size < 0)
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	SQRT_OF_NEGATIVE;
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      SIZ(root) = 0;
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      return;
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    }
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  /* The size of the root is accurate after this simple calculation.  */
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  root_size = (op_size + 1) / 2;
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  SIZ (root) = root_size;
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  op_ptr = PTR (op);
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  if (root == op)
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    {
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      /* Allocate temp space for the root, which we then copy to the
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	 shared OP/ROOT variable.  */
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      TMP_DECL;
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      TMP_MARK;
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      root_ptr = TMP_ALLOC_LIMBS (root_size);
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      mpn_sqrtrem (root_ptr, NULL, op_ptr, op_size);
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      MPN_COPY (op_ptr, root_ptr, root_size);
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      TMP_FREE;
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    }
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  else
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    {
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      root_ptr = MPZ_NEWALLOC (root, root_size);
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      mpn_sqrtrem (root_ptr, NULL, op_ptr, op_size);
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    }
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}