/*

 * Copyright (c) 2003, 2007-14 Matteo Frigo

 * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology

 *

 * 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

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 *

 */

/* routines shared by the various buffered solvers */

#include "kernel/ifftw.h"

#define DEFAULT_MAXNBUF ((INT)256)

/* approx. 512KB of buffers for complex data */

#define MAXBUFSZ (256 * 1024 / (INT)(sizeof(R)))

INT X(nbuf)(INT n, INT vl, INT maxnbuf)

{

     INT i, nbuf, lb; 

     if (!maxnbuf) 

    maxnbuf = DEFAULT_MAXNBUF;

     nbuf = X(imin)(maxnbuf,

        X(imin)(vl, X(imax)((INT)1, MAXBUFSZ / n)));

     /*

      * Look for a buffer number (not too small) that divides the

      * vector length, in order that we only need one child plan:

      */

     lb = X(imax)(1, nbuf / 4);

     for (i = nbuf; i >= lb; --i)

          if (vl % i == 0)

               return i;

     /* whatever... */

     return nbuf;

}

#define SKEW 6 /* need to be even for SIMD */

#define SKEWMOD 8 

INT X(bufdist)(INT n, INT vl)

{

     if (vl == 1)

    return n;

     else 

    /* return smallest X such that X >= N and X == SKEW (mod SKEWMOD) */

    return n + X(modulo)(SKEW - n, SKEWMOD);

}

int X(toobig)(INT n)

{

     return n > MAXBUFSZ;

}

/* TRUE if there exists i < which such that maxnbuf[i] and

   maxnbuf[which] yield the same value, in which case we canonicalize

   on the minimum value */

int X(nbuf_redundant)(INT n, INT vl, size_t which, 

          const INT *maxnbuf, size_t nmaxnbuf)

{

     size_t i;

     (void)nmaxnbuf; /* UNUSED */

     for (i = 0; i < which; ++i)

    if (X(nbuf)(n, vl, maxnbuf[i]) == X(nbuf)(n, vl, maxnbuf[which]))

         return 1;

     return 0;

}