/* Copyright (C) 2019-2021 Max-Planck-Society
   Author: Martin Reinecke */

/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-or-later */

/*
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice, this
  list of conditions and the following disclaimer in the documentation and/or
  other materials provided with the distribution.
* Neither the name of the copyright holder nor the names of its contributors may
  be used to endorse or promote products derived from this software without
  specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/*
 *  This code 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 code 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 code; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#ifndef DUCC0_MISC_UTILS_H
#define DUCC0_MISC_UTILS_H

#include <cstddef>
#include <tuple>
#ifdef __GLIBC__
#include <malloc.h>
#include <string.h>
#include <unistd.h>
#endif

namespace ducc0 {

namespace detail_misc_utils {

using namespace std;

template<typename T> auto calcShare(size_t nshares, size_t myshare,
  const T &begin, const T &end)
  {
  auto nwork = end-begin;
  auto nbase = nwork/nshares;
  auto additional = nwork%nshares;
  auto lo = begin + (myshare*nbase + ((myshare<additional) ? myshare : additional));
  auto hi = lo+nbase+(myshare<additional);
  return make_tuple(lo, hi);
  }

template<typename T> auto calcShare(size_t nshares, size_t myshare, const T &end)
  { return calcShare(nshares, myshare, T(0), end); }

template<typename shp> shp noncritical_shape(const shp &in, size_t elemsz)
  {
  constexpr size_t critstride = 4096; // must be a power of 2
  auto ndim = in.size();
  shp res(in);
  size_t stride = elemsz;
  for (size_t i=0, xi=ndim-1; i+1<ndim; ++i, --xi)
    {
    size_t tstride = stride*in[xi];
    if ((tstride&(critstride-1))==0)
       res[xi] += 3;
    stride *= res[xi];
    }
  return res;
  }

#ifdef __GLIBC__
inline bool preallocate_memory(double gbytes)
  {
  mallopt(M_MMAP_MAX, 0);  // never do mmap() for memory allocation
  mallopt(M_TRIM_THRESHOLD, -1);  // never give memory back to OS
  auto nbytes = size_t(1e9*gbytes);
  void *blob = malloc(nbytes);
  if (blob==nullptr) return false;
  memset(blob, 42, nbytes);
  // this is just to confuse the compiler sufficiently that it does not
  // eliminate all the memory operations ...
  double sum=0;
  for (size_t iblock=0; iblock<nbytes; iblock+=4096)
    sum +=((char *)blob)[iblock];
  sleep(int(sum*1e-300));
  free(blob);
  return true;
  }
#else
inline bool preallocate_memory(double /*gbytes*/)
  { return false; }
#endif

}

using detail_misc_utils::calcShare;
using detail_misc_utils::noncritical_shape;
using detail_misc_utils::preallocate_memory;

}

#endif