stable_ksort.h

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/***************************************************************************
 * include/stxxl/bits/algo/stable_ksort.h
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2003 Roman Dementiev <[email protected]>
 * Copyright (C) 2008 Andreas Beckmann <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_ALGO_STABLE_KSORT_HEADER
#define STXXL_ALGO_STABLE_KSORT_HEADER

// it is a first try: distribution sort without sampling
// I rework the stable_ksort when I would have a time


#include <stxxl/bits/mng/block_manager.h>
#include <stxxl/bits/mng/buf_istream.h>
#include <stxxl/bits/mng/buf_ostream.h>
#include <stxxl/bits/common/simple_vector.h>
#include <stxxl/bits/algo/intksort.h>
#include <stxxl/bits/algo/sort_base.h>
#include <stxxl/bits/common/utils.h>


#ifndef STXXL_VERBOSE_STABLE_KSORT
#define STXXL_VERBOSE_STABLE_KSORT STXXL_VERBOSE1
#endif


STXXL_BEGIN_NAMESPACE

//! \addtogroup stlalgo
//! \{

/*! \internal
 */
namespace stable_ksort_local {

template <class type_, class type_key>
void classify_block(type_* begin, type_* end, type_key*& out, int_type* bucket, unsigned_type offset, unsigned shift)
{
 for (type_* p = begin; p < end; p++, out++) // count & create references
 {
 out->ptr = p;
 typename type_::key_type key = p->key();
 int_type ibucket = (key - offset) >> shift;
 out->key = key;
 bucket[ibucket]++;
 }
}

template <typename type>
struct type_key
{
 typedef typename type::key_type key_type;
 key_type key;
 type* ptr;

 type_key() { }
 type_key(key_type k, type* p) : key(k), ptr(p)
 { }
};

template <typename type>
bool operator < (const type_key<type>& a, const type_key<type>& b)
{
 return a.key < b.key;
}

template <typename type>
bool operator > (const type_key<type>& a, const type_key<type>& b)
{
 return a.key > b.key;
}


template <typename BIDType_, typename AllocStrategy_>
class bid_sequence
{
public:
 typedef BIDType_ bid_type;
 typedef bid_type& reference;
 typedef AllocStrategy_ alloc_strategy;
 typedef typename simple_vector<bid_type>::size_type size_type;
 typedef typename simple_vector<bid_type>::iterator iterator;

protected:
 simple_vector<bid_type>* bids;
 alloc_strategy alloc_strategy_;

public:
 bid_sequence() : bids(NULL) { }
 bid_sequence(size_type size_)
 {
 bids = new simple_vector<bid_type>(size_);
 block_manager* mng = block_manager::get_instance();
 mng->new_blocks(alloc_strategy_, bids->begin(), bids->end());
 }
 void init(size_type size_)
 {
 bids = new simple_vector<bid_type>(size_);
 block_manager* mng = block_manager::get_instance();
 mng->new_blocks(alloc_strategy_, bids->begin(), bids->end());
 }
 reference operator [] (size_type i)
 {
 size_type size_ = size(); // cache size in a register
 if (i < size_)
 return *(bids->begin() + i);

 block_manager* mng = block_manager::get_instance();
 simple_vector<bid_type>* larger_bids = new simple_vector<bid_type>((i + 1) * 2);
 std::copy(bids->begin(), bids->end(), larger_bids->begin());
 mng->new_blocks(alloc_strategy_, larger_bids->begin() + size_, larger_bids->end());
 delete bids;
 bids = larger_bids;
 return *(larger_bids->begin() + i);
 }
 size_type size() { return bids->size(); }
 iterator begin() { return bids->begin(); }
 ~bid_sequence()
 {
 block_manager::get_instance()->delete_blocks(bids->begin(), bids->end());
 delete bids;
 }
};

template <typename ExtIterator_>
void distribute(
 bid_sequence<typename ExtIterator_::vector_type::block_type::bid_type,
 typename ExtIterator_::vector_type::alloc_strategy_type>* bucket_bids,
 int64* bucket_sizes,
 const int_type nbuckets,
 const int_type lognbuckets,
 ExtIterator_ first,
 ExtIterator_ last,
 const int_type nread_buffers,
 const int_type nwrite_buffers)
{
 typedef typename ExtIterator_::vector_type::value_type value_type;
 typedef typename value_type::key_type key_type;
 typedef typename ExtIterator_::block_type block_type;
 typedef buf_istream<typename ExtIterator_::block_type,
 typename ExtIterator_::bids_container_iterator> buf_istream_type;

 int_type i = 0;

 buf_istream_type in(first.bid(), last.bid() + ((first.block_offset()) ? 1 : 0),
 nread_buffers);

 buffered_writer<block_type> out(
 nbuckets + nwrite_buffers,
 nwrite_buffers);

 unsigned_type* bucket_block_offsets = new unsigned_type[nbuckets];
 unsigned_type* bucket_iblock = new unsigned_type[nbuckets];
 block_type** bucket_blocks = new block_type*[nbuckets];

 std::fill(bucket_sizes, bucket_sizes + nbuckets, 0);
 std::fill(bucket_iblock, bucket_iblock + nbuckets, 0);
 std::fill(bucket_block_offsets, bucket_block_offsets + nbuckets, 0);

 for (i = 0; i < nbuckets; i++)
 bucket_blocks[i] = out.get_free_block();


 ExtIterator_ cur = first - first.block_offset();

 // skip part of the block before first untouched
 for ( ; cur != first; cur++)
 ++in;


 const int_type shift = sizeof(key_type) * 8 - lognbuckets;
 // search in the the range [_begin,_end)
 STXXL_VERBOSE_STABLE_KSORT("Shift by: " << shift << " bits, lognbuckets: " << lognbuckets);
 for ( ; cur != last; cur++)
 {
 key_type cur_key = in.current().key();
 int_type ibucket = cur_key >> shift;

 int_type block_offset = bucket_block_offsets[ibucket];
 in >> (bucket_blocks[ibucket]->elem[block_offset++]);
 if (block_offset == block_type::size)
 {
 block_offset = 0;
 int_type iblock = bucket_iblock[ibucket]++;
 bucket_blocks[ibucket] = out.write(bucket_blocks[ibucket], bucket_bids[ibucket][iblock]);
 }
 bucket_block_offsets[ibucket] = block_offset;
 }
 for (i = 0; i < nbuckets; i++)
 {
 if (bucket_block_offsets[i])
 {
 out.write(bucket_blocks[i], bucket_bids[i][bucket_iblock[i]]);
 }
 bucket_sizes[i] = int64(block_type::size) * bucket_iblock[i] +
 bucket_block_offsets[i];
 STXXL_VERBOSE_STABLE_KSORT("Bucket " << i << " has size " << bucket_sizes[i] <<
 ", estimated size: " << ((last - first) / int64(nbuckets)));
 }

 delete[] bucket_blocks;
 delete[] bucket_block_offsets;
 delete[] bucket_iblock;
}

} // namespace stable_ksort_local

//! Sort records with integer keys
//! \param first object of model of \c ext_random_access_iterator concept
//! \param last object of model of \c ext_random_access_iterator concept
//! \param M amount of memory for internal use (in bytes)
//! \remark Elements must provide a method key() which returns the integer key.
//! \remark Not yet fully implemented, it assumes that the keys are uniformly
//! distributed between [0,std::numeric_limits<key_type>::max().
template <typename ExtIterator_>
void stable_ksort(ExtIterator_ first, ExtIterator_ last, unsigned_type M)
{
 STXXL_MSG("Warning: stable_ksort is not yet fully implemented, it assumes that the keys are uniformly distributed between [0,std::numeric_limits<key_type>::max()]");
 typedef typename ExtIterator_::vector_type::value_type value_type;
 typedef typename value_type::key_type key_type;
 typedef typename ExtIterator_::block_type block_type;
 typedef typename block_type::bid_type bid_type;
 typedef typename ExtIterator_::vector_type::alloc_strategy_type alloc_strategy;
 typedef stable_ksort_local::bid_sequence<bid_type, alloc_strategy> bucket_bids_type;
 typedef stable_ksort_local::type_key<value_type> type_key_;

 first.flush(); // flush container

 double begin = timestamp();

 unsigned_type i = 0;
 config* cfg = config::get_instance();
 const unsigned_type m = M / block_type::raw_size;
 assert(2 * block_type::raw_size <= M);
 const unsigned_type write_buffers_multiple = 2;
 const unsigned_type read_buffers_multiple = 2;
 const unsigned_type ndisks = cfg->disks_number();
 const unsigned_type min_num_read_write_buffers = (write_buffers_multiple + read_buffers_multiple) * ndisks;
 const unsigned_type nmaxbuckets = m - min_num_read_write_buffers;
 const unsigned int lognbuckets = ilog2_floor(nmaxbuckets);
 const unsigned_type nbuckets = unsigned_type(1) << lognbuckets;
 const uint64 est_bucket_size = div_ceil((last - first) / nbuckets, block_type::size); //in blocks

 if (m < min_num_read_write_buffers + 2 || nbuckets < 2) {
 STXXL_ERRMSG("stxxl::stable_ksort: Not enough memory. Blocks available: " << m <<
 ", required for r/w buffers: " << min_num_read_write_buffers <<
 ", required for buckets: 2, nbuckets: " << nbuckets);
 throw bad_parameter("stxxl::stable_ksort(): INSUFFICIENT MEMORY provided, please increase parameter 'M'");
 }
 STXXL_VERBOSE_STABLE_KSORT("Elements to sort: " << (last - first));
 STXXL_VERBOSE_STABLE_KSORT("Number of buckets has to be reduced from " << nmaxbuckets << " to " << nbuckets);
 const unsigned_type nread_buffers = (m - nbuckets) * read_buffers_multiple / (read_buffers_multiple + write_buffers_multiple);
 const unsigned_type nwrite_buffers = (m - nbuckets) * write_buffers_multiple / (read_buffers_multiple + write_buffers_multiple);

 STXXL_VERBOSE_STABLE_KSORT("Read buffers in distribution phase: " << nread_buffers);
 STXXL_VERBOSE_STABLE_KSORT("Write buffers in distribution phase: " << nwrite_buffers);

 bucket_bids_type* bucket_bids = new bucket_bids_type[nbuckets];
 for (i = 0; i < nbuckets; ++i)
 bucket_bids[i].init(est_bucket_size);

 int64* bucket_sizes = new int64[nbuckets];

 disk_queues::get_instance()->set_priority_op(request_queue::WRITE);

 stable_ksort_local::distribute(
 bucket_bids,
 bucket_sizes,
 nbuckets,
 lognbuckets,
 first,
 last,
 nread_buffers,
 nwrite_buffers);

 double dist_end = timestamp(), end;
 double io_wait_after_d = stats::get_instance()->get_io_wait_time();

 {
 // sort buckets
 unsigned_type write_buffers_multiple_bs = 2;
 unsigned_type max_bucket_size_bl = (m - write_buffers_multiple_bs * ndisks) / 2; // in number of blocks
 int64 max_bucket_size_rec = int64(max_bucket_size_bl) * block_type::size; // in number of records
 int64 max_bucket_size_act = 0; // actual max bucket size
 // establish output stream

 for (i = 0; i < nbuckets; i++)
 {
 max_bucket_size_act = STXXL_MAX(bucket_sizes[i], max_bucket_size_act);
 if (bucket_sizes[i] > max_bucket_size_rec)
 {
 STXXL_ERRMSG("Bucket " << i << " is too large: " << bucket_sizes[i] <<
 " records, maximum: " << max_bucket_size_rec);
 STXXL_ERRMSG("Recursion on buckets is not yet implemented, aborting.");
 abort();
 }
 }
 // here we can increase write_buffers_multiple_b knowing max(bucket_sizes[i])
 // ... and decrease max_bucket_size_bl
 const int_type max_bucket_size_act_bl = div_ceil(max_bucket_size_act, block_type::size);
 STXXL_VERBOSE_STABLE_KSORT("Reducing required number of required blocks per bucket from " <<
 max_bucket_size_bl << " to " << max_bucket_size_act_bl);
 max_bucket_size_rec = max_bucket_size_act;
 max_bucket_size_bl = max_bucket_size_act_bl;
 const unsigned_type nwrite_buffers_bs = m - 2 * max_bucket_size_bl;
 STXXL_VERBOSE_STABLE_KSORT("Write buffers in bucket sorting phase: " << nwrite_buffers_bs);

 typedef buf_ostream<block_type, typename ExtIterator_::bids_container_iterator> buf_ostream_type;
 buf_ostream_type out(first.bid(), nwrite_buffers_bs);

 disk_queues::get_instance()->set_priority_op(request_queue::READ);

 if (first.block_offset())
 {
 // has to skip part of the first block
 block_type* block = new block_type;
 request_ptr req;
 req = block->read(*first.bid());
 req->wait();

 for (i = 0; i < first.block_offset(); i++)
 {
 out << block->elem[i];
 }
 delete block;
 }
 block_type* blocks1 = new block_type[max_bucket_size_bl];
 block_type* blocks2 = new block_type[max_bucket_size_bl];
 request_ptr* reqs1 = new request_ptr[max_bucket_size_bl];
 request_ptr* reqs2 = new request_ptr[max_bucket_size_bl];
 type_key_* refs1 = new type_key_[max_bucket_size_rec];
 type_key_* refs2 = new type_key_[max_bucket_size_rec];

 // submit reading first 2 buckets (Peter's scheme)
 unsigned_type nbucket_blocks = div_ceil(bucket_sizes[0], block_type::size);
 for (i = 0; i < nbucket_blocks; i++)
 reqs1[i] = blocks1[i].read(bucket_bids[0][i]);


 nbucket_blocks = div_ceil(bucket_sizes[1], block_type::size);
 for (i = 0; i < nbucket_blocks; i++)
 reqs2[i] = blocks2[i].read(bucket_bids[1][i]);


 key_type offset = 0;
 const unsigned log_k1 = STXXL_MAX<unsigned>(ilog2_ceil(max_bucket_size_rec * sizeof(type_key_) / STXXL_L2_SIZE), 1);
 unsigned_type k1 = unsigned_type(1) << log_k1;
 int_type* bucket1 = new int_type[k1];

 const unsigned int shift = (unsigned int)(sizeof(key_type) * 8 - lognbuckets);
 const unsigned int shift1 = shift - log_k1;

 STXXL_VERBOSE_STABLE_KSORT("Classifying " << nbuckets << " buckets, max size:" << max_bucket_size_rec <<
 " block size:" << block_type::size << " log_k1:" << log_k1);

 for (unsigned_type k = 0; k < nbuckets; k++)
 {
 nbucket_blocks = div_ceil(bucket_sizes[k], block_type::size);
 const unsigned log_k1_k = STXXL_MAX<unsigned>(ilog2_ceil(bucket_sizes[k] * sizeof(type_key_) / STXXL_L2_SIZE), 1);
 assert(log_k1_k <= log_k1);
 k1 = (unsigned_type)(1) << log_k1_k;
 std::fill(bucket1, bucket1 + k1, 0);

 STXXL_VERBOSE_STABLE_KSORT("Classifying bucket " << k << " size:" << bucket_sizes[k] <<
 " blocks:" << nbucket_blocks << " log_k1:" << log_k1_k);
 // classify first nbucket_blocks-1 blocks, they are full
 type_key_* ref_ptr = refs1;
 key_type offset1 = offset + (key_type(1) << key_type(shift)) * key_type(k);
 for (i = 0; i < nbucket_blocks - 1; i++)
 {
 reqs1[i]->wait();
 stable_ksort_local::classify_block(blocks1[i].begin(), blocks1[i].end(), ref_ptr, bucket1, offset1, shift1 /*,k1*/);
 }
 // last block might be non-full
 const unsigned_type last_block_size = bucket_sizes[k] - int64(nbucket_blocks - 1) * block_type::size;
 reqs1[i]->wait();

 //STXXL_MSG("block_type::size: "<<block_type::size<<" last_block_size:"<<last_block_size);

 classify_block(blocks1[i].begin(), blocks1[i].begin() + last_block_size, ref_ptr, bucket1, offset1, shift1);

 exclusive_prefix_sum(bucket1, k1);
 classify(refs1, refs1 + bucket_sizes[k], refs2, bucket1, offset1, shift1);

 type_key_* c = refs2;
 type_key_* d = refs1;
 for (i = 0; i < k1; i++)
 {
 type_key_* cEnd = refs2 + bucket1[i];
 type_key_* dEnd = refs1 + bucket1[i];

 const unsigned log_k2 = ilog2_floor(bucket1[i]) - 1; // adaptive bucket size
 const unsigned_type k2 = unsigned_type(1) << log_k2;
 int_type* bucket2 = new int_type[k2];
 const unsigned shift2 = shift1 - log_k2;

 // STXXL_MSG("Sorting bucket "<<k<<":"<<i);
 l1sort(c, cEnd, d, bucket2, k2,
 offset1 + (key_type(1) << key_type(shift1)) * key_type(i),
 shift2);

 // write out all
 for (type_key_* p = d; p < dEnd; p++)
 out << (*(p->ptr));


 delete[] bucket2;
 c = cEnd;
 d = dEnd;
 }
 // submit next read
 const unsigned_type bucket2submit = k + 2;
 if (bucket2submit < nbuckets)
 {
 nbucket_blocks = div_ceil(bucket_sizes[bucket2submit], block_type::size);
 for (i = 0; i < nbucket_blocks; i++)
 reqs1[i] = blocks1[i].read(bucket_bids[bucket2submit][i]);
 }

 std::swap(blocks1, blocks2);
 std::swap(reqs1, reqs2);
 }

 delete[] bucket1;
 delete[] refs1;
 delete[] refs2;
 delete[] blocks1;
 delete[] blocks2;
 delete[] reqs1;
 delete[] reqs2;
 delete[] bucket_bids;
 delete[] bucket_sizes;

 if (last.block_offset())
 {
 // has to skip part of the first block
 block_type* block = new block_type;
 request_ptr req = block->read(*last.bid());
 req->wait();

 for (i = last.block_offset(); i < block_type::size; i++)
 {
 out << block->elem[i];
 }
 delete block;
 }

 end = timestamp();
 }

 STXXL_VERBOSE("Elapsed time : " << end - begin << " s. Distribution time: " <<
 dist_end - begin << " s");
 STXXL_VERBOSE("Time in I/O wait(ds): " << io_wait_after_d << " s");
 STXXL_VERBOSE(*stats::get_instance());
 STXXL_UNUSED(begin + dist_end + end + io_wait_after_d);
}

//! \}

STXXL_END_NAMESPACE

#endif // !STXXL_ALGO_STABLE_KSORT_HEADER