multi_bit_sel_bloom_filter.cc

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/*
 * Copyright (c) 2019 Inria
 * Copyright (c) 1999-2008 Mark D. Hill and David A. Wood
 * 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 holders 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
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#include "base/filters/multi_bit_sel_bloom_filter.hh"
 
#include <limits>
 
#include "base/bitfield.hh"
#include "base/logging.hh"
#include "params/BloomFilterMultiBitSel.hh"
 
namespace gem5
{
 
namespace bloom_filter
{
 
MultiBitSel::MultiBitSel(const BloomFilterMultiBitSelParams &p)
    : Base(p), numHashes(p.num_hashes),
      parFilterSize(p.size / numHashes),
      isParallel(p.is_parallel), skipBits(p.skip_bits)
{
    if (p.size % numHashes) {
        fatal("Can't divide filter (%d) in %d equal portions", p.size,
              numHashes);
    }
}
 
MultiBitSel::~MultiBitSel()
{
}
 
void
MultiBitSel::set(Addr addr)
{
    for (int i = 0; i < numHashes; i++) {
        filter[hash(addr, i)]++;
    }
}
 
int
MultiBitSel::getCount(Addr addr) const
{
    int count = 0;
    for (int i=0; i < numHashes; i++) {
        count += filter[hash(addr, i)];
    }
    return count;
}
 
int
MultiBitSel::hash(Addr addr, int hash_number) const
{
    uint64_t value = bits(addr, std::numeric_limits<Addr>::digits - 1,
        offsetBits) >> skipBits;
    const int max_bits = std::numeric_limits<Addr>::digits - offsetBits;
    int result = 0;
    int bit, i;
 
    for (i = 0; i < sizeBits; i++) {
        bit = (hash_number + numHashes * i) % max_bits;
        if (value & (1 << bit)) {
            result += 1 << i;
        }
    }
 
    if (isParallel) {
        return (result % parFilterSize) + hash_number * parFilterSize;
    } else {
        return result % filter.size();
    }
}
 
} // namespace bloom_filter
} // namespace gem5