BitMagicC++Library
sample12.cpp

Example of how to use various bit setting techniques.Several techniques benchmarked to better illustrate relative performance.

See also
bm::bvector<>::set()
bm::bvector<>::set_bit()
bm::bvector<>::set_bit_conditional()
bm::bvector<>::set_range()
bm::bvector<>::clear_bit()
bm::bvector<>::reset()
bm::bvector<>::flip()
bm::bvector<>::swap()
bm::bvector<>::extract_next()
bm::bvector<>::set_bit_no_check()
bm::combine_or()
/*
Copyright(c) 2002-2017 Anatoliy Kuznetsov(anatoliy_kuznetsov at yahoo.com)
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
For more information please visit: http://bitmagic.io
*/
/** \example sample12.cpp
Example of how to use various bit setting techniques.
Several techniques benchmarked to better illustrate relative performance.
\sa bm::bvector<>::set()
\sa bm::bvector<>::set_bit()
\sa bm::bvector<>::set_bit_conditional()
\sa bm::bvector<>::set_range()
\sa bm::bvector<>::clear_bit()
\sa bm::bvector<>::reset()
\sa bm::bvector<>::flip()
\sa bm::bvector<>::swap()
\sa bm::bvector<>::extract_next()
\sa bm::bvector<>::set_bit_no_check()
\sa bm::combine_or()
*/
#include <iostream>
#include <vector>
#include "bm.h"
#include "bmalgo.h"
#include "bmtimer.h"
using namespace std;
// timing storage for benchmarking
bm::chrono_taker::duration_map_type timing_map;
const unsigned benchmark_count = 1000;
unsigned vector_max = 4000000;
// Utility template function used to print container
template<class T> void PrintContainer(T first, T last)
{
if (first == last)
std::cout << "<EMPTY SET>";
else
for (; first != last; ++first)
std::cout << *first << ";";
std::cout << endl;
}
void generate_test_vectors(std::vector<bm::id_t> &v1,
std::vector<bm::id_t> &v2,
std::vector<bm::id_t> &v3)
{
for (j = 0; j < vector_max; j += 2)
{
v1.push_back(j);
}
for (j = 0; j < vector_max; j += 10)
{
v2.push_back(j);
}
for (j = 0; j < vector_max; j += 120)
{
v3.push_back(j);
}
}
// stress test for bm::bvector<>::set_bit()
//
{
bm::chrono_taker tt1("1. bvector<>::set_bit()", benchmark_count, &timing_map);
bm::bvector<> bv1, bv2, bv3;
for (unsigned i = 0; i < benchmark_count; ++i)
{
for (j = 0; j < vector_max; j += 2)
{
bv1.set_bit(j, true);
}
for (j = 0; j < vector_max; j += 10)
{
bv2.set_bit(j, true);
}
for (j = 0; j < vector_max; j += 120)
{
bv3.set_bit(j, true);
}
bv1.reset();
bv2.reset();
bv3.reset();
} // for
}
// stress test for bm::bvector<>::set_bit()
//
{
bm::chrono_taker tt1("2. bvector<>::set_bit_no_check()", benchmark_count, &timing_map);
bm::bvector<> bv1, bv2, bv3;
bv1.init();
bv2.init();
bv3.init();
for (unsigned i = 0; i < benchmark_count; ++i)
{
for (j = 0; j < vector_max; j += 2)
{
}
for (j = 0; j < vector_max; j += 10)
{
}
for (j = 0; j < vector_max; j += 120)
{
}
}
}
void combine_or_test(std::vector<bm::id_t> &v1,
std::vector<bm::id_t> &v2,
std::vector<bm::id_t> &v3)
{
bm::chrono_taker tt1("3. combine_or()", benchmark_count, &timing_map);
bm::bvector<> bv1, bv2, bv3;
for (unsigned i = 0; i < benchmark_count; ++i)
{
bm::combine_or(bv1, v1.begin(), v1.end());
bm::combine_or(bv2, v2.begin(), v2.end());
bm::combine_or(bv3, v3.begin(), v3.end());
}
}
int main(void)
{
try
{
// 0. create bvector, use brace initialization to add some initial data
//
bm::bvector<> bv1 { 2, 3, 4 };
PrintContainer(bv1.first(), bv1.end()); // 2, 3, 4
bv1.clear();
// 1. Set some bits using regular bvector<>::set() method
//
bv1.set(10);
bv1.set(256);
bv1.set(1000000);
PrintContainer(bv1.first(), bv1.end()); // 10, 256, 1000000
// 2. now use bvector<>::set_bit()
// it returns a report if target actually changed
//
bm::id_t bits[] = { 256, 512, 10 };
unsigned cnt = 0;
for (unsigned i = 0; i < sizeof(bits) / sizeof(bits[0]); ++i)
{
bool b = bv1.set_bit(bits[i], true);
cnt += b;
}
std::cout << "Number of bits changed:" << cnt << std::endl;
PrintContainer(bv1.first(), bv1.end());
// 3. set and clear some bits using bvector<>::set_bit_conditional()
// method sets bit n only if current value equals the condition
//
bool b;
b = bv1.set_bit_conditional(5, true, false); // set bit 5 to true if it is false (yes)
std::cout << "Bit 5 set:" << (b ? " yes " : " no ") << std::endl; // (yes)
b = bv1.set_bit_conditional(256, true, false); // set bit 256 to true if it is false
std::cout << "Bit 256 set:" << (b ? " yes " : " no ") << std::endl; // (no)
b = bv1.set_bit_conditional(256, true, true); // set bit 256 to true if it is true
std::cout << "Bit 256 set:" << (b ? " yes " : " no ") << std::endl; // (no)
PrintContainer(bv1.first(), bv1.end());
// 4. set or clear multiple bits using bvector::set_range()
// This method is faster than calling bvector::set() many times in a row
//
bv1.set_range(10, 15, true); // set all bits in [10..15] closed interval
PrintContainer(bv1.first(), bv1.end());
bv1.set_range(10, 12, false); // clear all bits in [10..15] closed interval
PrintContainer(bv1.first(), bv1.end());
// 5. bvector::clear_bit() - same as set_bit() just a syntax sugar
//
b = bv1.clear_bit(13);
std::cout << "Bit 13 set:" << (b ? " yes " : " no ") << std::endl; // (yes)
// 6. bvector<>::reset() - clears all the bits, frees the blocks memory
// same as bvector<>::clear(true);
//
bv1.reset();
PrintContainer(bv1.first(), bv1.end()); // <EMPTY>
// 7. use bm::combine_or() to set bits
//
bm::combine_or(bv1, &bits[0], &bits[0] + (sizeof(bits) / sizeof(bits[0])));
PrintContainer(bv1.first(), bv1.end()); // 10, 256, 512
// 8. use bvector<>::flip( ) to flip a bit
//
bv1.flip(256);
bv1.flip(257);
PrintContainer(bv1.first(), bv1.end()); // 10, 257, 512
// 9. bvector<>::swap() to flip content of two bit-vectors
//
bv1.swap(bv2);
PrintContainer(bv1.first(), bv1.end()); // <EMPTY>
PrintContainer(bv2.first(), bv2.end()); // 10, 257, 512
// 10. use bvector<>::extract_next() to find ON bit and turn it to 0
// this function is useful for building FIFO queues on bvector
//
bm::id_t p = 1;
for (p = bv2.extract_next(p); p != 0; p = bv2.extract_next(p))
{
std::cout << "Extracted p = " << p << std::endl;
}
PrintContainer(bv2.first(), bv2.end()); // <EMPTY>
// 11. use bvector<>::set_bit_no_check() to set bits faster
//
bv3.init(); // the key here you MUST call init() before setting bits this way
bv3.set_bit_no_check(10);
bv3.set_bit_no_check(100);
bv3.set_bit_no_check(1000);
PrintContainer(bv3.first(), bv3.end()); // 10, 100, 1000
std::vector<bm::id_t> v1, v2, v3;
generate_test_vectors(v1, v2, v3);
for (unsigned k = 0; k < 1000; ++k)
{
// run a few CPU "pre-heat" loops to get consistent results
unsigned s = 0;
unsigned i;
for (i = 0; i < v1.size(); ++i)
s = s + s* v1[i] + i;
for (i = 0; i < v2.size(); ++i)
s = s + s* v2[i] + i;
std::cout << s << "\r";
}
std::cout << std::endl << "Running benchmarks..." << std::endl;
combine_or_test(v1, v2, v3);
// print all test timing results
//
std::cout << std::endl;
bm::chrono_taker::print_duration_map(timing_map, bm::chrono_taker::ct_ops_per_sec);
}
catch(std::exception& ex)
{
std::cerr << ex.what() << std::endl;
return 1;
}
return 0;
}