blt-gp/src/transformers.cpp

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/*
* <Short Description>
* Copyright (C) 2024 Brett Terpstra
*
* 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 3 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, see <https://www.gnu.org/licenses/>.
*/
#include <blt/gp/transformers.h>
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#include <blt/gp/program.h>
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#include <blt/std/ranges.h>
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#include <random>
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namespace blt::gp
{
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blt::expected<crossover_t::result_t, crossover_t::error_t> crossover_t::apply(gp_program& program, const tree_t& p1, const tree_t& p2) // NOLINT
{
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const auto& config = program.get_config();
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result_t result{p1, p2};
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auto& c1 = result.child1;
auto& c2 = result.child2;
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auto& c1_ops = c1.get_operations();
auto& c2_ops = c2.get_operations();
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if (c1_ops.size() < 5 || c2_ops.size() < 5)
return blt::unexpected(error_t::TREE_TOO_SMALL);
std::uniform_int_distribution op_sel1(3ul, c1_ops.size() - 1);
std::uniform_int_distribution op_sel2(3ul, c2_ops.size() - 1);
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blt::size_t crossover_point = op_sel1(program.get_random());
blt::size_t attempted_point = 0;
const auto& crossover_point_type = program.get_operator_info(c1_ops[crossover_point].id);
operator_info* attempted_point_type = nullptr;
blt::size_t counter = 0;
do
{
if (counter >= config.max_crossover_tries)
{
if (config.should_crossover_try_forward)
{
for (auto i = attempted_point + 1; i < c2_ops.size(); i++)
{
auto* info = &program.get_operator_info(c2_ops[i].id);
if (info->return_type == crossover_point_type.return_type)
{
attempted_point = i;
attempted_point_type = info;
break;
}
}
}
// should we try again over the whole tree? probably not.
return blt::unexpected(error_t::NO_VALID_TYPE);
} else
{
attempted_point = op_sel2(program.get_random());
attempted_point_type = &program.get_operator_info(c2_ops[attempted_point].id);
counter++;
}
} while (crossover_point_type.return_type != attempted_point_type->return_type);
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blt::i64 children_left = 0;
blt::size_t index = crossover_point;
do
{
const auto& type = program.get_operator_info(c1_ops[index].id);
if (type.argc.argc > 0)
children_left += type.argc.argc;
else
children_left--;
index++;
} while (children_left > 0);
auto crossover_point_end_itr = c1_ops.begin() + static_cast<blt::ptrdiff_t>(index);
children_left = 0;
index = attempted_point;
do
{
const auto& type = program.get_operator_info(c2_ops[index].id);
if (type.argc.argc > 0)
children_left += type.argc.argc;
else
children_left--;
if (children_left > 0)
index++;
else
break;
} while (true);
auto found_point_end_iter = c2_ops.begin() + static_cast<blt::ptrdiff_t>(index);
stack_allocator c1_stack_init = c1.get_values();
stack_allocator c2_stack_init = c2.get_values();
std::vector<op_container_t> c1_operators;
std::vector<op_container_t> c2_operators;
for (const auto& op : blt::enumerate(c1_ops.begin() + static_cast<blt::ptrdiff_t>(crossover_point), crossover_point_end_itr))
c1_operators.push_back(op);
for (const auto& op : blt::enumerate(c2_ops.begin() + static_cast<blt::ptrdiff_t>(attempted_point), found_point_end_iter))
c2_operators.push_back(op);
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return result;
}
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}