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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grow_generator_t grow_generator;
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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
{
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);
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auto point = get_crossover_point(program, c1, c2);
if (!point)
return blt::unexpected(point.error());
auto crossover_point_begin_itr = c1_ops.begin() + point->p1_crossover_point;
auto crossover_point_end_itr = c1_ops.begin() + find_endpoint(program, c1_ops, point->p1_crossover_point);
auto found_point_begin_itr = c2_ops.begin() + point->p2_crossover_point;
auto found_point_end_itr = c2_ops.begin() + find_endpoint(program, c2_ops, point->p2_crossover_point);
stack_allocator& c1_stack_init = c1.get_values();
stack_allocator& c2_stack_init = c2.get_values();
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// we have to make a copy because we will modify the underlying storage.
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std::vector<op_container_t> c1_operators;
std::vector<op_container_t> c2_operators;
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for (const auto& op : blt::iterate(crossover_point_begin_itr, crossover_point_end_itr))
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c1_operators.push_back(op);
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for (const auto& op : blt::iterate(found_point_begin_itr, found_point_end_itr))
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c2_operators.push_back(op);
stack_allocator c1_stack_after_copy;
stack_allocator c1_stack_for_copy;
stack_allocator c2_stack_after_copy;
stack_allocator c2_stack_for_copy;
// transfer all values after the crossover point. these will need to be transferred back to child2
transfer_backward(c1_stack_init, c1_stack_after_copy, c1_ops.end()-1, crossover_point_end_itr - 1);
// transfer all values for the crossover point.
transfer_backward(c1_stack_init, c1_stack_for_copy, crossover_point_end_itr - 1, crossover_point_begin_itr - 1);
// transfer child2 values for copying back into c1
transfer_backward(c2_stack_init, c2_stack_after_copy, c2_ops.end() - 1, found_point_end_itr - 1);
transfer_backward(c2_stack_init, c2_stack_for_copy, found_point_end_itr - 1, found_point_begin_itr - 1);
// now copy back into the respective children
transfer_forward(c2_stack_for_copy, c1.get_values(), found_point_begin_itr, found_point_end_itr);
transfer_forward(c1_stack_for_copy, c2.get_values(), crossover_point_begin_itr, crossover_point_end_itr);
// now copy after the crossover point back to the correct children
transfer_forward(c1_stack_after_copy, c1.get_values(), crossover_point_end_itr, c1_ops.end());
transfer_forward(c2_stack_after_copy, c2.get_values(), found_point_end_itr, c2_ops.end());
// now swap the operators
auto insert_point_c1 = crossover_point_begin_itr - 1;
auto insert_point_c2 = found_point_begin_itr - 1;
// invalidates [begin, end()) so the insert points should be fine
c1_ops.erase(crossover_point_begin_itr, crossover_point_end_itr);
c2_ops.erase(found_point_begin_itr, found_point_end_itr);
c1_ops.insert(++insert_point_c1, c2_operators.begin(), c2_operators.end());
c2_ops.insert(++insert_point_c2, c1_operators.begin(), c1_operators.end());
return result;
}
blt::expected<crossover_t::crossover_point_t, crossover_t::error_t> crossover_t::get_crossover_point(gp_program& program, const tree_t& c1,
const tree_t& c2) const
{
auto& c1_ops = c1.get_operations();
auto& c2_ops = c2.get_operations();
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blt::size_t crossover_point = program.get_random().get_size_t(1ul, c1_ops.size());
while (config.avoid_terminals && program.get_operator_info(c1_ops[crossover_point].id).argc.is_terminal())
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crossover_point = program.get_random().get_size_t(1ul, c1_ops.size());
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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)
{
bool found = false;
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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)
{
if (config.avoid_terminals && info->argc.is_terminal())
continue;
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attempted_point = i;
attempted_point_type = info;
found = true;
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break;
}
}
if (!found)
return blt::unexpected(error_t::NO_VALID_TYPE);
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}
// should we try again over the whole tree? probably not.
return blt::unexpected(error_t::NO_VALID_TYPE);
} else
{
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attempted_point = program.get_random().get_size_t(1ul, c2_ops.size());
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attempted_point_type = &program.get_operator_info(c2_ops[attempted_point].id);
if (config.avoid_terminals && attempted_point_type->argc.is_terminal())
continue;
if (crossover_point_type.return_type == attempted_point_type->return_type)
break;
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counter++;
}
} while (true);
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return crossover_point_t{static_cast<blt::ptrdiff_t>(crossover_point), static_cast<blt::ptrdiff_t>(attempted_point)};
}
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tree_t mutation_t::apply(gp_program& program, const tree_t& p)
{
auto c = p;
auto& ops = c.get_operations();
auto& vals = c.get_values();
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auto point = static_cast<blt::ptrdiff_t>(program.get_random().get_size_t(0ul, ops.size()));
const auto& type_info = program.get_operator_info(ops[point].id);
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auto begin_p = ops.begin() + point;
auto end_p = ops.begin() + find_endpoint(program, ops, point);
stack_allocator after_stack;
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for (auto it = ops.end() - 1; it != end_p - 1; it--)
{
if (it->is_value)
{
vals.transfer_bytes(after_stack, it->type_size);
//after_ops.push_back(*it);
}
}
for (auto it = end_p - 1; it != begin_p - 1; it--)
{
if (it->is_value)
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vals.pop_bytes(static_cast<blt::ptrdiff_t>(it->type_size));
}
auto before = begin_p - 1;
ops.erase(begin_p, end_p);
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auto new_tree = config.generator.get().generate({program, type_info.return_type, config.replacement_min_depth, config.replacement_max_depth});
auto& new_ops = new_tree.get_operations();
auto& new_vals = new_tree.get_values();
ops.insert(++before, new_ops.begin(), new_ops.end());
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for (auto it = new_ops.end() - 1; it != new_ops.begin() - 1; it--)
{
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if (it->is_value)
new_vals.transfer_bytes(vals, it->type_size);
}
auto new_end_point = point + new_ops.size();
auto new_end_p = ops.begin() + static_cast<blt::ptrdiff_t>(new_end_point);
for (auto it = new_end_p; it != ops.end(); it++)
{
if (it->is_value)
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after_stack.transfer_bytes(vals, it->type_size);
}
return c;
}
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mutation_t::config_t::config_t(): generator(grow_generator)
{}
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blt::ptrdiff_t find_endpoint(blt::gp::gp_program& program, const std::vector<blt::gp::op_container_t>& container, blt::ptrdiff_t index)
{
blt::i64 children_left = 0;
do
{
const auto& type = program.get_operator_info(container[index].id);
// this is a child to someone
if (children_left != 0)
children_left--;
if (type.argc.argc > 0)
children_left += type.argc.argc;
index++;
} while (children_left > 0);
return index;
}
void transfer_backward(stack_allocator& from, stack_allocator& to, detail::op_iter begin, detail::op_iter end)
{
for (auto it = begin; it != end; it--)
{
if (it->is_value)
from.transfer_bytes(to, it->type_size);
}
}
void transfer_forward(stack_allocator& from, stack_allocator& to, detail::op_iter begin, detail::op_iter end)
{
// now copy back into the respective children
for (auto it = begin; it != end; it++)
{
if (it->is_value)
from.transfer_bytes(to, it->type_size);
}
}
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}