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Initial commit: cuGenOpt GPU optimization solver

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L-yang-yang 2026-03-20 00:33:45 +08:00
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71
python/cugenopt/operator_packs/knapsack.py Normal file
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"""
Knapsack-specific custom operators.
These operators exploit knapsack structure (value/weight ratio awareness)
to make more informed bit-flip decisions.
"""
from cugenopt.operators import CustomOperator
_KNAPSACK_GREEDY_FLIP = CustomOperator(
name="knapsack_greedy_flip",
code=r"""
int row = 0;
int sz = sol.dim2_sizes[row];
if (sz < 2) return false;
const float* weights = prob->d_weights;
const float* values = prob->d_values;
int pos = rand_int(rng, sz);
if (sol.data[row][pos] == 0) {
float ratio = (weights[pos] > 0.001f)
? values[pos] / weights[pos] : 0.0f;
if (ratio > 0.5f || curand_uniform(rng) < 0.3f) {
sol.data[row][pos] = 1;
return true;
}
} else {
float ratio = (weights[pos] > 0.001f)
? values[pos] / weights[pos] : 1e6f;
if (ratio < 0.5f || curand_uniform(rng) < 0.3f) {
sol.data[row][pos] = 0;
return true;
}
}
return false;
""",
encoding="binary",
initial_weight=0.8,
)
_KNAPSACK_SWAP_RATIO = CustomOperator(
name="knapsack_swap_ratio",
code=r"""
int row = 0;
int sz = sol.dim2_sizes[row];
if (sz < 2) return false;
const float* weights = prob->d_weights;
const float* values = prob->d_values;
int in_item = -1, out_item = -1;
for (int t = 0; t < 8; t++) {
int p = rand_int(rng, sz);
if (sol.data[row][p] == 1 && in_item < 0) in_item = p;
if (sol.data[row][p] == 0 && out_item < 0) out_item = p;
if (in_item >= 0 && out_item >= 0) break;
}
if (in_item < 0 || out_item < 0) return false;
float in_ratio = (weights[in_item] > 0.001f)
? values[in_item] / weights[in_item] : 1e6f;
float out_ratio = (weights[out_item] > 0.001f)
? values[out_item] / weights[out_item] : 0.0f;
if (out_ratio > in_ratio || curand_uniform(rng) < 0.2f) {
sol.data[row][in_item] = 0;
sol.data[row][out_item] = 1;
return true;
}
return false;
""",
encoding="binary",
initial_weight=0.8,
)
knapsack_ops = [_KNAPSACK_GREEDY_FLIP, _KNAPSACK_SWAP_RATIO]