Improve the performance of get_detcost() function. #108
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gopinath-vasalamarri
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LalehB
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Aug 24, 2025
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Thanks so much, @gopinath-vasalamarri
This optimization is super cool 💯
If you get a chance, could you please also share performance results for larger numbers of shots (10K or 1M) and on other codes (surface code, color code, bivariate bicycle codes)?
| double TesseractDecoder::get_detcost( | ||
| size_t d, const std::vector<DetectorCostTuple>& detector_cost_tuples) const { | ||
| double min_cost = INF; | ||
| uint32_t min_det_cost = std::numeric_limits<uint32_t>::infinity(); |
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Does the std::numeric_limits<T>::infinity() applies for uint32_t? if it is only for floating-point types then this could become zero and later we might face division by zero issues!
| error_cost = ec.likelihood_cost / dct.detectors_count; | ||
| if (error_cost < min_cost) { | ||
| error_cost = ec.likelihood_cost; | ||
| if (error_cost < min_cost * dct.detectors_count) { |
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I like that you are replacing the div with mul 👏🏻
| error_cost = ec.likelihood_cost; | ||
| if (error_cost < min_cost * dct.detectors_count) { | ||
| min_cost = error_cost; | ||
| min_det_cost = dct.detectors_count; |
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maybe we can have a more discriptive name for this variable, something like min_cost_det_cnt?
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At the core of the change -- we are essentially swapping double_divs <-> double_muls in the for loop which, are more efficient CPU Cycle wise.
More information on comparison of before and after performance --
https://docs.google.com/spreadsheets/d/17fL_NVWe7XjwGmdBIts75YFuzUmokUyfd_YMEU9ISXY/edit?gid=0#gid=0