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#pragma once
#include <forstio/error.hpp>
#include <forstio/codec/data.hpp>
namespace kel {
namespace lbm {
namespace sch {
using namespace saw::schema;
}
template<typename T, uint64_t D>
struct flatten_index {
public:
template<uint64_t i>
static constexpr saw::data<sch::UInt64> stride(const saw::data<sch::FixedArray<sch::UInt64,D>>& meta) {
if constexpr (i > 0u){
return stride<i-1u>(meta) * meta.at({i-1u});
}
return 1u;
}
private:
/// 2,3,4 => 2,6,24
/// i + j * 2 + k * 3*2
/// 1 + 2 * 2 + 3 * 3*2 = 1+4+18 = 23
template<uint64_t i>
static void apply_i(saw::data<sch::UInt64>& flat_ind, const saw::data<sch::FixedArray<T,D>>& index, const saw::data<sch::FixedArray<T,D>>& meta){
if constexpr ( D > i ) {
flat_ind = flat_ind + index.at({i}) * stride<i>(meta);
apply_i<i+1u>(flat_ind,index,meta);
}
}
public:
static saw::data<T> apply(const saw::data<sch::FixedArray<T,D>>& index, const saw::data<sch::FixedArray<T,D>>& meta){
saw::data<T> flat_ind{0u};
apply_i<0u>(flat_ind, index, meta);
return flat_ind;
}
};
}
}
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