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Use integer arithmetic for ND slice lengths #3240

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Use integer arithmetic for ND slice lengths #3240

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2aea92c
Use integer arithmetic for ND slice lengths
dajiaohuang Oct 2, 2026
45b14fc
Preserve unsigned slice steps above int64 range
dajiaohuang Oct 5, 2026
26e3d77
Revert "Preserve unsigned slice steps above int64 range"
dajiaohuang Oct 5, 2026
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17 changes: 16 additions & 1 deletion cpp/nd/impl/sliced_array.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@
#include <icm/slice.hpp>
#include <icm/vector.hpp>

#include <cstdint>

namespace {

template <typename I>
Expand Down Expand Up @@ -222,7 +224,20 @@ class sliced_array
if (step < 0) {
should_reverse = true;
}
dim = std::ceil((stop - start) / static_cast<float>(step));
if constexpr (std::is_integral_v<I>) {
const auto start64 = static_cast<int64_t>(start);
const auto stop64 = static_cast<int64_t>(stop);
const auto step64 = static_cast<int64_t>(step);
if (step64 > 0 && stop64 > start64) {
dim = 1 + (stop64 - start64 - 1) / step64;
} else if (step64 < 0 && stop64 < start64) {
const auto distance = static_cast<uint64_t>(start64) - static_cast<uint64_t>(stop64);
const auto step_magnitude = uint64_t{0} - static_cast<uint64_t>(step64);
dim = static_cast<int64_t>(1 + (distance - 1) / step_magnitude);
}
} else {
dim = std::ceil((stop - start) / static_cast<float>(step));
}
}

new_shape[i] = std::max(dim, static_cast<int64_t>(0));
Expand Down