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Add early exit for argsort if array is already sorted #197

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Apr 15, 2025
Merged

Add early exit for argsort if array is already sorted #197

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8 changes: 7 additions & 1 deletion src/xss-common-argsort.h
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Original file line number Diff line number Diff line change
Expand Up @@ -596,7 +596,7 @@ X86_SIMD_SORT_INLINE void xss_argsort(T *arr,
bool hasnan = false,
bool descending = false)
{
/* TODO optimization: on 32-bit, use full_vector for 32-bit dtype */

using vectype = typename std::conditional<sizeof(T) == sizeof(int32_t),
half_vector<T>,
full_vector<T>>::type;
Expand All @@ -607,6 +607,7 @@ X86_SIMD_SORT_INLINE void xss_argsort(T *arr,
full_vector<arrsize_t>>::type;

if (arrsize > 1) {
/* simdargsort does not work for float/double arrays with nan */
if constexpr (xss::fp::is_floating_point_v<T>) {
if ((hasnan) && (array_has_nan<vectype>(arr, arrsize))) {
std_argsort_withnan(arr, arg, 0, arrsize);
Expand All @@ -618,6 +619,11 @@ X86_SIMD_SORT_INLINE void xss_argsort(T *arr,
}
UNUSED(hasnan);

/* early exit for already sorted arrays: float/double with nan never reach here*/
auto comp = descending ? Comparator<vectype, true>::STDSortComparator
: Comparator<vectype, false>::STDSortComparator;
if (std::is_sorted(arr, arr + arrsize, comp)) { return; }

#ifdef XSS_COMPILE_OPENMP

bool use_parallel = arrsize > 10000;
Expand Down