# std::experimental::simd_abi::fixed_size

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< cpp‎ | experimental‎ | simd

Defined in header `<experimental/simd>` |  |
template< int N > struct fixed_size {}; |  | (parallelism TS v2)

The simd_abi::fixed_size<N> tag type ensures data-parallel types to store and manipulate N elements (i.e. simd<T, simd_abi::fixed_size<N>>::size() returns N). An implementation shall support at least all N ∈ [1 … 32]. Additionally, for every supported simd<T, Abi>, where Abi is an implementation-defined ABI tag, N = simd<T, Abi>::size() shall be supported.

### Notes

An implementation may choose to forego ABI compatibility between differently compiled translation units for simd and simd_mask instantiations using the same simd_abi::fixed_size<N> tag. Otherwise, the efficiency of simd<T, Abi> is likely to be better than simd<T, fixed_size<simd_size_v<T, Abi>>> (with Abi not an instance of simd_abi::fixed_size).

### See also

max_fixed_size (parallelism TS v2) | the maximum number of elements guaranteed to be supported by fixed (constant)
scalar (parallelism TS v2) | tag type for storing a single element (typedef)
compatible (parallelism TS v2) | tag type that ensures ABI compatibility (alias template)
native (parallelism TS v2) | tag type that is most efficient (alias template)
deduce deduce_t (parallelism TS v2) | obtains an ABI type for given element type and number of elements (class template)

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