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README > Terminology

CUTLASS Terminology

AlignedBuffer<T, N>: statically sized array type; union-safe, no construction guarantee for elements

Array<T, N>: container for holding numeric types - handles bit packing for small numeric types (e.g. int4_t, uint4_t, bin1_t) sizeof(Array<T, N>) - gives expected value in units of bytes with minimum storage of 1 B: (sizeof_bits::value * N) / 8

Capacity: (scalar) physical number of elements in memory required to store a multidimensional object; expressed as the type's LongIndex type

  • example: the capacity of a column-major matrix is lda * N

Element: data type describing one item in a multidimensional tensor, array, or matrix

Extent: (vector-valued quantity) the logical size of each dimension of a multidimensional index space. Consistent with the C++ Standard Library.

  • Coord<N> extent()
  • Index extent(int dim)

Fragment: a register-backed array of elements used to store a thread's part of a tile

Index: signed integer representing quantities aligned with a logical dimension

Layout: functor mapping logical coordinates of a tensor to linear offset (as LongIndex); owns stride vectors, if any.

LongIndex: signed integer representing offsets in memory; typically wider than Index type

Numeric Type: a CUTLASS data type used to represent real-valued quantities; is trivially copyable.

Operator: an object performing a computation on matrix or tensor objects. May be further refined by scope within the execution model hierarchy.

Pitch Linear: linear memory allocation obtained from a user-defined 2-D size, which specifies the contiguous and strided dimensions of a tile.

Planar Complex: representation of complex tensors as two real-valued tensors, with real elements in one part and imaginary elements in another part of identical layout, separated by an offset

Policy: additional details extending the interface of a template guiding internal implementation; typically used to target specific design points known to be efficient

Rank: number of dimensions in a multidimensional index space, array, tensor, or matrix. Consistent with C++ Standard Library

Register: in device code, registers are the most efficient storage for statically sized arrays of elements. Arrays may be expected to be stored in registers if all accesses are made via constexpr indices or within fully unrolled loops.

Residue: partial tile or matrix computation which may require special accommodation for functional correctness or performance

Size: (scalar) number of logical elements in a tensor; equal to the product of each member of extent()

  • LongIndex size()

sizeof_bits<T>::value - template pattern returning the size of a numeric type or array in units of bits

Storage: when appropriate, refers to some alternative type used to store a packed collection of elements; may be used to handle bit-level packing or make types safe for use in unions

TensorRef: contains base pointer and Layout object for referencing infinitely-sized tensor object

TensorView: contains TensorRef and extent of a finite mathematical object

Tile: partitions of a tensor that have constant extents and layout known at compile time

Tile Iterator: abstraction for accessing and traversing a sequence of tiles in a tensor; CUTLASS specifies formal concepts for tile iterators

Thread Map: abstraction for defining how threads are mapped to a given tile.

Trait: characteristics of a fully-specialized type, typically used in metaprogramming reflection

View: an object containing references to a data structure that it does not own; typically, construction of views is lightweight

Warp: a collection of hardware threads executing in lock-step; warp-level operations typically rely on cooperation among the threads within the warp

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