Developer Guide and Reference

  • 2021.6
  • 04/11/2022
  • Public Content

Types of Numeric Tables

Heterogeneous Numeric Tables

Heterogeneous numeric tables enable you to deal with data structures that are of different data types by nature. oneDAL provides two ways to represent non-homogeneous numeric tables: AOS and SOA.
AOS Numeric Table
AOS Numeric Table provides access to observations (feature vectors) that are laid out in a contiguous memory block:
Array-Of-Structures (AOS) Memory Layout
SOA Numeric Table
SOA Numeric Table provides access to data sets where observations for each feature are laid out contiguously in memory:
Structure-Of-Arrays (SOA) Memory Layout

Homogeneous Numeric Tables

Use homogeneous numeric tables, that is, objects of the
class, and matrices, that is, objects of the
, and
classes, when all the features are of the same basic data type. Values of the features are laid out in memory as one contiguous block in the row-major order, that is,
Observation 1
Observation 2
, and so on. In oneDAL,
is a homogeneous numeric table most suitable for matrix algebra operations.
For triangular and symmetric matrices with reduced memory footprint, special classes are available:
. Use the DataLayout enumeration to choose between representations of triangular and symmetric matrices:
  • Lower packed:
  • Upper packed:
Packed Storage Format for Symmetric and Triangular Matrices

CSR Numeric Table

oneDAL offers the
class for a special version of a homogeneous numeric table that encodes sparse data, that is, the data with a significant number of zero elements. The library uses the Condensed Sparse Row (CSR) format for encoding:
Condensed Sparse Row (CSR) 0-Based Encoding
Condensed Sparse Row (CSR) 1-Based Encoding
Three arrays describe the sparse matrix M as follows:
  • The array values contains non-zero elements of the matrix row-by-row.
  • The j-th element of the array columns encodes the column index in the matrix M for the j-th element of the array values.
  • The i-th element of the array rowIndex encodes the index in the array values corresponding to the first non-zero element in rows indexed i or greater. The last element in the array rowIndex encodes the number of non-zero elements in the matrix M.
The library supports 1-based CSR encoding only. In C++ you can specify it by providingoneBased value through the indexing parameter of type
in the constructor of

Merged Numeric Table

oneDAL offers the
class for tables that provides access to data sets comprising several logical components, such as a set of feature vectors and corresponding labels. This type of tables enables you to read those data components from one data source. This special type of numeric tables can hold several numeric tables of any type but
. In a merged numeric table, arrays are joined by columns and therefore can have different numbers of columns. In the case of different numbers of rows in input matrices, the number of rows in a merged table equals LaTex Math image., where LaTex Math image. is the number of rows in the i-th matrix, LaTex Math image..
Merged Numeric Table

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