Transpose codec (version 1.0)#
Editor’s draft 26 July 2019
- Specification URI:
- Corresponding ZEP:
- Issue tracking:
- Suggest an edit for this spec:
Copyright 2020 Zarr core development team. This work is licensed under a Creative Commons Attribution 3.0 Unported License.
Defines a codec that permutes the dimensions of the chunk array.
Status of this document#
This document is a draft for review and subject to changes. It will become final when the Zarr Enhancement Proposal (ZEP) 1 is approved via the ZEP process.
Conformance requirements are expressed with a combination of descriptive assertions and [RFC2119] terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in [RFC2119]. However, for readability, these words do not appear in all uppercase letters in this specification.
All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. Examples in this specification are introduced with the words “for example”.
Required. Must be one of:
An array of integers specifying a permutation of
nis the number of dimensions in the decoded chunk representation provided as input to this codec.
"C", equivalent to specifying the identity permutation
n-1. This makes the codec a no-op.
"F", equivalent to specifying the permutation
Format and algorithm#
The decoded chunk representation to which this codec is applied must be an array. Implementations must fail if this codec is specified immediately after another codec that produces a byte string as its encoded representation.
Given a chunk array
A with shape
A_shape as the decoded representation,
the encoded representation is an array
B with the same data type as
B_shape[i] = A_shape[order[i]]for all dimension indices
B[B_pos] = A[A_pos], where
B_pos[i] = A_pos[order[i]], for all chunk positions
A_posand dimension indices
Implementations of this codec may simply construct a virtual view that represents the transposed result, and avoid physically transposing the in-memory representation when possible.
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://tools.ietf.org/html/rfc2119
No changes yet.