What is "interleaving"

Interleave \In`ter*leave"\, v. t. [imp. & p. p. Interleaved; p. pr. & vb. n. Interleaving.] [Pref. inter- + leaf.]

1. To insert a leaf or leaves in; to bind with blank leaves inserted between the others; as, to interleave a book.

2. Hence: To insert something alternately between the parts of; as, to interleave transparencies with the corresponding pages.

n. 1 The action of interleave 2 data that has undergone this action vb. (present participle of interleave English)

Interleaving may refer to:

• Interleaving, a technique for making forward error correction more robust with respect to burst errors
• An optical interleaver, a fiber-optic device to combine two sets of dense wavelength-division multiplexing (DWDM) signals
• Interleaved memory, a technique for improving the speed of access to memory
• Interleaving (disk storage), a technique for improving the speed of access to blocks on disk storage
• Interleaved posting, an e-mail posting style
• Interleaving (bitmaps), a technique for encoding bitmapped images (a specific example of data interleaving).
• Interleaving (data), the ordering of a data, either in memory or when serialised.
• Interleaving the bits of the binary representation of coordinate values to produce a Z-order (curve) for points
• Interleave sequence, a mathematical sequence formed by interleaving members of two other sequences in alternation

In disk storage and drum memory, interleaving is a technique used to improve access performance to storage by putting data accessed sequentially into non-sequential sectors.

Historically, interleaving was used in ordering block storage on disk-based storage devices such as the floppy disk and the hard disk. The primary purpose of interleaving was to adjust the timing differences between when the computer was ready to transfer data, and when that data was actually arriving at the drive head to be read. Interleaving was very common prior to the 1990s, but faded from use as processing speeds increased. Modern disk storage is not interleaved.

Interleaving was used to arrange the sectors in the most efficient manner possible, so that after reading a sector, time would be permitted for processing, and then the next sector in sequence is ready to be read just as the computer is ready to do so. Matching the sector interleave to the processing speed therefore accelerates the data transfer, but an incorrect interleave can make the system perform markedly slower.

In computing, interleaving of data refers to the interspersing of fields or channels of different meaning sequentially in memory, in processor registers, or in file formats. For example, for coordinate data, x0 y0 z0 w0 x1 y1 z1 w1 x2 y2 z2 w2 is interleaved whilst x0 x1 x2 x3 y0 y1 y2 y3 z0 z1 z2 z3 w0 w1 w2 w3 is not.

A processor may support permute instructions, or strided load and store instructions, for moving between interleaved and non interleaved representations.

Interleaving has performance implications for cache coherency, ease of leveraging SIMD hardware, and leveraging a computer's addressing modes. (e.g. - interleaved data may require one address to be calculated, from which individual fields may then be accessed via immediate offsets; conversely if only one field is required by index, de-interleaved data may leverage scaled index addressing).