1. Introduction to Bifrost¶

1.2.1. Streaming data¶

The purpose of bifrost is to allow rapid development of streaming DSP pipelines; that is, it is designed for stream-like data. A simple example of a data stream is the time series voltage data from a radio telescope’s digitizer card. Unlike file-like data, stream-like data has no well defined start and stop points. One can of course take a series of files, each containing a chunk of a time stream, and treat them as a stream.

1.2.2. Pipelines¶

A pipeline is a programming implementation where data processing elements are daisy-chained together and stream data are pushed through them – like water through a pipe. The data processing elements all run at once, each processing different bits of data which “flow” through the pipeline.

Pipelining can significantly improve a code’s performance (image a road system with only one car on it at one time: that would be an ‘unpipelined’ transport system!). Nevertheless, if there is a particularly slow processing element, the flow of the pipeline will be limited by that element’s output data rate– this is known as a bottleneck.

1.2.3. Ring buffers¶

A common way to implement pipelines is to connect data processing elements together with buffer memory storage. Bifrost uses this approach, and the specific implementation is known as a ring buffer, or just ring. The ring is shared between processing elements: one element writes to the ring, while the other processing element reads from the ring.

1.2.4. Blocks¶

In Bifrost, anything that does something to a data stream is called a block. Conceptually, there are three kinds of blocks: * tasks: A block that reads from a ring, transforms the data in some way, and writes it out to an output ring. * source: A block that generates data, or loads it from outside the pipeline (e.g. a file or an Ethernet stream), and writes it to an output ring. * sink: A block that reads data from an input ring and plots it, or writes it to file, or generally does something without any pipeline output.

A simple pipeline would be a source block (e.g. file read), connected to a task block (compute average), connected to a sink block (plot time series of moving averaged data).