scanWGSL¶

Overview¶

A template that performs a scan operation using workgroup memory on a single workgroup (one value per thread).

@author Jonathan Olson <jonathan.olson@colorado.edu>

Type scanWGSLOptions¶

import type { scanWGSLOptions } from 'scenerystack/alpenglow';

• value: WGSLVariableName
  the "input" and "output" variable name
• scratch: WGSLVariableName
  name for var<workgroup> array<T, workgroupSize> TODO: consider abstracting, so we could run multiple reduces TODO: concurrently
• direction?: "left" | "right"
  The direction of the scan. For instance, a left inclusive scan of [ 1, 2, 3, 4 ] is [ 1, 3, 6, 10 ], but a right incluive scan is [ 10, 9, 7, 4 ] (just scans in the other direction)
• binaryOp: BinaryOp<T>
• mapScratchIndex?: ( index: WGSLExpressionU32 ) => WGSLExpressionU32
  allows overriding the index used for the scratch array, so that we can run multiple smaller loads in the same workgroup
• exclusive?: boolean
  boolean (whether the scan should be exclusive - otherwise it is inclusive). e.g. an inclusive left scan of [ 1, 2, 3, 4 ] is [ 1, 3, 6, 10 ], whereas an exclusive left scan is [ 0, 1, 3, 6 ]
• needsValidScratch?: boolean
  if the scratch value doesn't need to be accurate, we can skip this
• scratchPreloaded?: boolean
  TODO: some of this is duplicated with reduce.wgsl, how can we factor it out? If true, we won't need to load the value INTO the scratch array
• valuePreloaded?: boolean
  If true, we won't need to load the value FROM the scratch array
• & WorkgroupSizable & LocalIndexable

Source Code¶

See the source for scanWGSL.ts in the alpenglow repository.