Class: PrefixScan<T>
A cascade of shaders to do a prefix scan operation, based on a shader that does a prefix scan of a workgroup sized chunk of data (e.g. 64 or 256 elements).
The scan operation is parameterized by the module mechanism. The user can instantiate a PrefixScan with sum to get prefix-sum, or use another module for other parallel scan applications.
For small data sets that fit in workgroup, only a single shader pass is needed. For larger data sets, a sequence of shaders is orchestrated as follows:
- One shader does a prefix scan on each workgroup sized chunk of data. It emits a partial prefix sum for each workgroup and single block level sum from each workgroup
- Another instance of the same shader does a prefix scan on the block sums from the previous shader. The end result is a set of block level prefix sums
- A final shader sums the block prefix sums back with the partial prefix sums
For for very large data sets, steps 2 and 3 repeat heirarchically. Each level of summing reduces the data set by a factor of the workgroup size. So three levels handles e.g. 16M elements (256 ** 3) if the workgroup size is 256.
Type parameters
| Name | Type | Description |
|---|---|---|
T | number | Type of elements returned from the scan |
Hierarchy
HasReactive↳
PrefixScan
Implements
Constructors
constructor
• new PrefixScan<T>(args): PrefixScan<T>
Create a new scanner
Type parameters
| Name | Type |
|---|---|
T | number |
Parameters
| Name | Type |
|---|---|
args | PrefixScanArgs |
Returns
PrefixScan<T>
Overrides
HasReactive.constructor
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:130
Properties
binOps
• binOps: BinOpModule
customize the type of scan (e.g. prefix sum on 32 bit floats)
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:85
device
• device: GPUDevice
end index (exclusive) in src buffer (src.length if undefined)
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:121
exclusive
• exclusive: boolean
Inclusive scan accumulates a binary operation across all source elements. Exclusive scan accumulates a binary operation across source elements, using initialValue as the first element and stopping before the final source element.
Default Value
false (inclusive scan).
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:109
forceWorkgroupLength
• Optional forceWorkgroupLength: number
Override to set compute workgroup size e.g. for testing.
Default Value
max workgroup size of the GPUDevice
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:96
initialValue
• Optional initialValue: number
Initial value for exclusive scan
Default Value
0
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:114
label
• Optional label: string
Debug label attached to gpu objects for error reporting
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:91
maxWorkgroups
• Optional maxWorkgroups: number
Override to set max number of workgroups for dispatch e.g. for testing.
Default Value
maxComputeWorkgroupsPerDimension from the GPUDevice
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:101
source
• source: GPUBuffer
Source data to be scanned
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:88
Accessors
result
• get result(): GPUBuffer
Buffer containing results of the scan after the shader has run.
Returns
GPUBuffer
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:154
Methods
commands
▸ commands(commandEncoder): void
Add compute or render passes for this shader to the provided GPUCommandEncoder
Parameters
| Name | Type |
|---|---|
commandEncoder | GPUCommandEncoder |
Returns
void
Implementation of
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:135
destroy
▸ destroy(): void
Release the scanResult buffer for destruction.
Returns
void
Implementation of
Defined in
packages/stoneberry/src/scan/PrefixScan.ts:140
scan
▸ scan(): Promise<number[]>
Execute the prefix scan immediately and copy the results back to the CPU. (results are copied from the PrefixScan.result GPUBuffer)
Returns
Promise<number[]>
the scanned result in an array