AutoGpu

Note

All Chapel programs automatically use this module by default. An explicit use statement is not necessary.

Warning

The module name ‘AutoGpu’ is unstable.

Automatically included GPU symbols

attribute @gpu.assertEligible

This attribute can be applied to loops to ensure that they are eligible for GPU execution. Unlike @assertOnGpu, this attribute has no execution-time effect. It only asserts that the code could be executed on the GPU, and not that it will be executed.

@gpu.assertEligible
foreach i in 1..128 { /* ... */ }

// variable version (applies to loop expressions and promoted expressions)
@gpu.assertEligible
var A = (foreach i in 1..128 do i*i) + 1;

config param silenceAssertOnGpuWarning = false

This configuration parameter is used to disable warnings that are emitted when @assertOnGpu is used in a non-GPU compilation. Since @assertOnGpu’s execution-time semantics are to halt execution if it is not on the GPU, it will always halt execution when the program is not compiled for the GPU. This is likely an issue, so the warning is emitted by default. However, in case the user is aware of this and wants to silence the warning, they can set this configuration parameter to true.

attribute @assertOnGpu

This attribute can be applied to loops to ensure that they are executed on the GPU. It has the effect of @gpu.assertEligible, halting compilation if the construct it is applied to cannot be executed on the GPU. In addition, this attribute causes an execution-time check to be performed when it is reached, ensuring that the code is executed on the GPU.

@assertOnGpu
foreach i in 1..128 { /* ... */ }

// variable version (applies to loop expressions and promoted expressions)
@assertOnGpu
var A = (foreach i in 1..128 do i*i) + 1;

attribute @gpu.blockSize(blockSize: integral)

This attribute can be applied to loops to specify the GPU block size to use when executing the loop on the GPU.

// loop version
@gpu.blockSize(64)
foreach i in 1..128 { /* ... */ }

// variable version (applies to loop expressions and promoted expressions)
@gpu.blockSize(64)
var A = (foreach i in 1..128 do i*i) + 1;

attribute @gpu.itersPerThread(itersPerThread: integral, param cyclic: bool = false)

This attribute requests that the kernel executes each consecutive numIters iterations of the affected loop sequentially within the same GPU thread. Users must ensure that the arguments to this attribute are positive.

// loop version
@gpu.itersPerThread(4)
foreach i in 1..128 { /* ... */ }

// variable version (applies to loop expressions and promoted expressions)
@gpu.itersPerThread(4)
var A = (foreach i in 1..128 do i*i) + 1;

Specifying the cyclic argument to be true distributes the iterations across GPU threads in cyclic fashion instead of the default block discipline.