WelfordUpdate Tiling

Function

Ascend C provides the WelfordUpdate tiling APIs to obtain the tiling parameters required for WelfordUpdate kernel computation.

To obtain the tiling parameters, perform the following steps:

Specifically, use GetWelfordUpdateMaxMinTmpSize to obtain the maximum and minimum temporary space sizes required for WelfordUpdate computation.

To perform WelfordUpdate computation in the kernel, you need to reserve or allocate the temporary space. GetWelfordUpdateMaxMinTmpSize is used to obtain the maximum and minimum temporary space sizes to be reserved or allocated on the host. You can select proper sizes within this range as the tiling parameters and pass them to the kernel.

To ensure correct functions, the temporary space to be reserved or allocated cannot be less than the minimum temporary space.
Within the range between the minimum and maximum, as the temporary space increases, the API computing performance in the kernel can be optimized to some extent. For better performance, reserve or allocate the temporary space based on the actual memory usage.

Prototype

void GetWelfordUpdateMaxMinTmpSize(const ge::Shape& srcShape, const uint32_t typeSizeT, const uint32_t typeSizeU, const bool isReuseSource, const bool isInplace, uint32_t& maxValue, uint32_t& minValue)

Parameters

**Table 1** **GetWelfordUpdateMaxMinTmpSize** API parameters
Parameter	Input/Output	Description
srcShape	Input	Input shape information {rnLength, abLength}. The meanings of rnLength and abLength are the same as those of the WelfordUpdate API.
typeSizeT	Input	Data type size of the input inputX. The unit is byte. For example, if the input data type is half, set this parameter to 2.
typeSizeU	Input	Data type size of the mean and variance (outputMean, outputVariance, inputMean, and inputVariance). The unit is byte. For example, if the input data type is float, set this parameter to 4.
isReuseSource	Input	Whether the source operand can be modified. The value is the same as that of the WelfordUpdate API.
isInplace	Input	Whether the destination operand reuses the source operand. The value is the same as that of the WelfordUpdate API.
maxValue	Output	Maximum size of the temporary space required by WelfordUpdate computation. Any space exceeding this value will not be utilized by the API. Within the range between the minimum and maximum, as the temporary space increases, the API computing performance in the kernel can be optimized to some extent. For better performance, reserve or allocate the temporary space based on the actual memory usage. If the maximum space size is 0, no temporary space is required. NOTE: maxValue is for reference only and may be larger than the remaining space of the Unified Buffer. In this case, select a proper temporary space size based on the remaining space of the Unified Buffer.
minValue	Output	Minimum size of the temporary space required by WelfordUpdate computation. To ensure correct functions, the temporary space to be reserved or allocated during API computation cannot be less than the value of this parameter. If the minimum space size is 0, no temporary space is required.

Returns

None

Restrictions

None

Example

Add the WelfordUpdate Tiling structure parameter to the TilingData structure to function as a field.

BEGIN_TILING_DATA_DEF(WelfordUpdateCustomTilingData) // Register a tiling class and use the tiling name as the input parameter.
  TILING_DATA_FIELD_DEF(uint32_t, inplace); // Add the tiling field to specify whether to reuse input for output.
  TILING_DATA_FIELD_DEF(uint32_t, nLength);
  TILING_DATA_FIELD_DEF(uint32_t, rLength);
  TILING_DATA_FIELD_DEF(uint32_t, abComputeLength);
  TILING_DATA_FIELD_DEF(uint32_t, nRec);
END_TILING_DATA_DEF;
  REGISTER_TILING_DATA_CLASS(WelfordUpdateCustom, WelfordUpdateCustomTilingData) // Add the WelfordUpdateCustomTilingData structure parameter to the TilingData structure.

The tiling implementation function first calls the GetWelfordUpdateMaxMinTmpSize API to obtain the maximum and minimum temporary space sizes required by the WelfordUpdate API to complete computation, sets an appropriate space size based on this range and the actual buffer usage, and then obtains the tiling parameters required by the WelfordUpdate kernel API based on the input shape and available size of computing space.

namespace optiling {
static ge::graphStatus TilingFunc(gert::TilingContext *context)
{
    WelfordUpdateCustomTilingData tiling;
    const gert::RuntimeAttrs *attrs = context->GetAttrs();
    const uint32_t inplace = *(attrs->GetAttrPointer<uint32_t>(0));
    const uint32_t abComputeLength = *(attrs->GetAttrPointer<uint32_t>(1));
    const uint32_t sharedtmpbuffer = *(attrs->GetAttrPointer<uint32_t>(2));

    const gert::StorageShape *x1_shape = context->GetInputShape(1);
    const gert::Shape shape = x1_shape->GetStorageShape();
    auto nLength = shape.GetDim(0);
    auto rLength = shape.GetDim(1);

    std::vector<int64_t> srcDims = {nLength, rLength};
    ge::Shape srcShape(srcDims);

    uint32_t maxTmpsize = 0;
    uint32_t minTmpsize = 0;
    // This example is for reference only. Use GetWelfordUpdateMaxMinTmpSize to obtain the minimum value and pass it to ensure correct functionality. You can pass a proper space size as required.
    AscendC::GetWelfordUpdateMaxMinTmpSize(srcShape, 4, 4, false, false, maxTmpsize, minTmpsize);
    
    ... // Other logic
    context->SetTilingKey(1);
    tiling.SaveToBuffer(context->GetRawTilingData()->GetData(), context->GetRawTilingData()->GetCapacity());
    context->GetRawTilingData()->SetDataSize(tiling.GetDataSize());
    size_t *currentWorkspace = context->GetWorkspaceSizes(1);
    currentWorkspace[0] = 0;
    return ge::GRAPH_SUCCESS;
}
} // namespace optiling

The kernel calls GET_TILING_DATA in the kernel function to obtain tilingData, and then passes the WelfordUpdate tiling information in tilingData to the WelfordUpdate API for computation. For details about the complete example in the kernel, see WelfordUpdate.

extern "C" __global__ __aicore__ void
welford_update_custom(
    GM_ADDR inputX_gm, GM_ADDR mean_gm, GM_ADDR var_gm, GM_ADDR outputMean_gm, GM_ADDR outputVariance_gm, GM_ADDR workspace, GM_ADDR tiling)
{
    GET_TILING_DATA(tilingData, tiling);
    if (TILING_KEY_IS(1))
    {
        if (tilingData.inplace)
        {
            KernelWelfordUpdate<DTYPE_INPUTX, DTYPE_U, true> op; 
            op.Init(inputX_gm, mean_gm, var_gm, outputMean_gm, outputVariance_gm, tilingData.nLength, tilingData.rLength, tilingData.abComputeLength);
            op.Process();
        }
        else
        {
            KernelWelfordUpdate<DTYPE_INPUTX, DTYPE_U, false> op;
            op.Init(inputX_gm, mean_gm, var_gm, outputMean_gm, outputVariance_gm, tilingData.nLength, tilingData.rLength, tilingData.abComputeLength);
            op.Process();
        }
    }
}

Parent topic: Normalization