/// <summary>
/// Do BB step, updates alpha and "w" vector
/// </summary>
/// <remarks>
/// This method has many side effects:
/// 1. copies data on device from alphaPtr to alphaTmpPtr
/// 2. sets values in deltas array, which are differences between new alpha and old alphas
/// 3. alphaTmpPtr stores new updated alphas
/// </remarks>
/// <param name="step"></param>
/// <param name="sub_prob"></param>
private void DoBBstep(float step, Problem <SparseVec> sub_prob)
{
int blocks = (sub_prob.Elements.Length + threadsPerBlock - 1) / threadsPerBlock;
/*
* Update alpha
*
* 1. copy alpha to alphaTmp
* 2. copy step into device constant
* 3. set parameters
*
*/
cuda.CopyDeviceToDevice(alphaPtr, alphaTmpPtr, alphaMemSize);
float[] stepData = new float[] { step };
cuda.CopyHostToDevice(stepBBPtr, stepData);
cuda.SetParameter(cuFuncUpdateAlpha, gradParamOffsetInUpdateAlpha, gradPtr.Pointer);
cuda.SetParameter(cuFuncUpdateAlpha, alphaParamOffsetInUpdateAlpha, alphaTmpPtr.Pointer);
cuda.Launch(cuFuncUpdateAlpha, blocks, 1);
//float[] updatedAlpha = new float[sub_prob.ElementsCount];
//cuda.CopyDeviceToHost(alphaTmpPtr, updatedAlpha);
//float[] updatedDeltas = new float[sub_prob.ElementsCount];
//cuda.CopyDeviceToHost(deltasPtr, updatedDeltas);
/*
* Update w - based on aplha deltas
*
*/
int bpgUpdateW = (sub_prob.Elements[0].Dim + threadsPerBlock - 1) / threadsPerBlock;
cuda.CopyDeviceToDevice(wVecPtr, wTempVecPtr, wVecMemSize);
cuda.SetParameter(cuFuncUpdateW, wVecParamOffsetInUpdateW, wTempVecPtr.Pointer);
cuda.Launch(cuFuncUpdateW, bpgUpdateW, 1);
//float[] wTest = new float[sub_prob.FeaturesCount];
//cuda.CopyDeviceToHost(wTempVecPtr, wTest);
}
