protected GmresSolver(ILogger logger, INativeMemoryProvider memoryProvider, GmresParams parameters)
{
if (logger == null)
{
throw new ArgumentNullException(nameof(logger));
}
if (memoryProvider == null)
{
throw new ArgumentNullException(nameof(memoryProvider));
}
Logger = logger;
Parameters = parameters;
_nloc = Parameters.LocalDimensionSize;
_m = Parameters.BufferSize;
_dotProducts = Parameters.GramSchmidtType == GramSchmidtType.IterativeClassical ?
new NativeVector(memoryProvider, _m) :
new NativeVector(memoryProvider, 1);
var krylovSize = Parameters.ResidualAtRestart == ResidualAtRestart.ComputeTheTrue ? _m : _m + 1;
_krylovBasis = new FortranMatrix(memoryProvider, _nloc, krylovSize);
_hessenberg = new FortranMatrix(memoryProvider, _m + 1, _m + 1);
_w = new NativeVector(memoryProvider, _nloc);
_r0 = new NativeVector(memoryProvider, _nloc);
_xCurrent = new NativeVector(memoryProvider, _nloc);
_yCurrent = new NativeVector(memoryProvider, _m);
_givensRotSin = new Complex[_m];
_givensRotCos = new double[_m];
}
protected override void ApplyPreconditionerRight(NativeVector src, NativeVector dst, int jH)
{
var col = _precondKrylovBasis.GetColumnVector(jH);
OnRightPreconditionerRequest(new RightPreconditionerRequestEventArgs(src, col));
UnsafeNativeMethods.Zcopy(Parameters.LocalDimensionSize, col.Ptr, dst.Ptr);
}
public static void Sub(NativeVector v1, NativeVector v2, NativeVector result)
{
for (int i = 0; i < result.Length; i++)
{
result[i] = v1[i] - v2[i];
}
}
private double PrepareRestart(NativeVector rhs, NativeVector x, int jH)
{
ConstructCurrentSolution(jH, x);
double beta;
if (Parameters.ResidualAtRestart == ResidualAtRestart.ComputeTheTrue)
{
UnsafeNativeMethods.Zcopy(_nloc, x.Ptr, _w.Ptr);
CalculateMatrixVectorMult(_w, _r0);
NativeVector.Sub(rhs, _r0, _r0);
if (Parameters.Preconditioning != Preconditioning.None)
{
throw new NotImplementedException();
}
UnsafeNativeMethods.Zcopy(_nloc, _r0.Ptr, _w.Ptr);
beta = CalculateVectorNorm(_w);
}
else
{
beta = _hessenberg[_m, _m].Magnitude;
for (int j = _m - 1; j >= 0; j--)
{
_hessenberg[j, _m] = Zero;
Zrot(_hessenberg.GetPointer(j, _m), _hessenberg.GetPointer(j + 1, _m), _givensRotCos[j], -_givensRotSin[j]);
UnsafeNativeMethods.ZgemvNotTrans(_nloc, _m + 1, One, _krylovBasis.Ptr, _hessenberg.GetColumn(_m), Zero, _w.Ptr);
}
}
return(beta);
}
private double CalculateVectorNorm(NativeVector vector)
{
CalculateDotProduct(vector.Ptr, vector.Ptr);
var vectorNorm = Sqrt(_dotProducts[0].Real);
return(vectorNorm);
}
public static void Mult(double alpha, NativeVector v, NativeVector result)
{
for (int i = 0; i < result.Length; i++)
{
result[i] = alpha * v[i];
}
;
}
private void ApplyPreconditionerLeft(NativeVector x, NativeVector result)
{
if (Parameters.Preconditioning != Preconditioning.None)
{
throw new NotImplementedException();
}
UnsafeNativeMethods.Zcopy(_nloc, x.Ptr, result.Ptr);
}
protected override void ApplyPreconditionerRight(NativeVector src, NativeVector dst, int jH)
{
if (Parameters.Preconditioning != Preconditioning.None)
{
throw new NotImplementedException();
}
UnsafeNativeMethods.Zcopy(Parameters.LocalDimensionSize, src.Ptr, dst.Ptr);
}
private void ConstructCurrentSolution(int jH, NativeVector result)
{
UnsafeNativeMethods.Zcopy(jH, _hessenberg.GetColumn(_m), _yCurrent.Ptr);
UnsafeNativeMethods.SimplifiedZtrsv(jH, _hessenberg.Ptr, _m + 1, _yCurrent.Ptr);
CalculateSolutionProjectionToKrylovSubspace(jH);
NativeVector.Add(result, _r0, _xCurrent);
UnsafeNativeMethods.Zcopy(_nloc, _xCurrent.Ptr, result.Ptr);
}
private double FinalActions(int jH, double sPb, NativeVector rhs, NativeVector result)
{
ConstructCurrentSolution(jH, result);
if (Parameters.BackwardErrorChecking != BackwardErrorChecking.CheckArnoldiOnly)
{
return(CheckBackwardError(sPb, rhs));
}
return(-1);
}
private double CheckBackwardError(double sPb, NativeVector rhs)
{
UnsafeNativeMethods.Zcopy(_nloc, _xCurrent.Ptr, _r0.Ptr);
CalculateMatrixVectorMult(_r0, _w);
for (int i = 0; i < _w.Length; i++)
{
_w[i] = rhs[i] - _w[i];
}
var trueNormRes = CalculateVectorNorm(_w);
if (Parameters.Preconditioning != Preconditioning.None)
{
throw new NotImplementedException();
}
var dnormres = trueNormRes;
var be = dnormres / sPb;
if (be >= Parameters.Tolerance)
{
var messageString = $"be = {be}, tolerance = {Parameters.Tolerance}";
if (Parameters.BackwardErrorChecking == BackwardErrorChecking.CheckWithException)
{
throw new BackwardErrorException(messageString);
}
if (Parameters.BackwardErrorChecking == BackwardErrorChecking.CheckWithWarning)
{
Logger.WriteWarning(messageString);
}
}
return(be);
}
private void CalculateMatrixVectorMult(NativeVector x, NativeVector result)
{
var args = new MatrixVectorMultRequestEventArgs(x, result);
OnMatrixVectorMultRequest(args);
}
public MatrixVectorMultRequestEventArgs(NativeVector x, NativeVector result)
{
X = x;
Result = result;
}
public RightPreconditionerRequestEventArgs(NativeVector src, NativeVector dst)
{
Src = src;
Dst = dst;
}
protected abstract void ApplyPreconditionerRight(NativeVector src, NativeVector dst, int jH);
public ResultInfo Solve(NativeVector rightHandSide, NativeVector initialGuess, NativeVector result)
{
return(_flexibleGmres.Solve(rightHandSide, initialGuess, result));
}
public ResultInfo Solve(NativeVector rightHandSide, NativeVector initialGuess, NativeVector result)
{
_iterationCounter = 0;
var bn = CalculateVectorNorm(rightHandSide);
if (CheckRightHandSideForZero(bn))
{
return(ResultInfo.Converged(0, 0, 0));
}
var sb = CalculateScaleFactorsForBackwardErrorUnprecond(bn);
var sPb = CalculateScaleFactorsForBackwardErrorPrecond(bn);
if (Parameters.InitialGuess == InitialGuess.EqualsZero)
{
initialGuess.SetAllValuesToZero();
for (int i = 0; i < _r0.Length; i++)
{
_r0[i] = rightHandSide[i];
}
}
else
{
CalculateMatrixVectorMult(initialGuess, _r0);
for (int i = 0; i < _r0.Length; i++)
{
_r0[i] = rightHandSide[i] - _r0[i];
}
}
ApplyPreconditionerLeft(_r0, _w);
var beta = CalculateVectorNorm(_w);
if (CheckForExactSolution(beta))
{
UnsafeNativeMethods.Zcopy(_nloc, initialGuess.Ptr, result.Ptr);
return(ResultInfo.Converged(0, 0, 1));
}
double bea = -1;
double be = -1;
int iter = 0;
UnsafeNativeMethods.Zcopy(initialGuess.Length, initialGuess.Ptr, result.Ptr);
while (true)
{
NativeVector.Mult(1 / beta, _w, _krylovBasis.GetColumnVector(0));
_hessenberg[0, _m] = beta;
for (int i = 1; i <= _m; i++)
{
_hessenberg[i, _m] = Zero;
}
int jH = 0;
bea = KrylovSubspaceConstruction(bn, ref jH);
if (bea < Parameters.Tolerance)
{
be = FinalActions(jH, sPb, rightHandSide, result);
return(ResultInfo.Converged(bea, be, _iterationCounter));
}
iter++;
if (iter >= Parameters.MaxRepeatNumber)
{
break;
}
beta = PrepareRestart(rightHandSide, result, jH);
}
be = FinalActions(_m, sPb, rightHandSide, result);//ConstructCurrentSolution(_m, result);
return(ResultInfo.NonConverged(bea, be, _iterationCounter));
}
