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Code Releases Activity

Precision change improvements

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Added a new, much faster implementation of precision change that uses (optionally) a precomputed workspace containing pointer offsets that is device resident, such that all lattice copying occurs only on the device and no host<->device transfer is required, other than the pointer table. It also avoids the need to unpack and repack the fields using explicit lane copying. When this new precisionChange is called without a workspace, one will be computed on-the-fly; however it is still considerably faster than the original implementation.

In the special case of using double2 and when the Grids are the same, calls to the new precisionChange will automatically use precisionChangeFast, such that there is a single API call for all precision changes.

Reliable update and mixed-prec multishift have been modified to precompute precision change workspaces

Renamed the original precisionChange as precisionChangeOrig

Fixed incorrect pointer offset bug in copyLane

Added a test and a benchmark for precisionChange

Added a test for reliable update CG
This commit is contained in:
Christopher Kelly
2023-02-21 10:52:42 -05:00
parent 472ed2dd5c
commit 1db58a8acc
7 changed files with 616 additions and 16 deletions
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32
Grid/algorithms/iterative/ConjugateGradientReliableUpdate.h
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@ -48,7 +48,7 @@ public:
LinearOperatorBase<FieldF> &Linop_f;
LinearOperatorBase<FieldD> &Linop_d;
GridBase* SinglePrecGrid;
RealD Delta; //reliable update parameter
RealD Delta; //reliable update parameter. A reliable update is performed when the residual drops by a factor of Delta relative to its value at the last update
//Optional ability to switch to a different linear operator once the tolerance reaches a certain point. Useful for single/half -> single/single
LinearOperatorBase<FieldF> *Linop_fallback;
@ -65,7 +65,9 @@ public:
ErrorOnNoConverge(err_on_no_conv),
DoFinalCleanup(true),
Linop_fallback(NULL)
{};
{
assert(Delta > 0. && Delta < 1. && "Expect 0 < Delta < 1");
};
void setFallbackLinop(LinearOperatorBase<FieldF> &_Linop_fallback, const RealD _fallback_transition_tol){
Linop_fallback = &_Linop_fallback;
@ -116,9 +118,12 @@ public:
}
//Single prec initialization
precisionChangeWorkspace pc_wk_sp_to_dp(src.Grid(), SinglePrecGrid);
precisionChangeWorkspace pc_wk_dp_to_sp(SinglePrecGrid, src.Grid());
FieldF r_f(SinglePrecGrid);
r_f.Checkerboard() = r.Checkerboard();
precisionChange(r_f, r);
precisionChange(r_f, r, pc_wk_dp_to_sp);
FieldF psi_f(r_f);
psi_f = Zero();
@ -134,7 +139,8 @@ public:
GridStopWatch LinalgTimer;
GridStopWatch MatrixTimer;
GridStopWatch SolverTimer;
GridStopWatch PrecChangeTimer;
SolverTimer.Start();
int k = 0;
int l = 0;
@ -173,7 +179,9 @@ public:
// Stopping condition
if (cp <= rsq) {
//Although not written in the paper, I assume that I have to add on the final solution
precisionChange(mmp, psi_f);
PrecChangeTimer.Start();
precisionChange(mmp, psi_f, pc_wk_sp_to_dp);
PrecChangeTimer.Stop();
psi = psi + mmp;
@ -194,7 +202,10 @@ public:
std::cout << GridLogMessage << "\tElapsed " << SolverTimer.Elapsed() <<std::endl;
std::cout << GridLogMessage << "\tMatrix " << MatrixTimer.Elapsed() <<std::endl;
std::cout << GridLogMessage << "\tLinalg " << LinalgTimer.Elapsed() <<std::endl;
std::cout << GridLogMessage << "\tPrecChange " << PrecChangeTimer.Elapsed() <<std::endl;
std::cout << GridLogMessage << "\tPrecChange avg time " << PrecChangeTimer.Elapsed()/(2*l+1) <<std::endl;
IterationsToComplete = k;
ReliableUpdatesPerformed = l;
@ -214,14 +225,21 @@ public:
else if(cp < Delta * MaxResidSinceLastRelUp) { //reliable update
std::cout << GridLogMessage << "ConjugateGradientReliableUpdate "
<< cp << "(residual) < " << Delta << "(Delta) * " << MaxResidSinceLastRelUp << "(MaxResidSinceLastRelUp) on iteration " << k << " : performing reliable update\n";
precisionChange(mmp, psi_f);
PrecChangeTimer.Start();
precisionChange(mmp, psi_f, pc_wk_sp_to_dp);
PrecChangeTimer.Stop();
psi = psi + mmp;
MatrixTimer.Start();
Linop_d.HermOpAndNorm(psi, mmp, d, qq);
MatrixTimer.Stop();
r = src - mmp;
psi_f = Zero();
precisionChange(r_f, r);
PrecChangeTimer.Start();
precisionChange(r_f, r, pc_wk_dp_to_sp);
PrecChangeTimer.Stop();
cp = norm2(r);
MaxResidSinceLastRelUp = cp;