internal void Add(Block block)
{
block.VectorIndex = Vector.Count;
Vector.Add(block);
//Debug_AssertConsistency();
Debug.Assert(Vector[block.VectorIndex] == block, "Inconsistent block.VectorIndex");
}
internal bool FilterBlock(Block blockToFilter)
{
// Note: The cache does not try to retain strict accordance with highest violation.
// Doing so lowers the hit rate, probably because if LastModifiedBlock has enough variables,
// then it has enough high violations to flush all other blocks out of the cache, and
// thus the next call to FilterBlock removes all for the current block (which per the following
// paragraph results in calling SearchAllConstraints). As it turns out, it doesn't
// really matter what order we process the constraints in, other than the perf benefit of
// doing the largest violations first, so using the max violation in LastModifiedBlock in this
// situation seems to be good enough to win the tradeoff.
//
// If it becomes necessary to maintain strict "cache always contains the highest violations"
// compliance, then we would have to return false if the filtering removed all elements of
// the cache, because then we wouldn't know if there were any non-blockToFilter-related constraints
// with a higher violation (currently we return true in that case because it is good enough to know
// there is a good chance that this is true). Also, SearchViolationCache would need a verification in
// at least VERIFY mode to verify there are no higher violations in allConstraints.
// Iterate in reverse to remove constraints belonging to LastModifiedBlock.
// Note: Enumerators and .Where are not used because they are much slower.
LowViolation = double.MaxValue;
bool fRet = this.numConstraints > 0;
for (int ii = this.numConstraints - 1; ii >= 0; --ii)
{
var constraint = this.constraints[ii];
// Also remove any constraint that may have been activated by MergeBlocks or marked unsatisfiable
// by Block.Expand.
if ((constraint.Left.Block == blockToFilter) || (constraint.Right.Block == blockToFilter) || constraint.IsActive || constraint.IsUnsatisfiable)
{
// If there are any items after this one, then they are ones we want to keep,
// so swap in the last one in the array before decrementing the count.
if (ii < (this.numConstraints - 1))
{
this.constraints[ii] = this.constraints[this.numConstraints - 1];
}
--this.numConstraints;
}
else
{
#if Inline_Violation
double violation = constraint.Violation; // Inline_Violation
#else // Inline_Violation
double violation = (constraint.Left.ActualPos * constraint.Left.Scale)
+ constraint.Gap
- (constraint.Right.ActualPos * constraint.Right.Scale);
Debug.Assert(constraint.Violation == violation, "LeftConstraints: constraint.Violation must == violation");
#endif // Inline_Violation
if (violation < LowViolation)
{
LowViolation = violation;
}
}
}
if (0 == this.numConstraints)
{
LowViolation = 0.0;
}
return fRet;
}
internal void Remove(Block block)
{
Debug.Assert(Vector[block.VectorIndex] == block, "Inconsistent block.VectorIndex");
Block swapBlock = Vector[Vector.Count - 1];
Vector[block.VectorIndex] = swapBlock;
swapBlock.VectorIndex = block.VectorIndex;
Vector.RemoveAt(Vector.Count - 1);
//Debug_AssertConsistency();
Debug.Assert((0 == Vector.Count) || (block == swapBlock) || (Vector[swapBlock.VectorIndex] == swapBlock),
"Inconsistent swapBlock.VectorIndex");
Debug.Assert((0 == Vector.Count) || (Vector[Vector.Count - 1].VectorIndex == (Vector.Count - 1)),
"Inconsistent finalBlock.VectorIndex");
}
private bool Project()
{
if (0 == this.numberOfConstraints)
{
// We are here for the neighbours-only case.
return false;
}
// Get the maximum violation (the Constraint with the biggest difference between the
// required gap between its two variables vs. their actual relative positions).
// If there is no violation, we're done (although SplitBlocks may change things so
// we have to go again).
this.violationCache.Clear();
this.lastModifiedBlock = null;
bool useViolationCache = this.allBlocks.Count > this.violationCacheMinBlockCutoff;
// The first iteration gets the first violated constraint.
int cIterations = 1;
double maxViolation;
Constraint maxViolatedConstraint = GetMaxViolatedConstraint(out maxViolation, useViolationCache);
if (null == maxViolatedConstraint)
{
#if VERBOSE
Console.WriteLine("Project() found no violations");
#endif // VERBOSE
return false;
}
// We have at least one violation, so process them until there are no more.
while (null != maxViolatedConstraint)
{
Debug.Assert(!maxViolatedConstraint.IsUnsatisfiable, "maxViolatedConstraint should not be unsatisfiable");
Debug.Assert(!maxViolatedConstraint.IsEquality, "maxViolatedConstraint should not be equality");
#if VERBOSE
Console.WriteLine("MaxVio: {0}", maxViolatedConstraint);
// Write a line in satisfy_inc format to compare:
// most violated is: (45=9.73427)+3<=(51=0.456531)(-12.2777) [chop off lm as it's uninitialized in satisfy_inc output]
Console.WriteLine(" most violated is: ({0}={1:F6})+{2:F0}<=({3}={4:F6})({5:F6})",
maxViolatedConstraint.Left.Name, maxViolatedConstraint.Left.ActualPos, maxViolatedConstraint.Gap,
maxViolatedConstraint.Right.Name, maxViolatedConstraint.Right.ActualPos, maxViolatedConstraint.Violation);
#endif // VERBOSE
// Perf note: Variables (and Blocks) use the default Object.Equals implementation, which is
// simply ReferenceEquals for reference types.
if (maxViolatedConstraint.Left.Block == maxViolatedConstraint.Right.Block)
{
maxViolatedConstraint.Left.Block.Expand(maxViolatedConstraint);
if (maxViolatedConstraint.IsUnsatisfiable)
{
this.violationCache.Clear(); // We're confusing the lineage of lastModifiedBlock
}
this.lastModifiedBlock = maxViolatedConstraint.Left.Block;
}
else
{
// The variables are in different blocks so merge the blocks.
this.lastModifiedBlock = MergeBlocks(maxViolatedConstraint);
}
#if VERBOSE
DumpCost();
#endif // VERBOSE
// Note that aborting here does not guarantee a feasible state.
if (this.solverParams.InnerProjectIterationsLimit > 0)
{
if (cIterations >= this.solverParams.InnerProjectIterationsLimit)
{
#if VERBOSE
Console.WriteLine("PostProject aborting due to max inner iterations: max {0}",
solverParams.InnerProjectIterationsLimit);
#endif // VERBOSE
this.solverSolution.InnerProjectIterationsLimitExceeded = true;
break;
}
}
// Now we've potentially changed one or many variables' positions so recalculate the max violation.
useViolationCache = this.allBlocks.Count > this.violationCacheMinBlockCutoff;
if (!useViolationCache)
{
this.violationCache.Clear();
}
++cIterations;
maxViolatedConstraint = GetMaxViolatedConstraint(out maxViolation, useViolationCache);
} // endwhile violations exist
this.solverSolution.InnerProjectIterationsTotal += cIterations;
if (this.solverSolution.MaxInnerProjectIterations < cIterations)
{
this.solverSolution.MaxInnerProjectIterations = cIterations;
}
if (this.solverSolution.MinInnerProjectIterations > cIterations)
{
this.solverSolution.MinInnerProjectIterations = cIterations;
}
// If we got here, we had at least one violation.
this.allConstraints.Debug_AssertConsistency();
return true;
} // end Project()
private void ReinitializeBlocks()
{
// For Qpsc we want to discard the previous block structure, because it did not consider
// neighbors, and the gradient may want to pull things in an entirely different way.
// We must also do this for a re-Solve that updated the gap of an equality constraint.
var oldBlocks = this.allBlocks.Vector.ToArray();
this.allBlocks.Vector.Clear();
#if VERIFY || VERBOSE
this.nextNewBlockOrdinal = 0;
#endif // VERIFY || VERBOSE
foreach (Block oldBlock in oldBlocks)
{
foreach (Variable variable in oldBlock.Variables)
{
variable.Reinitialize();
var newBlock = new Block(variable, this.allConstraints
#if VERIFY || VERBOSE
, ref this.nextNewBlockOrdinal
#endif // VERIFY || VERBOSE
);
this.allBlocks.Add(newBlock);
}
}
this.allConstraints.Reinitialize();
this.violationCache.Clear();
}
/// <summary>
/// Add a Variable (for example, wrapping a node on one axis of the graph) to the Solver.
/// </summary>
/// <param name="userData">a tag or other user data - can be null</param>
/// <param name="desiredPos">The position of the variable, such as the coordinate of a node along one axis.</param>
/// <param name="weight">The weight of the variable (makes it less likely to move if the weight is high).</param>
/// <param name="scale">The scale of the variable, for improving convergence.</param>
/// <returns>The created variable</returns>
public Variable AddVariable(Object userData, double desiredPos, double weight, double scale)
{
// @@DCR "Incremental Solving": For now we disallow this; if we support it, we'll need to
// retain loadedVariablesAndConstraintLists, store up the added Variables (TryGetValue and if that fails add
// the existing variable, then iterate through variables with new Constraints and replace the arrays.
// Also remember to check for emptyConstraintList - don't add to it.
if (!this.allConstraints.IsEmpty)
{
throw new InvalidOperationException(
#if DEBUG
"Cannot add Variables or Constraints once Solve() has been called"
#endif // DEBUG
);
}
var varNew = new Variable(this.nextVariableOrdinal++, userData, desiredPos, weight, scale);
var block = new Block(varNew, this.allConstraints
#if VERIFY || VERBOSE
, ref this.nextNewBlockOrdinal
#endif // VERIFY || VERBOSE
);
varNew.Block = block;
this.allBlocks.Add(block);
++this.numberOfVariables;
// Initialize the variable in the dictionary with a null list and zero left constraints.
this.loadedVariablesAndConstraintLists[varNew] = new ConstraintListForVariable(new List<Constraint>(), 0);
return varNew;
} // end AddVariable()
internal Block SplitOnConstraint(Constraint constraintToSplit
#if VERIFY || VERBOSE
, ref uint blockId
#endif // VERIFY || VERBOSE
)
{
// We have a split point. Remove that constraint from our active list and transfer it and all
// variables to its right to a new block. As mentioned above, all variables and associated
// constraints in the block are active, and the block split and recalc of reference positions
// doesn't change the actual positions of any variables.
this.allConstraints.DeactivateConstraint(constraintToSplit);
var newSplitBlock = new Block(null, this.allConstraints
#if VERIFY || VERBOSE
, ref blockId
#endif // VERIFY || VERBOSE
);
// Transfer the connected variables. This has the side-effect of moving the associated active
// constraints as well (because they are carried in the variables' LeftConstraints).
// This must include not only minLagrangianConstraint.Right and those to its right, but also
// those to its left that are connected to it by active constraints - because connected variables
// must be within a single a block. Since we are splitting the constraint, there will be at least
// one variable (minLagrangianConstraint.Left) in the current block when we're done. Because the active
// constraints form a tree, we won't have a situation where minLagrangianConstraint.Left is
// also the .Right of a constraint of a variable to the left of varRight.
// minLagrangianConstraint.Left is "already evaluated" because we don't want the path evaluation to
// back up to it (because we're splitting minLagrangianConstraint by deactivating it).
this.DebugVerifyBlockConnectivity();
this.TransferConnectedVariables(newSplitBlock, constraintToSplit.Right, constraintToSplit.Left);
if (newSplitBlock.Variables.Count > 0)
{
// We may have removed the first variable so fully recalculate the reference position.
this.UpdateReferencePos();
// The new block's sums were not updated as its variables were added directly to its
// variables list, so fully recalculate.
newSplitBlock.UpdateReferencePos();
this.DebugVerifyBlockConnectivity();
newSplitBlock.DebugVerifyBlockConnectivity();
#if VERBOSE
Console.WriteLine("Block.Split Result: {0} {1}", this, newSplitBlock);
Console.WriteLine("Old block: {0}", this);
this.DumpState(null /* no prefix */);
Console.WriteLine("New block: {0}", newSplitBlock);
newSplitBlock.DumpState(null /* no prefix */);
#endif // VERBOSE
}
else
{
// If there were unsatisfiable constraints, we may have tried to transfer all variables;
// in that case we simply ignored the transfer operation and left all variables in 'this' block.
// Return NULL so Solver.SplitBlocks knows we didn't split.
newSplitBlock = null;
#if VERBOSE
Console.WriteLine("Block.Split Result: all variables would be moved, so skipping");
this.DumpState(null /* no prefix */);
#endif // VERBOSE
}
return newSplitBlock;
} // end Split()
internal void Debug_PostMerge(Block blockFrom)
{
#if DEBUG
// If blockFrom's DfDv-cycle detection value was higher than ours, we need to set ours to
// that value, to avoid running into stale values.
if (blockFrom.idDfDv > this.idDfDv)
{
this.idDfDv = blockFrom.idDfDv;
}
#endif // DEBUG
}
void TransferConnectedVariables(Block newSplitBlock, Variable varToEval, Variable varDoneEval)
{
GetConnectedVariables(newSplitBlock.Variables, varToEval, varDoneEval);
int numVarsToMove = newSplitBlock.Variables.Count; // cache for perf
// The constraints transferred to the new block need to have any stale cycle-detection values cleared out.
newSplitBlock.Debug_ClearDfDv(true /* forceFull */);
// Avoid the creation of an inner loop on List<T>.Remove (which does linear scan and shift
// to preserve the order of members). We don't care about variable ordering within the block
// so we can just repeatedly swap in the end one over whichever we're removing.
for (int moveIndex = 0; moveIndex < numVarsToMove; ++moveIndex)
{
newSplitBlock.Variables[moveIndex].Block = newSplitBlock;
}
// Now iterate from the end and swap in the last one we'll keep over the ones we'll remove.
int lastKeepIndex = this.Variables.Count - 1;
for (int currentIndex = this.Variables.Count - 1; currentIndex >= 0; --currentIndex)
{
Variable currentVariable = this.Variables[currentIndex];
if (currentVariable.Block == newSplitBlock)
{
if (currentIndex < lastKeepIndex)
{
// Swap in the one from the end.
this.Variables[currentIndex] = this.Variables[lastKeepIndex];
}
--lastKeepIndex;
}
} // end for each var to keep
// Now remove the end slots we're not keeping. lastKeepIndex is -1 if we are removing all variables.
Debug.Assert(numVarsToMove == this.Variables.Count - lastKeepIndex - 1, "variable should not be found twice (probable cycle-detection problem");
this.Variables.RemoveRange(lastKeepIndex + 1, this.Variables.Count - lastKeepIndex - 1);
if (0 == this.Variables.Count)
{
// This is probably due to unsatisfiable constraints; we've transferred all the variables,
// so just don't split at all; move the variables back into the current block rather than
// leaving an empty block in the list. Caller will detect the empty newSplitBlock and ignore it.
for (int moveIndex = 0; moveIndex < numVarsToMove; ++moveIndex)
{
var variableToMove = newSplitBlock.Variables[moveIndex];
this.Variables.Add(variableToMove);
variableToMove.Block = this;
}
newSplitBlock.Variables.Clear();
}
} // end TransferConnectedVariables()
