/// <summary>
/// Compares Time field of two nodes. Also updates MaxLowerBound and MinUpperBound.
/// </summary>
/// <returns>Result of comparison of Time field of QubitTimeNode</returns>
public int Compare(QubitTimeNode a, QubitTimeNode b)
{
// Note that comparison of a and b nodes to Sample is "by reference" in this function.
int result = ComplexTime.Compare(a.Time, b.Time);
if (result > 0)
{
if (a == Sample && b != Sample)
{
MaxLowerBound = ComplexTime.Max(MaxLowerBound, b.Time);
}
else if (a != Sample && b == Sample)
{
MinUpperBound = ComplexTime.Min(MinUpperBound, a.Time);
}
}
else if (result < 0)
{
if (a == Sample && b != Sample)
{
MinUpperBound = ComplexTime.Min(MinUpperBound, b.Time);
}
else if (a != Sample && b == Sample)
{
MaxLowerBound = ComplexTime.Max(MaxLowerBound, a.Time);
}
}
else
{
// We found the value if one argument is the sample and the other is not.
if ((a == Sample) != (b == Sample))
{
MaxLowerBound = b.Time;
MinUpperBound = b.Time;
}
}
return(result);
}
/// <summary>
/// Compare objects assuming they are QubitTimeMetrics. Compare by StartTime.
/// </summary>
private static int CompareAsQubitTimeMetricsByStartTime(object x, object y)
{
return(ComplexTime.Compare(((QubitTimeMetrics)x).StartTime, ((QubitTimeMetrics)y).StartTime));
}
public void OnRelease(object[] qubitsTraceData)
{
OperationCallRecord opRec = operationCallStack.Peek();
opRec.ReleasedQubitsAvailableTime = Max(
opRec.ReleasedQubitsAvailableTime,
MaxAvailableTime(qubitsTraceData.Cast <QubitTimeMetrics>()));
if (optimizeDepth)
{
// Performing width computation and applying reuse heuristics.
// First we fix busy time periods for all qubits involved.
foreach (QubitTimeMetrics q in qubitsTraceData.Cast <QubitTimeMetrics>())
{
// If qubit is not fixed in time we fix it at zero.
if (q.StartTime.IsEqualTo(ComplexTime.MinValue))
{
q.StartTime = ComplexTime.Zero;
}
}
// Then we sort qubits ascending by the start of busy time. This would result in optimal reuse if:
// (1) We were not allowed to move gates in time.
// (2) We were sorting all qubits of the cirquit, not just this block.
// In reality these statements aren't true, so this is only a heuristic rather than the optimal reuse of qubits.
Array.Sort(qubitsTraceData, CompareAsQubitTimeMetricsByStartTime);
// Reuse qubits if possible or increase count of qubits used.
foreach (QubitTimeMetrics q in qubitsTraceData.Cast <QubitTimeMetrics>())
{
// If qubit wasn't used in any gate. We don't allocate it.
if (q.EndTime.IsEqualTo(ComplexTime.Zero))
{
continue;
}
// Then we find if we can reuse existing qubits.
bool reuseExistingAfterNew = qubitStartTimes.FindBound(q.EndTime, getLowerBound: false, out ComplexTime existingStart);
bool reuseNewAfterExising = qubitEndTimes.FindBound(q.StartTime, getLowerBound: true, out ComplexTime existingEnd);
if (reuseNewAfterExising && reuseExistingAfterNew)
{
// If we can do both, see which reuse creates a shorter gap and leave it for reuse.
if (ComplexTime.Compare(q.StartTime.Subtract(existingEnd), existingStart.Subtract(q.EndTime)) > 0)
{
reuseNewAfterExising = false;
}
else
{
reuseExistingAfterNew = false;
}
}
if (reuseNewAfterExising)
{
// If we place new qubit after existing - update end time of existing qubit
long idToReuse = qubitEndTimes.Remove(existingEnd);
qubitEndTimes.Add(idToReuse, q.EndTime);
}
else if (reuseExistingAfterNew)
{
// If we place new qubit before existing - update start time of existing qubit
long idToReuse = qubitStartTimes.Remove(existingStart);
qubitStartTimes.Add(idToReuse, q.StartTime);
}
else
{
// We cannot reuse existing qubits. Use new qubit.
long id = maxQubitId;
maxQubitId++;
qubitStartTimes.Add(id, q.StartTime);
qubitEndTimes.Add(id, q.EndTime);
}
}
}
}
public void OnRelease(object[] qubitsTraceData)
{
OperationCallRecord opRec = operationCallStack.Peek();
opRec.ReleasedQubitsAvailableTime = Max(
opRec.ReleasedQubitsAvailableTime,
MaxAvailableTime(qubitsTraceData.Cast <QubitTimeMetrics>()));
if (optimizeDepth)
{
// Doing width reuse heuristics and width computation.
foreach (QubitTimeMetrics q in qubitsTraceData.Cast <QubitTimeMetrics>())
{
// If qubit wasn't used in any gate. We don't allocate it.
if (q.EndTime.IsEqualTo(ComplexTime.Zero))
{
continue;
}
// If qubit is not fixed in time we fix it at zero.
if (q.StartTime.IsEqualTo(ComplexTime.MinValue))
{
q.StartTime = ComplexTime.Zero;
}
// Then we find if we can reuse existing qubits.
bool reuseExistingAfterNew = qubitStartTimes.FindBound(q.EndTime, getLowerBound: false, out ComplexTime existingStart);
bool reuseNewAfterExising = qubitEndTimes.FindBound(q.StartTime, getLowerBound: true, out ComplexTime existingEnd);
if (reuseNewAfterExising && reuseExistingAfterNew)
{
// If we can do both, see which reuse creates a shorter gap and leave it for reuse.
if (ComplexTime.Compare(q.StartTime.Subtract(existingEnd), existingStart.Subtract(q.EndTime)) > 0)
{
reuseNewAfterExising = false;
}
else
{
reuseExistingAfterNew = false;
}
}
if (reuseNewAfterExising)
{
// If we place new qubit after existing - update end time of existing qubit
long idToReuse = qubitEndTimes.Remove(existingEnd);
qubitEndTimes.Add(idToReuse, q.EndTime);
}
else if (reuseExistingAfterNew)
{
// If we place new qubit before existing - update start time of existing qubit
long idToReuse = qubitStartTimes.Remove(existingStart);
qubitStartTimes.Add(idToReuse, q.StartTime);
}
else
{
// We cannot reuse existing qubits. Use new qubit.
long id = maxQubitId;
maxQubitId++;
qubitStartTimes.Add(id, q.StartTime);
qubitEndTimes.Add(id, q.EndTime);
}
}
}
}
