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Expose simulator RNG seed via SimulatorConfig.seed #27

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Expose simulator RNG seed via SimulatorConfig.seed #27

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36 changes: 25 additions & 11 deletions Network/SimpleDisconnectedNetwork.h
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Original file line number Diff line number Diff line change
Expand Up @@ -602,7 +602,8 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
nrThreads = 1;
else
#endif
if (((method == Simulators::SimulationType::kStatevector || method == Simulators::SimulationType::kPathIntegral) &&
if (((method == Simulators::SimulationType::kStatevector ||
method == Simulators::SimulationType::kPathIntegral) &&
!distCirc->HasOpsAfterMeasurements()) ||
simType == Simulators::SimulatorType::kQuestSim)
nrThreads = 1;
Expand Down Expand Up @@ -786,6 +787,11 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
auto optSim = ChooseBestSimulator(distCirc, shots, nrQubits, nrCbits,
nrCbits, simType, method, executed);

// Seed the executing simulator's terminal sampling RNG, if requested. The
// single-thread path uses optSim directly; in the multi-thread path each
// Clone() derives a distinct deterministic seed from this one.
if (optSim && !seed.empty()) optSim->Configure("seed", seed.c_str());

@greptile-apps greptile-apps Bot Jun 17, 2026

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P1 Job simulators stay unseeded

This only seeds optSim when ChooseBestSimulator() returns one. If no optimized simulator is selected, ExecuteJob creates its own simulator later and only forwards MPS-related options, so the configured seed is dropped and terminal sampling stays random for that execution path.

Prompt To Fix With AI 
This is a comment left during a code review.
Path: Network/SimpleDisconnectedNetwork.h
Line: 793

Comment:
**Job simulators stay unseeded**

This only seeds `optSim` when `ChooseBestSimulator()` returns one. If no optimized simulator is selected, `ExecuteJob` creates its own simulator later and only forwards MPS-related options, so the configured seed is dropped and terminal sampling stays random for that execution path.

How can I resolve this? If you propose a fix, please make it concise.


lastSimulatorType = simType;
lastMethod = method;

Expand Down Expand Up @@ -1001,6 +1007,8 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
(std::string("1") == value || std::string("true") == value);
else if (std::string("max_simulators") == key)
maxSimulators = std::stoull(value);
else if (std::string("seed") == key)
seed = value;

if (simulator) simulator->Configure(key, value);
}
Expand Down Expand Up @@ -1898,8 +1906,10 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {

cloned->SetMPSOptimizeSwaps(GetMPSOptimizeSwaps());

cloned->SetMPSOptimizationBondDimensionThreshold(GetMPSOptimizationBondDimensionThreshold());
cloned->SetMPSOptimizationQubitsNumberThreshold(GetMPSOptimizationQubitsNumberThreshold());
cloned->SetMPSOptimizationBondDimensionThreshold(
GetMPSOptimizationBondDimensionThreshold());
cloned->SetMPSOptimizationQubitsNumberThreshold(
GetMPSOptimizationQubitsNumberThreshold());

cloned->SetLookaheadDepth(GetLookaheadDepth());
cloned->SetLookaheadDepthWithHeuristic(GetLookaheadDepthWithHeuristic());
Expand Down Expand Up @@ -1989,9 +1999,8 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
simulatorTypes.emplace_back(Simulators::SimulatorType::kQCSim,
Simulators::SimulationType::kPauliPropagator);

if (OptimizationSimulatorExists(
Simulators::SimulatorType::kQCSim,
Simulators::SimulationType::kPathIntegral))
if (OptimizationSimulatorExists(Simulators::SimulatorType::kQCSim,
Simulators::SimulationType::kPathIntegral))
simulatorTypes.emplace_back(Simulators::SimulatorType::kQCSim,
Simulators::SimulationType::kPathIntegral);

Expand Down Expand Up @@ -2207,7 +2216,8 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
maxBondDim.empty() ? 0 : std::stoi(maxBondDim);

if (maxBondDim.empty() ||
static_cast<int>(mpsOptimizationBondDimensionThreshold) <= maxBondDimValue) {
static_cast<int>(mpsOptimizationBondDimensionThreshold) <=
maxBondDimValue) {
// need to be sure the circuit is correctly converted
dcirc->ConvertForCutting(); // convert the three qubit gates
auto layers = dcirc->ToMultipleQubitsLayersNoClone();
Expand Down Expand Up @@ -2245,8 +2255,9 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
}
avgTwoQubitGatesPerLayer /= layers.size();

int lookaheadVal = static_cast<int>(4. * avgTwoQubitGatesPerLayer);
if (lookaheadVal > 15) lookaheadVal = 15;
int lookaheadVal = static_cast<int>(4. *
avgTwoQubitGatesPerLayer); if (lookaheadVal > 15) lookaheadVal =
15;

lookaheadDepthLocal =
layers.size() < 8 || nrQubits <= 10 ? 0
Expand All @@ -2269,8 +2280,9 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
*/
lookaheadHeuristicDepthLocal =
layers.size() < 10 || nrQubits <= 10
? 0 : lookaheadDepthLocal - 2;

? 0
: lookaheadDepthLocal - 2;

if (lookaheadHeuristicDepthLocal < 0)
lookaheadHeuristicDepthLocal = 0;

Expand Down Expand Up @@ -2479,6 +2491,8 @@ class SimpleDisconnectedNetwork : public INetwork<Time> {
std::string maxBondDim;
std::string singularValueThreshold;
std::string mpsSample;
std::string seed; /**< User RNG seed for the executing simulator; empty means
non-deterministic (random) sampling. */
bool useDoublePrecision = false;

size_t maxSimulators = QC::QubitRegisterCalculator<>::
Expand Down
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