Make QHybrid default engine type

README.md

@@ -1,6 +1,6 @@
 # Qrack
 
-[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.3785646.svg)](https://zenodo.org/badge/latestdoi/114947047) [![Qrack Build Status](https://api.travis-ci.org/vm6502q/qrack.svg?branch=master)](https://travis-ci.org/vm6502q/qrack/builds) [![Mentioned in Awesome awesome-quantum-computing](https://awesome.re/mentioned-badge.svg)](https://github.com/desireevl/awesome-quantum-computing)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.3842287.svg)](https://doi.org/10.5281/zenodo.3842287) [![Qrack Build Status](https://api.travis-ci.org/vm6502q/qrack.svg?branch=master)](https://travis-ci.org/vm6502q/qrack/builds) [![Mentioned in Awesome awesome-quantum-computing](https://awesome.re/mentioned-badge.svg)](https://github.com/desireevl/awesome-quantum-computing)
 
 [![Unitary Fund](https://img.shields.io/badge/Supported%20By-UNITARY%20FUND-brightgreen.svg?style=for-the-badge)](http://unitary.fund)
 

include/qfactory.hpp

@@ -45,7 +45,7 @@ QInterfacePtr CreateQuantumInterface(
     case QINTERFACE_HYBRID:
         return std::make_shared<QHybrid>(args...);
     case QINTERFACE_QUNIT_MULTI:
-        return std::make_shared<QUnitMulti>(subengine1, args...);
+        return std::make_shared<QUnitMulti>(args...);
 #endif
     default:
         return NULL;
@@ -70,7 +70,7 @@ QInterfacePtr CreateQuantumInterface(QInterfaceEngine engine, QInterfaceEngine s
     case QINTERFACE_HYBRID:
         return std::make_shared<QHybrid>(args...);
     case QINTERFACE_QUNIT_MULTI:
-        return std::make_shared<QUnitMulti>(subengine, args...);
+        return std::make_shared<QUnitMulti>(args...);
 #endif
     default:
         return NULL;
@@ -87,6 +87,8 @@ template <typename... Ts> QInterfacePtr CreateQuantumInterface(QInterfaceEngine
         return std::make_shared<QEngineOCL>(args...);
     case QINTERFACE_HYBRID:
         return std::make_shared<QHybrid>(args...);
+    case QINTERFACE_QUNIT_MULTI:
+        return std::make_shared<QUnitMulti>(args...);
 #endif
     default:
         return NULL;

include/qhybrid.hpp

@@ -39,7 +39,7 @@ class QHybrid : public QInterface {
     QHybrid(bitLenInt qBitCount, bitCapInt initState = 0, qrack_rand_gen_ptr rgp = nullptr,
         complex phaseFac = CMPLX_DEFAULT_ARG, bool doNorm = true, bool randomGlobalPhase = true,
         bool useHostMem = false, int deviceId = -1, bool useHardwareRNG = true, bool useSparseStateVec = false,
-        real1 norm_thresh = REAL1_DEFAULT_ARG, std::vector<int> ignored = {}, bitLenInt qubitThreshold = 13);
+        real1 norm_thresh = REAL1_DEFAULT_ARG, std::vector<int> ignored = {}, bitLenInt qubitThreshold = 0);
 
     QEnginePtr MakeEngine(bool isOpenCL, bitCapInt initState = 0);
 
@@ -51,6 +51,11 @@ class QHybrid : public QInterface {
         engine->SetConcurrency(concurrency);
     }
 
+    /**
+     * Switches between CPU and GPU used modes. (This will not incur a performance penalty, if the chosen mode matches
+     * the current mode.) Mode switching happens automatically when qubit counts change, but Compose() and Decompose()
+     * might leave their destination QInterface parameters in the opposite mode.
+     */
     virtual void SwitchModes(bool useGpu)
     {
         if (!isGpu && useGpu) {

include/qinterface.hpp

@@ -118,7 +118,7 @@ enum QInterfaceEngine {
 
     QINTERFACE_FIRST = QINTERFACE_CPU,
 #if ENABLE_OPENCL
-    QINTERFACE_OPTIMAL = QINTERFACE_OPENCL,
+    QINTERFACE_OPTIMAL = QINTERFACE_HYBRID,
 #else
     QINTERFACE_OPTIMAL = QINTERFACE_CPU,
 #endif

include/qunitmulti.hpp

@@ -68,15 +68,7 @@ class QUnitMulti : public QUnit, public ParallelFor {
     std::vector<DeviceInfo> deviceList;
 
 public:
-    QUnitMulti(bitLenInt qBitCount, bitCapInt initState, qrack_rand_gen_ptr rgp, complex phaseFac, bool doNorm,
-        bool randomGlobalPhase, bool useHostMem, int deviceID, bool useHardwareRNG, bool useSparseStateVec,
-        real1 norm_thresh, std::vector<int> devList, bitLenInt qubitThreshold)
-        : QUnitMulti(QINTERFACE_OPENCL, qBitCount, initState, rgp, phaseFac, doNorm, randomGlobalPhase, useHostMem, -1,
-              useHardwareRNG, qubitThreshold)
-    {
-    }
-
-    QUnitMulti(QInterfaceEngine eng, bitLenInt qBitCount, bitCapInt initState = 0, qrack_rand_gen_ptr rgp = nullptr,
+    QUnitMulti(bitLenInt qBitCount, bitCapInt initState = 0, qrack_rand_gen_ptr rgp = nullptr,
         complex phaseFac = CMPLX_DEFAULT_ARG, bool doNorm = true, bool randomGlobalPhase = true,
         bool useHostMem = false, int deviceID = -1, bool useHardwareRNG = true, bool useSparseStateVec = false,
         real1 norm_thresh = REAL1_DEFAULT_ARG, std::vector<int> devList = {}, bitLenInt qubitThreshold = 0);

src/qhybrid.cpp

@@ -25,10 +25,12 @@ QHybrid::QHybrid(bitLenInt qBitCount, bitCapInt initState, qrack_rand_gen_ptr rg
     , useHostRam(useHostMem)
     , useRDRAND(useHardwareRNG)
     , isSparse(useSparseStateVec)
-    , isGpu(qubitCount >= qubitThreshold)
 {
     concurrency = std::thread::hardware_concurrency();
-    thresholdQubits = qubitThreshold ? qubitThreshold : log2(concurrency) + QBCAPPOW;
+    thresholdQubits = (qubitThreshold != 0)
+        ? qubitThreshold
+        : (concurrency == 1 ? PSTRIDEPOW : (log2(concurrency - 1) + PSTRIDEPOW + 1));
+    isGpu = (qubitCount >= thresholdQubits);
     engine = MakeEngine(qubitCount >= thresholdQubits, initState);
 }
 

src/qunitmulti.cpp

@@ -17,10 +17,10 @@
 
 namespace Qrack {
 
-QUnitMulti::QUnitMulti(QInterfaceEngine eng, bitLenInt qBitCount, bitCapInt initState, qrack_rand_gen_ptr rgp,
-    complex phaseFac, bool doNorm, bool randomGlobalPhase, bool useHostMem, int deviceID, bool useHardwareRNG,
-    bool useSparseStateVec, real1 norm_thresh, std::vector<int> devList, bitLenInt qubitThreshold)
-    : QUnit(eng, QINTERFACE_OPENCL, qBitCount, initState, rgp, phaseFac, doNorm, randomGlobalPhase, useHostMem, -1,
+QUnitMulti::QUnitMulti(bitLenInt qBitCount, bitCapInt initState, qrack_rand_gen_ptr rgp, complex phaseFac, bool doNorm,
+    bool randomGlobalPhase, bool useHostMem, int deviceID, bool useHardwareRNG, bool useSparseStateVec,
+    real1 norm_thresh, std::vector<int> devList, bitLenInt qubitThreshold)
+    : QUnit(QINTERFACE_OPENCL, qBitCount, initState, rgp, phaseFac, doNorm, randomGlobalPhase, useHostMem, -1,
           useHardwareRNG, useSparseStateVec, norm_thresh, devList, qubitThreshold)
 {
     // Notice that this constructor always passes QINTERFACE_OPENCL to the QUnit constructor. For QUnitMulti, the
@@ -199,7 +199,7 @@ QInterfacePtr QUnitMulti::Clone()
     EndAllEmulation();
 
     QUnitMultiPtr copyPtr = std::make_shared<QUnitMulti>(
-        engine, qubitCount, 0, rand_generator, complex(ONE_R1, ZERO_R1), doNormalize, randGlobalPhase, useHostRam);
+        qubitCount, 0, rand_generator, complex(ONE_R1, ZERO_R1), doNormalize, randGlobalPhase, useHostRam);
 
     return CloneBody(copyPtr);
 }