improve examples

Author: Ithanil

README.md

@@ -46,3 +46,11 @@ Note that we build out-of-tree, so the compiled library and executable files can
 # First steps
 
 You may want to read `doc/user_manual.pdf` to get a quick overview of the libraries functionality. However, it is not guaranteed to be perfectly up-to-date and accurate. Therefore, the best way to get your own code started is by studying the examples in `examples/`. See `examples/README.md` for further guidance.
+
+
+# Multi-threading: MPI
+
+This library supports multi-threaded MC integration with a distributed-memory paradigm, thanks to Message Passing interface (MPI).
+
+To be able to use this feature, just compile the library with a MPI implementation present on your system. The header `MPIMCI.hpp` provides convenient functions
+for using MCI++ with MPI. For example usage, look into example ex2.

build.sh

@@ -4,7 +4,7 @@
 mkdir -p build && cd build
 cmake -DCMAKE_CXX_COMPILER="${CXX_COMPILER}" -DUSER_CXX_FLAGS="${CXX_FLAGS}" -DUSE_COVERAGE="${USE_COVERAGE}" ..
 
-if [ "$1" == "" ]; then
+if [ "$1" = "" ]; then
   make -j$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null)
 else
   make -j$1

examples/CMakeLists.txt

@@ -2,5 +2,4 @@ link_libraries(mci)
 add_executable(ex1.exe ex1/main.cpp)
 if (MPI_FOUND)
   add_executable(ex2.exe ex2/main.cpp)
-  target_link_libraries(ex2.exe ${MPI_CXX_LIBRARIES})
 endif()

examples/ex1/main.cpp

@@ -63,9 +63,9 @@ int main() {
 
     // declare a 1-dimensional integrator
     const int ndim = 1;
-    MCI * mci = new MCI(ndim);
+    MCI mci(ndim);
 
-    cout << "ndim = " << mci->getNDim() << endl;
+    cout << "ndim = " << mci.getNDim() << endl;
 
 
 
@@ -74,34 +74,34 @@ int main() {
     irange[0] = new double[2];
     irange[0][0] = -1.;
     irange[0][1] = 3.;
-    mci->setIRange(irange);
+    mci.setIRange(irange);
 
-    cout << "irange = [ " << mci->getIRange(0, 0) << " ; " << mci->getIRange(0, 1) << " ]" << endl;
+    cout << "irange = [ " << mci.getIRange(0, 0) << " ; " << mci.getIRange(0, 1) << " ]" << endl;
 
 
 
     // initial walker position
-    double * initpos = new double[ndim];
+    double initpos[ndim];
     initpos[0] = -0.5;
-    mci->setX(initpos);
+    mci.setX(initpos);
 
-    cout << "initial walker position = " << mci->getX(0) << endl;
+    cout << "initial walker position = " << mci.getX(0) << endl;
 
 
 
     // initial MRT2 step
-    double * step = new double[ndim];
+    double step[ndim];
     step[0] = 0.5;
-    mci->setMRT2Step(step);
+    mci.setMRT2Step(step);
 
-    cout << "MRT2 step = " << mci->getMRT2Step(0) << endl;
+    cout << "MRT2 step = " << mci.getMRT2Step(0) << endl;
 
 
 
     // target acceptance rate
-    mci->setTargetAcceptanceRate(0.7);
+    mci.setTargetAcceptanceRate(0.7);
 
-    cout << "Acceptance rate = " << mci->getTargetAcceptanceRate() << endl;
+    cout << "Acceptance rate = " << mci.getTargetAcceptanceRate() << endl;
     cout << endl << endl;
 
 
@@ -117,22 +117,22 @@ int main() {
 
     // observable
     MCIObservableFunctionInterface * obs = new Parabola(ndim);
-    mci->addObservable(obs);
+    mci.addObservable(obs);
 
-    cout << "Number of observables set = " << mci->getNObs() << endl;
+    cout << "Number of observables set = " << mci.getNObs() << endl;
 
 
 
     // sampling function
-    cout << "Number of sampling function set = " << mci->getNSampF() << endl;
+    cout << "Number of sampling function set = " << mci.getNSampF() << endl;
 
 
 
     // integrate
     const long Nmc = 1000000;
-    double * average = new double[mci->getNObsDim()];
-    double * error = new double[mci->getNObsDim()];
-    mci->integrate(Nmc, average, error);
+    double average[mci.getNObsDim()];
+    double error[mci.getNObsDim()];
+    mci.integrate(Nmc, average, error);
 
     cout << "The integral gives as result = " << average[0] << "   +-   " << error[0] << endl;
     cout << "--------------------------------------------------------" << endl << endl;
@@ -153,23 +153,23 @@ int main() {
     // observable
     delete obs;
     obs = new NormalizedParabola(ndim);
-    mci->clearObservables();  // we first remove the old observable
-    mci->addObservable(obs);
+    mci.clearObservables();  // we first remove the old observable
+    mci.addObservable(obs);
 
-    cout << "Number of observables set = " << mci->getNObs() << endl;
+    cout << "Number of observables set = " << mci.getNObs() << endl;
 
 
 
     // sampling function
     MCISamplingFunctionInterface * sf = new NormalizedLine(ndim);
-    mci->addSamplingFunction(sf);
+    mci.addSamplingFunction(sf);
 
-    cout << "Number of sampling function set = " << mci->getNSampF() << endl;
+    cout << "Number of sampling function set = " << mci.getNSampF() << endl;
 
 
 
     // integrate
-    mci->integrate(Nmc, average, error);
+    mci.integrate(Nmc, average, error);
 
     cout << "The integral gives as result = " << average[0] << "   +-   " << error[0] << endl;
     cout << "--------------------------------------------------------" << endl << endl;
@@ -183,23 +183,14 @@ int main() {
 
 
     // deallocate
-    delete[] average;
-    delete[] error;
 
     delete sf;
 
     delete obs;
 
-    delete[] step;
-
-    delete[] initpos;
-
     delete[] irange[0];
     delete[] irange;
 
-    delete mci;
-
-
 
     // end
     return 0;

examples/ex2/main.cpp

@@ -64,38 +64,38 @@ int main() {
     }
 
     const int ndim = 1;
-    MCI * mci = new MCI(ndim);
+    MCI mci(ndim);
 
-    if (myrank == 0) cout << "ndim = " << mci->getNDim() << endl;
+    if (myrank == 0) cout << "ndim = " << mci.getNDim() << endl;
 
     // set the integration range to [-1:3]
     double ** irange = new double*[ndim];
     irange[0] = new double[2];
     irange[0][0] = -1.;
     irange[0][1] = 3.;
-    mci->setIRange(irange);
+    mci.setIRange(irange);
 
-    if (myrank == 0) cout << "irange = [ " << mci->getIRange(0, 0) << " ; " << mci->getIRange(0, 1) << " ]" << endl;
+    if (myrank == 0) cout << "irange = [ " << mci.getIRange(0, 0) << " ; " << mci.getIRange(0, 1) << " ]" << endl;
 
     // initial walker position
-    double * initpos = new double[ndim];
+    double initpos[ndim];
     initpos[0] = -0.5;
-    mci->setX(initpos);
+    mci.setX(initpos);
 
-    if (myrank == 0) cout << "initial walker position = " << mci->getX(0) << endl;
+    if (myrank == 0) cout << "initial walker position = " << mci.getX(0) << endl;
 
     // initial MRT2 step
-    double * step = new double[ndim];
+    double step[ndim];
     step[0] = 0.5;
-    mci->setMRT2Step(step);
+    mci.setMRT2Step(step);
 
-    if (myrank == 0) cout << "MRT2 step = " << mci->getMRT2Step(0) << endl;
+    if (myrank == 0) cout << "MRT2 step = " << mci.getMRT2Step(0) << endl;
 
     // target acceptance rate
-    mci->setTargetAcceptanceRate(0.7);
+    mci.setTargetAcceptanceRate(0.7);
 
     if (myrank == 0) {
-        cout << "Acceptance rate = " << mci->getTargetAcceptanceRate() << endl;
+        cout << "Acceptance rate = " << mci.getTargetAcceptanceRate() << endl;
         cout << endl << endl;
 
         // first way of integrating
@@ -106,20 +106,25 @@ int main() {
 
     // observable
     MCIObservableFunctionInterface * obs = new Parabola(ndim);
-    mci->addObservable(obs);
+    mci.addObservable(obs);
 
     if (myrank == 0) {
-        cout << "Number of observables set = " << mci->getNObs() << endl;
+        cout << "Number of observables set = " << mci.getNObs() << endl;
         // sampling function
-        cout << "Number of sampling function set = " << mci->getNSampF() << endl;
+        cout << "Number of sampling function set = " << mci.getNSampF() << endl;
     }
 
     // integrate
     const long Nmc = 1000000;
-    double * average = new double[mci->getNObsDim()];
-    double * error = new double[mci->getNObsDim()];
+    double average[mci.getNObsDim()];
+    double error[mci.getNObsDim()];
 
-    MPIMCI::integrate(mci, Nmc, average, error);
+    // ! set fixed amount of findMRT2 and decorrelation steps    !
+    // ! this is very important for efficient parallel execution !
+    mci.setNfindMRT2steps(50);
+    mci.setNdecorrelationSteps(5000);
+
+    MPIMCI::integrate(&mci, Nmc, average, error);
 
     if (myrank == 0) {
         cout << "The integral gives as result = " << average[0] << "   +-   " << error[0] << endl;
@@ -134,21 +139,21 @@ int main() {
     // observable
     delete obs;
     obs = new NormalizedParabola(ndim);
-    mci->clearObservables();  // we first remove the old observable
-    mci->addObservable(obs);
+    mci.clearObservables();  // we first remove the old observable
+    mci.addObservable(obs);
 
-    if (myrank == 0) cout << "Number of observables set = " << mci->getNObs() << endl;
+    if (myrank == 0) cout << "Number of observables set = " << mci.getNObs() << endl;
 
 
     // sampling function
     MCISamplingFunctionInterface * sf = new NormalizedLine(ndim);
-    mci->addSamplingFunction(sf);
+    mci.addSamplingFunction(sf);
 
-    if (myrank == 0) cout << "Number of sampling function set = " << mci->getNSampF() << endl;
+    if (myrank == 0) cout << "Number of sampling function set = " << mci.getNSampF() << endl;
 
 
     // integrate
-    MPIMCI::integrate(mci, Nmc, average, error);
+    MPIMCI::integrate(&mci, Nmc, average, error);
 
     if (myrank == 0) {
         cout << "The integral gives as result = " << average[0] << "   +-   " << error[0] << endl;
@@ -165,18 +170,9 @@ int main() {
 
     delete obs;
 
-    delete[] step;
-
-    delete[] initpos;
-
     delete[] irange[0];
     delete[] irange;
 
-    delete[] average;
-    delete[] error;
-
-    delete mci;
-
     // finalize MPI
     MPIMCI::finalize();