diff --git a/utils/solvers/c++/pend.cpp b/utils/solvers/c++/pend.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..e0be4e691eb58bc68e5e785793074f1b129282f4
--- /dev/null
+++ b/utils/solvers/c++/pend.cpp
@@ -0,0 +1,196 @@
+// 1) compile with "g++ pend.cpp -o pend.exe"
+// 2) launch "gmsh pend.exe"
+
+#include <math.h>
+#include <stdio.h>
+#include "onelab.h"
+
+void exportMsh(double le1, double le2)
+{
+ FILE *mshFile = fopen("pend.msh","w");
+ if(!mshFile) return;
+ fprintf(mshFile, "$MeshFormat\n2.2 0 8\n$EndMeshFormat\n");
+ fprintf(mshFile, "$Nodes\n3\n1 0 0 0\n2 0 %f 0\n3 0 %f 0\n$EndNodes\n",
+ -le1, -le1-le2);
+ fprintf(mshFile, "$Elements\n3\n1 1 2 0 1 1 2\n2 1 2 0 1 2 3\n3 15 2 0 2 3\n"
+ "$EndElements\n");
+ fclose(mshFile);
+}
+
+void exportMshOpt()
+{
+ FILE *optFile = fopen("pend.msh.opt", "w");
+ if(!optFile) return;
+ fprintf(optFile, "n = PostProcessing.NbViews - 1;\n");
+ fprintf(optFile, "If(n >= 0)\nView[n].ShowScale = 0;\nView[n].VectorType = 5;\n");
+ fprintf(optFile, "View[n].ExternalView = 0;\nView[n].DisplacementFactor = 1 ;\n");
+ fprintf(optFile, "View[n].PointType = 1;\nView[n].PointSize = 5;\n");
+ fprintf(optFile, "View[n].LineWidth = 2;\nEndIf\n");
+ fclose(optFile);
+}
+
+void exportIter(int iter, double t, double x1, double y1, double x2, double y2)
+{
+ FILE *mshFile = fopen("pend.msh", "a");
+ if(!mshFile) return;
+ fprintf(mshFile, "$NodeData\n1\n\"motion\"\n1\n\t%f\n3\n\t%d\n3\n", t, iter);
+ fprintf(mshFile, "\t3\n\t1 0 0 0\n\t2 %f %f 0\n\t3 %f %f 0\n$EndNodeData\n",
+ x1, y1, x2, y2);
+ fclose(mshFile);
+}
+
+double defineNumber(onelab::client *c, const std::string &name, double value,
+ const std::string &label,
+ const std::map<std::string, std::string> &attributes)
+{
+ std::vector<onelab::number> ns;
+ c->get(ns, name);
+ if(ns.empty()){ // define new parameter
+ onelab::number n(name, value, label);
+ if(attributes.size()) n.setAttributes(attributes);
+ c->set(n);
+ return value;
+ }
+ // return value from server
+ return ns[0].getValue();
+}
+
+void setNumber(onelab::client *c, const std::string &name, double value,
+ double min=0, double max=0, bool visible=true)
+{
+ onelab::number n(name, value);
+ n.setMin(min);
+ n.setMax(max);
+ n.setVisible(visible);
+ c->set(n);
+}
+
+void addNumberChoice(onelab::client *c, const std::string &name, double choice)
+{
+ std::vector<onelab::number> ns;
+ c->get(ns, name);
+ if(ns.size()){
+ std::vector<double> choices = ns[0].getChoices();
+ choices.push_back(choice);
+ ns[0].setChoices(choices);
+ c->set(ns[0]);
+ }
+}
+
+int main(int argc, char **argv)
+{
+ std::string name, address;
+ for(int i = 0; i < argc; i++){
+ if(std::string(argv[i]) == "-onelab" && i + 2 < argc){
+ name = std::string(argv[i + 1]);
+ address = std::string(argv[i + 2]);
+ }
+ }
+
+ if(name.empty() || address.empty()) return 1;
+
+ onelab::remoteNetworkClient *c = new onelab::remoteNetworkClient(name, address);
+
+ std::string action;
+ std::vector<onelab::string> ns;
+ c->get(ns, name + "/Action");
+ if(ns.size()) action = ns[0].getValue();
+
+ double g = 9.8; // acceleration of gravity
+ double m = 0.3; // mass of pendulum balls
+
+ std::map<std::string, std::string> attr;
+
+ double l = defineNumber(c, "Geom/Length", 1.0, "Arm length [m]", attr);
+ double time = defineNumber(c, "Dyna/time", 0., "time [s]", attr);
+ double dt = defineNumber(c, "Dyna/dt", 0.001, "time step [s]", attr);
+ double tmax = defineNumber(c, "Dyna/tmax", 20, "max time [s]", attr);
+ double refresh = defineNumber(c, "Dyna/refresh", 0.05, "refresh interval [s]", attr);
+ attr["Highlight"] = "Pink";
+ double theta0 = defineNumber(c, "Init/theta", 10, "Initial theta angle [deg]", attr);
+ double phi0 = defineNumber(c, "Init/phi", 180, "Initial phi angle [deg]", attr);
+
+ // we're done if we are not in the compute phase
+ if(action != "compute"){
+ delete c;
+ return 0;
+ }
+
+ double l1 = l;
+ double l2 = l;
+ double m1 = m;
+ double m2 = m;
+ double theta = theta0 / 180.*M_PI;
+ double phi = phi0 / 180.*M_PI;
+ double theta_dot = 0.0;
+ double phi_dot = 0.0;
+ double refr = 0.0;
+ int iter = 0;
+ time = 0.0;
+
+ while (time < tmax){
+ double delta = phi - theta;
+ double sdelta = sin(delta);
+ double cdelta = cos(delta);
+ double theta_dot_dot = ( m2*l1*(theta_dot*theta_dot)*sdelta*cdelta
+ + m2*g*sin(phi)*cdelta
+ + m2*l2*(phi_dot*phi_dot)*sdelta
+ - (m1+m2)*g*sin(theta) );
+ theta_dot_dot /= ( (m1+m2)*l1 - m2*l1*(cdelta*cdelta) );
+
+ double phi_dot_dot = ( -m2*l2*(phi_dot*phi_dot)*sdelta*cdelta
+ + (m1+m2)*(g*sin(theta)*cdelta
+ - l1*(theta_dot*theta_dot)*sdelta
+ - g*sin(phi)) );
+ phi_dot_dot /= ( (m1+m2)*l2 - m2*l2*(cdelta*cdelta) );
+
+ double theta_dot = theta_dot + theta_dot_dot*dt;
+ double phi_dot = phi_dot + phi_dot_dot*dt;
+
+ theta = theta + theta_dot*dt;
+ phi = phi + phi_dot*dt;
+
+ double x1 = l1*sin(theta);
+ double y1 = -l1*cos(theta);
+ double x2 = l1*sin(theta) + l2*sin(phi);
+ double y2 = -l1*cos(theta) - l2*cos(phi);
+
+ time += dt;
+ refr += dt;
+
+ exportMshOpt();
+
+ if(refr >= refresh){
+ refr = 0;
+ setNumber(c, name + "/Progress", time, 0, tmax, false);
+ setNumber(c, "Dyna/time", time);
+ setNumber(c, "Solu/phi", phi);
+ addNumberChoice(c, "Solu/phi", phi);
+ setNumber(c, "Solu/theta", theta);
+ addNumberChoice(c, "Solu/theta", theta);
+ setNumber(c, "Solu/phi_dot", phi_dot);
+ addNumberChoice(c, "Solu/phi_dot", phi_dot);
+ setNumber(c, "Solu/theta_dot", theta_dot);
+ addNumberChoice(c, "Solu/theta_dot", theta_dot);
+
+ // ask Gmsh to refresh
+ onelab::string s("Gmsh/Action", "refresh");
+ c->set(s);
+
+ // stop if we are asked to (by Gmsh)
+ c->get(ns, name + "/Action");
+ if(ns.size() && ns[0].getValue() == "stop") break;
+
+ exportMsh(l1, l2);
+ exportIter(iter, time, x1, y1+l1, x2, y2+l1+l2);
+ c->sendMergeFileRequest("pend.msh");
+ iter += 1;
+ }
+ }
+
+ setNumber(c, name + "/Progress", 0, 0, tmax, false);
+
+ delete c;
+
+ return 0;
+}