new: enable cascaded multi-grids... incl. an example

FDTD/engine.cpp

@@ -48,7 +48,6 @@ Engine::~Engine()
 
 void Engine::Init()
 {
-	Reset();
 	numTS = 0;
 	volt = Create_N_3DArray<FDTD_FLOAT>(numLines);
 	curr = Create_N_3DArray<FDTD_FLOAT>(numLines);

FDTD/engine_cylindermultigrid.cpp

@@ -36,15 +36,27 @@ Engine_CylinderMultiGrid::Engine_CylinderMultiGrid(const Operator_CylinderMultiG
 	m_WaitOnChild = new boost::barrier(2);
 	m_WaitOnSync = new boost::barrier(2);
 
-	Engine* eng = op->GetInnerOperator()->CreateEngine();
-	m_InnerEngine = dynamic_cast<Engine_Multithread*>(eng);
-
 	m_Eng_Ext_MG = new Engine_Ext_CylinderMultiGrid(NULL,true);
 	m_Eng_Ext_MG->SetBarrier(m_WaitOnBase, m_WaitOnChild, m_WaitOnSync);
 	m_Eng_Ext_MG->SetEngine(this);
-	m_InnerEng_Ext_MG = new Engine_Ext_CylinderMultiGrid(NULL,false);
+
+	Engine* eng = op->GetInnerOperator()->CreateEngine();
+	m_InnerEngine = dynamic_cast<Engine_Multithread*>(eng);
+
+	Engine_Ext_CylinderMultiGrid* m_InnerEng_Ext_MG = new Engine_Ext_CylinderMultiGrid(NULL,false);
 	m_InnerEng_Ext_MG->SetBarrier(m_WaitOnBase, m_WaitOnChild, m_WaitOnSync);
 
+	// if already has a base extension, switch places ... seems to be faster...
+	for (size_t n=0;n<m_InnerEngine->m_Eng_exts.size();++n)
+	{
+		Engine_Ext_CylinderMultiGrid* eng_mg = dynamic_cast<Engine_Ext_CylinderMultiGrid*>(m_InnerEngine->m_Eng_exts.at(n));
+		if (eng_mg)
+		{
+			m_InnerEngine->m_Eng_exts.at(n) = m_InnerEng_Ext_MG;
+			m_InnerEng_Ext_MG = eng_mg;
+			break;
+		}
+	}
 	m_InnerEngine->m_Eng_exts.push_back(m_InnerEng_Ext_MG);
 }
 
@@ -83,10 +95,10 @@ void Engine_CylinderMultiGrid::Init()
 
 	boost::thread *t = NULL;
 
-	t = new boost::thread( Engine_CylinderMultiGrid_Thread(this,m_startBarrier,m_stopBarrier,&m_Thread_NumTS) );
+	t = new boost::thread( Engine_CylinderMultiGrid_Thread(this,m_startBarrier,m_stopBarrier,&m_Thread_NumTS, true) );
 	m_IteratorThread_Group.add_thread( t );
 
-	t = new boost::thread( Engine_CylinderMultiGrid_Thread(m_InnerEngine,m_startBarrier,m_stopBarrier,&m_Thread_NumTS) );
+	t = new boost::thread( Engine_CylinderMultiGrid_Thread(m_InnerEngine,m_startBarrier,m_stopBarrier,&m_Thread_NumTS, false) );
 	m_IteratorThread_Group.add_thread( t );
 }
 
@@ -107,12 +119,6 @@ bool Engine_CylinderMultiGrid::IterateTS(unsigned int iterTS)
 	return true;
 }
 
-void Engine_CylinderMultiGrid::InitExtensions()
-{
-	m_InnerEngine->InitExtensions();
-	Engine_Multithread::InitExtensions();
-}
-
 void Engine_CylinderMultiGrid::InterpolVoltChild2Base(unsigned int rzPlane)
 {
 	//interpolate voltages from child engine to the base engine...
@@ -229,11 +235,12 @@ void Engine_CylinderMultiGrid::InterpolCurrChild2Base(unsigned int rzPlane)
 }
 
 /****************************************************************************************/
-Engine_CylinderMultiGrid_Thread::Engine_CylinderMultiGrid_Thread( Engine_Multithread* engine, boost::barrier *start, boost::barrier *stop, volatile unsigned int* numTS)
+Engine_CylinderMultiGrid_Thread::Engine_CylinderMultiGrid_Thread( Engine_Multithread* engine, boost::barrier *start, boost::barrier *stop, volatile unsigned int* numTS, bool isBase)
 {
 	m_startBarrier = start;
 	m_stopBarrier = stop;
 	m_Eng=engine;
+	m_isBase=isBase;
 	m_numTS = numTS;
 }
 
@@ -243,7 +250,10 @@ void Engine_CylinderMultiGrid_Thread::operator()()
 
 	while(*m_numTS>0)	//m_numTS==0 request to terminate this thread...
 	{
+		if (m_isBase)
 			m_Eng->Engine_Multithread::IterateTS(*m_numTS);
+		else
+			m_Eng->IterateTS(*m_numTS);
 		m_stopBarrier->wait();		//sync all workers after iterations are performed
 		m_startBarrier->wait();		//wait for Base engine to start the iterations again ...
 	}

FDTD/engine_cylindermultigrid.h

@@ -41,8 +41,6 @@ public:
 	//! Iterate \a iterTS number of timesteps
 	virtual bool IterateTS(unsigned int iterTS);
 
-	virtual void InitExtensions();
-
 protected:
 	Engine_CylinderMultiGrid(const Operator_CylinderMultiGrid* op);
 	const Operator_CylinderMultiGrid* Op_CMG;
@@ -62,18 +60,18 @@ protected:
 	boost::barrier *m_WaitOnSync;
 
 	Engine_Ext_CylinderMultiGrid* m_Eng_Ext_MG;
-	Engine_Ext_CylinderMultiGrid* m_InnerEng_Ext_MG;
 };
 
 
 class Engine_CylinderMultiGrid_Thread
 {
 public:
-	Engine_CylinderMultiGrid_Thread( Engine_Multithread* engine, boost::barrier *start, boost::barrier *stop, volatile unsigned int* numTS);
+	Engine_CylinderMultiGrid_Thread( Engine_Multithread* engine, boost::barrier *start, boost::barrier *stop, volatile unsigned int* numTS, bool isBase);
 	void operator()();
 
 protected:
 	Engine_Multithread *m_Eng;
+	bool m_isBase;
 	boost::barrier *m_startBarrier;
 	boost::barrier *m_stopBarrier;
 	volatile unsigned int *m_numTS;

FDTD/operator.cpp

@@ -36,6 +36,7 @@ Operator::Operator()
 	m_MeshType = ProcessFields::CARTESIAN_MESH;
 	Exc = 0;
 	dT = 0;
+	m_InvaildTimestep = false;
 }
 
 Operator::~Operator()
@@ -535,6 +536,7 @@ int Operator::CalcECOperator()
 	if (Calc_EC()==0)
 		return -1;
 
+	m_InvaildTimestep = false;
 	opt_dT = 0;
 	if (dT>0)
 	{
@@ -542,7 +544,11 @@ int Operator::CalcECOperator()
 		CalcTimestep();
 		opt_dT = dT;
 		if (dT<save_dT)
+		{
 			cerr << "Operator::CalcECOperator: Warning, forced timestep: " << save_dT << "s is larger than calculated timestep: " << dT << "s! It is not recommended using this timestep!! " << endl;
+			m_InvaildTimestep = true;
+		}
+
 		dT = save_dT;
 	}
 	else

FDTD/operator.h

@@ -60,6 +60,7 @@ public:
 	//! Set a forced timestep to use by the operator
 	virtual void SetTimestep(double ts) {dT = ts;}
 	double GetTimestep() const {return dT;};
+	bool GetTimestepValid() const {return !m_InvaildTimestep;}
 	virtual double GetNumberCells() const;
 
 	//! Returns the number of lines as needed for post-processing etc. (for the engine, use GetOriginalNumLines())
@@ -131,6 +132,7 @@ protected:
 	virtual double CalcTimestep();
 	double dT; //FDTD timestep!
 	double opt_dT;
+	bool m_InvaildTimestep;
 	string m_Used_TS_Name;
 
 	double CalcTimestep_Var1();

FDTD/operator_cylindermultigrid.cpp

@@ -21,8 +21,9 @@
 
 Operator_CylinderMultiGrid::Operator_CylinderMultiGrid(vector<double> Split_Radii) : Operator_Cylinder()
 {
-	m_Split_Rad = Split_Radii.back();
+	m_Split_Radii = Split_Radii;
-	Split_Radii.pop_back();
+	m_Split_Rad = m_Split_Radii.back();
+	m_Split_Radii.pop_back();
 }
 
 Operator_CylinderMultiGrid::~Operator_CylinderMultiGrid()
@@ -60,6 +61,18 @@ bool Operator_CylinderMultiGrid::SetGeometryCSX(ContinuousStructure* geo)
 	if (numLines[1]%2 != 1)
 	{
 		cerr << "Operator_CylinderMultiGrid::SetGeometryCSX: Error, number of line in alpha direction must be odd... found: " << numLines[1] << endl;
+		exit(0);
+	}
+
+	//check if mesh is homogenous in alpha-direction
+	double diff=discLines[1][1]-discLines[1][0];
+	for (unsigned int n=2;n<numLines[1];++n)
+	{
+		if ( fabs((discLines[1][n]-discLines[1][n-1]) - diff)/diff > 1e-10)
+		{
+			cerr << "Operator_CylinderMultiGrid::SetGeometryCSX: Error, mesh has to be homogenous in alpha direction for multi grid engine, violation found at: " << n << endl;
+			exit(0);
+		}
 	}
 
 	m_Split_Pos = 0;
@@ -105,7 +118,11 @@ bool Operator_CylinderMultiGrid::SetGeometryCSX(ContinuousStructure* geo)
 void Operator_CylinderMultiGrid::Init()
 {
 	Operator_Cylinder::Init();
+
+	if (m_Split_Radii.empty())
 		m_InnerOp = Operator_Cylinder::New(m_numThreads);
+	else
+		m_InnerOp = Operator_CylinderMultiGrid::New(m_Split_Radii,m_numThreads);
 }
 
 void Operator_CylinderMultiGrid::CalcStartStopLines(unsigned int &numThreads, vector<unsigned int> &start, vector<unsigned int> &stop) const
@@ -132,6 +149,7 @@ void Operator_CylinderMultiGrid::CalcStartStopLines(unsigned int &numThreads, ve
 
 int Operator_CylinderMultiGrid::CalcECOperator()
 {
+	int retCode=0;
 	if (dT)
 		m_InnerOp->SetTimestep(dT);
 
@@ -140,12 +158,22 @@ int Operator_CylinderMultiGrid::CalcECOperator()
 
 	dT = m_InnerOp->GetTimestep();
 
+	retCode = Operator_Cylinder::CalcECOperator();
+	if (GetTimestepValid()==false)
+	{
+		cerr << "Operator_CylinderMultiGrid::CalcECOperator(): Warning, timestep invalid... resetting..." << endl;
+		dT = opt_dT;
+		m_InnerOp->SetTimestep(dT);
+		m_InnerOp->CalcECOperator();
 		return Operator_Cylinder::CalcECOperator();
 	}
 
+	return retCode;
+}
+
 bool Operator_CylinderMultiGrid::SetupExcitation(TiXmlElement* Excite, unsigned int maxTS)
 {
-	if (!m_InnerOp->Exc->setupExcitation(Excite,maxTS))
+	if (!m_InnerOp->SetupExcitation(Excite,maxTS))
 		return false;
 	return Exc->setupExcitation(Excite,maxTS);
 }

FDTD/operator_cylindermultigrid.h

@@ -60,6 +60,7 @@ protected:
 	virtual void Reset();
 
 	double m_Split_Rad;
+	vector<double> m_Split_Radii;
 	unsigned int m_Split_Pos;
 
 	Operator_Cylinder* m_InnerOp;

matlab/examples/Coax_Cylindrical_MG.m

@@ -0,0 +1,155 @@
+close all
+clear
+clc
+
+%example for an cylindrical mesh, modeling a coaxial cable
+% this example is using a multi-grid approach
+
+
+%% setup %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Settings = [];
+Settings.LogFile = 'openEMS.log';
+
+physical_constants
+
+f0 = 0.5e9;
+epsR = 1;       %material filling
+
+length = 1000;
+port_dist = length/2;
+rad_i  = 10;    %inner radius
+rad_a = 200;    %outer radius
+partial = 0.5;  %e.g. 0.5 means only one half of a coax, should be <1 or change boundary cond.
+max_mesh = 10 / sqrt(epsR);
+max_alpha = max_mesh;
+N_alpha = ceil(rad_a * 2*pi * partial / max_alpha);
+
+%make it even...
+N_alpha = N_alpha + mod(N_alpha,2);
+%make sure it is multiple of 4, needed for 2 multi-grid steps
+N_alpha = ceil((N_alpha)/4) *4 + 1;
+
+openEMS_opts = '';
+% openEMS_opts = [openEMS_opts ' --disable-dumps'];
+% openEMS_opts = [openEMS_opts ' --debug-material'];
+% openEMS_opts = [openEMS_opts ' --numThreads=1'];
+
+def_refSimu = 0; % do a reference simulation without the multi-grid
+
+%% setup done %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+if (def_refSimu>0)
+    Sim_Path = 'tmp_ref';
+else
+    Sim_Path = 'tmp';
+end
+Sim_CSX = 'coax.xml';
+
+if (exist(Sim_Path,'dir'))
+    rmdir(Sim_Path,'s');
+end
+mkdir(Sim_Path);
+
+%setup FDTD parameter
+if (def_refSimu>0)
+    FDTD = InitCylindricalFDTD(1e5,1e-5,'OverSampling',5 );
+else
+    FDTD = InitCylindricalFDTD(1e5,1e-5,'OverSampling',5 ,'MultiGrid','60,120');
+end
+FDTD = SetGaussExcite(FDTD,f0,f0);
+BC = [0 0 1 1 2 2];
+FDTD = SetBoundaryCond(FDTD,BC);
+
+mesh_res = [max_mesh 2*pi*partial/N_alpha max_mesh];
+
+%setup CSXCAD geometry
+CSX = InitCSX();
+mesh.x = SmoothMeshLines([rad_i rad_a],mesh_res(1));
+mesh.y = linspace(-pi*partial,pi*partial,N_alpha);
+mesh.z = SmoothMeshLines([0 port_dist length],mesh_res(3));
+CSX = DefineRectGrid(CSX, 1e-3,mesh);
+
+start = [rad_i mesh.y(1)   mesh.z(3)];
+stop  = [rad_a mesh.y(end) mesh.z(3)];
+
+CSX = AddExcitation(CSX,'excite',0,[1 0 0]);
+weight{1} = '1/rho';
+weight{2} = 0;
+weight{3} = 0;
+CSX = SetExcitationWeight(CSX, 'excite', weight );
+CSX = AddBox(CSX,'excite',0 ,start,stop);
+ 
+
+start = [mesh.x(1)   mesh.y(1)   mesh.z(1)];
+stop  = [mesh.x(end) mesh.y(end) mesh.z(end)];
+CSX = AddMaterial(CSX,'material');
+CSX = SetMaterialProperty(CSX,'material','Epsilon',epsR);
+CSX = AddBox(CSX,'material',0 ,start,stop);
+
+%dump
+CSX = AddDump(CSX,'Et_rz_','DumpMode',0);
+start = [mesh.x(1)   0 mesh.z(1)];
+stop  = [mesh.x(end) 0 mesh.z(end)];
+CSX = AddBox(CSX,'Et_rz_',0 , start,stop);
+
+CSX = AddDump(CSX,'Ht_rz_','DumpType',1,'DumpMode',0);
+CSX = AddBox(CSX,'Ht_rz_',0 , start,stop);
+
+CSX = AddDump(CSX,'Et_','DumpType',0,'DumpMode',0);
+start = [mesh.x(1)   mesh.y(1)   length/2];
+stop  = [mesh.x(end) mesh.y(end) length/2];
+CSX = AddBox(CSX,'Et_',0,start,stop);
+
+CSX = AddDump(CSX,'Ht_','DumpType',1,'DumpMode',0);
+start = [mesh.x(1)   mesh.y(1)   length/2];
+stop  = [mesh.x(end) mesh.y(end) length/2];
+CSX = AddBox(CSX,'Ht_',0,start,stop);
+
+% voltage calc (take a voltage average to be at the same spot as the
+% current calculation)
+CSX = AddProbe(CSX,'ut1_1',0);
+start = [ rad_i 0 port_dist ];stop = [ rad_a 0 port_dist ];
+CSX = AddBox(CSX,'ut1_1', 0 ,start,stop);
+CSX = AddProbe(CSX,'ut1_2',0);
+start = [ rad_i 0 port_dist+mesh_res(3) ];stop = [ rad_a 0 port_dist+mesh_res(3) ];
+CSX = AddBox(CSX,'ut1_2', 0 ,start,stop);
+
+% current calc
+CSX = AddProbe(CSX,'it1',1);
+mid = 75;
+start = [ 0 mesh.y(1) port_dist+mesh_res(3)/2 ];stop = [ mid mesh.y(end) port_dist+mesh_res(3)/2 ];
+CSX = AddBox(CSX,'it1', 0 ,start,stop);
+
+%% Write openEMS compatoble xml-file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX);
+
+RunOpenEMS(Sim_Path, Sim_CSX, openEMS_opts, Settings)
+
+%%
+close all
+freq = linspace(0,2*f0,201);
+UI = ReadUI({'ut1_1','ut1_2','it1'},Sim_Path,freq);
+u_f = (UI.FD{1}.val + UI.FD{2}.val)/2;          %averaging voltages to fit current
+i_f = UI.FD{3}.val / partial;
+
+% plot(UI.TD{1}.t,UI.TD{1}.val);
+% grid on;
+% 
+% figure
+% plot(UI.TD{3}.t,UI.TD{3}.val);
+% grid on;
+
+%plot Z_L compare
+figure
+ZL = Z0/2/pi/sqrt(epsR)*log(rad_a/rad_i); %analytic line-impedance of a coax
+plot(UI.FD{1}.f,ZL*ones(size(u_f)),'g','Linewidth',3);
+hold on;
+grid on;
+Z = u_f./i_f;
+plot(UI.FD{1}.f,real(Z),'k--','Linewidth',2);
+plot(UI.FD{1}.f,imag(Z),'r-','Linewidth',2);
+xlim([0 2*f0]);
+legend('Z_L - analytic','\Re\{Z\} - FDTD','\Im\{Z\} - FDTD','Location','Best');
+
+