diff --git a/ProcessLib/HeatConduction/Tests.cmake b/ProcessLib/HeatConduction/Tests.cmake
index 12a31f6febe77c88bf200125171f2c6107a4ed85..dceab95729aae1e8e42f2e3ffe78bf074e4dd460 100644
--- a/ProcessLib/HeatConduction/Tests.cmake
+++ b/ProcessLib/HeatConduction/Tests.cmake
@@ -134,6 +134,129 @@ AddTest(
REQUIREMENTS NOT OGS_USE_MPI
)
+# a variation with a varying time step size
+AddTest(
+ NAME 1D_HeatConduction_dirichlet_varying_dt
+ PATH Parabolic/T/1D_dirichlet/varying_dt
+ EXECUTABLE ogs
+ EXECUTABLE_ARGS line_60_heat.xml
+ TESTER vtkdiff
+ DIFF_DATA
+ # numerical solution – ts 130
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ temperature temperature 4.6e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ heat_flux heat_flux 7.8e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ HeatFlowRate HeatFlowRate 7.5e-12 0
+ # numerical solution – ts 505
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ temperature temperature 9.4e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ heat_flux heat_flux 5.1e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ HeatFlowRate HeatFlowRate 5.5e-12 0
+ # numerical solution – ts 600
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ temperature temperature 1.3e-11 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ heat_flux heat_flux 6.4e-12 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ HeatFlowRate HeatFlowRate 6.4e-12 0
+ REQUIREMENTS NOT OGS_USE_MPI
+)
+
+# a variation with a varying time step size and <linear> optimization
+AddTest(
+ NAME 1D_HeatConduction_dirichlet_varying_dt_linear
+ PATH Parabolic/T/1D_dirichlet/varying_dt_linear
+ EXECUTABLE ogs
+ EXECUTABLE_ARGS line_60_heat.xml
+ TESTER vtkdiff
+ DIFF_DATA
+ # numerical solution – ts 130
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ temperature temperature 8e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ heat_flux heat_flux 8.3e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ HeatFlowRate HeatFlowRate 8.5e-12 0
+ # numerical solution – ts 505
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ temperature temperature 9.8e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ heat_flux heat_flux 5.0e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ HeatFlowRate HeatFlowRate 5.2e-12 0
+ # numerical solution – ts 600
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ temperature temperature 1.2e-11 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ heat_flux heat_flux 5.9e-12 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ HeatFlowRate HeatFlowRate 6.2e-12 0
+ REQUIREMENTS NOT OGS_USE_MPI
+)
+
+# a variation with a varying time step size and more optimizations
+AddTest(
+ NAME 1D_HeatConduction_dirichlet_varying_dt_linear_compute_only_on_dt_change
+ PATH Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change
+ EXECUTABLE ogs
+ EXECUTABLE_ARGS line_60_heat.xml
+ TESTER vtkdiff
+ DIFF_DATA
+ # numerical solution – ts 130
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ temperature temperature 8e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ heat_flux heat_flux 8.3e-13 0
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ line_60_heat_ts_130_t_5078125.000000.vtu
+ HeatFlowRate HeatFlowRate 8.5e-12 0
+ # numerical solution – ts 505
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ temperature temperature 9.8e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ heat_flux heat_flux 5.0e-12 0
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ line_60_heat_ts_505_t_31640625.000000.vtu
+ HeatFlowRate HeatFlowRate 5.2e-12 0
+ # numerical solution – ts 600
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ temperature temperature 1.2e-11 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ heat_flux heat_flux 5.9e-12 0
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ line_60_heat_ts_600_t_39062500.000000.vtu
+ HeatFlowRate HeatFlowRate 6.2e-12 0
+ REQUIREMENTS NOT OGS_USE_MPI
+)
+
AddTest(
NAME 1D_HeatConduction_neumann_picard
PATH Parabolic/T/1D_neumann
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.gml b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.gml
new file mode 120000
index 0000000000000000000000000000000000000000..c25e6617da567a81e61a6c8e9efc36c0d383edca
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.gml
@@ -0,0 +1 @@
+../line_60_heat.gml
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.pvd b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.pvd
new file mode 100644
index 0000000000000000000000000000000000000000..5b0cf36a1dd8f37f949f71f0d5d6556d93f4cac0
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.pvd
@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<VTKFile type="Collection" version="0.1" byte_order="LittleEndian" compressor="vtkZLibDataCompressor">
+ <Collection>
+ <DataSet timestep="0" group="" part="0" file="line_60_heat_ts_0_t_0.000000.vtu"/>
+ <DataSet timestep="5078125" group="" part="0" file="line_60_heat_ts_130_t_5078125.000000.vtu"/>
+ <DataSet timestep="7812500" group="" part="0" file="line_60_heat_ts_200_t_7812500.000000.vtu"/>
+ <DataSet timestep="31640625" group="" part="0" file="line_60_heat_ts_505_t_31640625.000000.vtu"/>
+ <DataSet timestep="39062500" group="" part="0" file="line_60_heat_ts_600_t_39062500.000000.vtu"/>
+ </Collection>
+</VTKFile>
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..99389beadeacf36fbb9f9b1a14d0707883aa3aac
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.vtu
@@ -0,0 +1 @@
+../line_60_heat.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.xml b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.xml
new file mode 100644
index 0000000000000000000000000000000000000000..bab27be155b5c592b1e51e21af2aecefad357c4c
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat.xml
@@ -0,0 +1,34 @@
+<?xml version='1.0' encoding='ISO-8859-1'?>
+<OpenGeoSysProjectDiff base_file="../line_60_heat.prj">
+ <remove sel="/*/time_loop/processes/process/time_stepping/timesteps"/>
+ <add sel="/*/time_loop/processes/process/time_stepping">
+ <timesteps>
+ <pair>
+ <repeat>200</repeat>
+ <delta_t>39062.5</delta_t>
+ </pair>
+ <pair>
+ <repeat>400</repeat>
+ <delta_t>78125</delta_t>
+ </pair>
+ </timesteps>
+ </add>
+
+ <remove sel="/*/time_loop/output/timesteps"/>
+ <add sel="/*/time_loop/output">
+ <timesteps>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 130 </each_steps>
+ </pair>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 70 </each_steps>
+ </pair>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 305 </each_steps>
+ </pair>
+ </timesteps>
+ </add>
+</OpenGeoSysProjectDiff>
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_0_t_0.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_0_t_0.000000.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..ef67d7b507fa3fba094a26be5e188ac62627886b
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_0_t_0.000000.vtu
@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<VTKFile type="UnstructuredGrid" version="1.0" byte_order="LittleEndian" header_type="UInt64" compressor="vtkZLibDataCompressor">
+ <UnstructuredGrid>
+ <FieldData>
+ <DataArray type="Int8" Name="OGS_VERSION" NumberOfTuples="25" format="appended" RangeMin="45" RangeMax="121" offset="0" />
+ </FieldData>
+ <Piece NumberOfPoints="61" NumberOfCells="60" >
+ <PointData>
+ <DataArray type="Float64" Name="HeatFlowRate" format="appended" RangeMin="0" RangeMax="0" offset="88" />
+ <DataArray type="Float64" Name="heat_flux" format="appended" RangeMin="-4.8521187068e-14" RangeMax="-4.8521187068e-14" offset="152" />
+ <DataArray type="Float64" Name="temperature" format="appended" RangeMin="273.15" RangeMax="273.15" offset="228" />
+ </PointData>
+ <CellData>
+ <DataArray type="Int32" Name="MaterialIDs" format="appended" RangeMin="0" RangeMax="0" offset="300" />
+ </CellData>
+ <Points>
+ <DataArray type="Float64" Name="Points" NumberOfComponents="3" format="appended" RangeMin="0" RangeMax="60" offset="360" />
+ </Points>
+ <Cells>
+ <DataArray type="Int64" Name="connectivity" format="appended" RangeMin="" RangeMax="" offset="612" />
+ <DataArray type="Int64" Name="offsets" format="appended" RangeMin="" RangeMax="" offset="808" />
+ <DataArray type="UInt8" Name="types" format="appended" RangeMin="" RangeMax="" offset="1012" />
+ </Cells>
+ </Piece>
+ </UnstructuredGrid>
+ <AppendedData encoding="base64">
+ _AQAAAAAAAAAAgAAAAAAAABkAAAAAAAAAIQAAAAAAAAA=eF4z0zPVM9A1NDbQTTdPNDAzN00x1kvJLCqpBABJiAaoAQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAADgAAAAAAAAA=eF5jYBgFIwEAAAHoAAE=AQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAAGAAAAAAAAAA=eF4rsOW6vjhAe2/BKD0s6UIoDQBx/9AHAQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAAEwAAAAAAAAA=eF5LSwMCoUKHtFF6WNMAs5Sn/g==AQAAAAAAAAAAgAAAAAAAAPAAAAAAAAAADAAAAAAAAAA=eF5jYBhZAAAA8AABAQAAAAAAAAAAgAAAAAAAALgFAAAAAAAAnAAAAAAAAAA=eF59yTkOAQAARNEplQqFQiEiIiJi3/d9P9Mc2REcwHy/fF/612cDY5u5AF4EL4GXwSvgVfAaeB28Ad4Eb4G3wTvgXfAeeB98AD4EH4GPwSfgU/AZ+Bx8Ab4EX4GvwTfg2+wG1y67wbXPbnAdshtcx+wG1ym7wXXObnBdshtc1+wG1y27wXXPbnA9shtcz+wG1yu7wfX+8S+zGCQEAQAAAAAAAAAAgAAAAAAAAMADAAAAAAAAcQAAAAAAAAA=eF5dxbMBAwAAALDatm3b/9/VoZ2SJYHAT5BDHOYIRznGcU5wklOc5gxnOcd5LnCRS1zmCle5xnVucJNb3OYOd7nHfR7wkEc85glPecZzXvCSV7zmDW95x3s+8JFPfOYLX/nGd37wk1/85s//L9CvDhE=AQAAAAAAAAAAgAAAAAAAAOABAAAAAAAAeAAAAAAAAAA=eF4txcEKQQEAADBJkiRJkiRJkiRJkvSSJEmSJEmSJEmSJJ/vYLssHPqLOOqY40446ZTTzjjrnPMuuOiSy6646prrbrjpltvuuOue+x448NAjjz3x1DPPvfDSK6+98dY7733w0SefffHVN9/98NMvv/3x1z8+Jw5NAQAAAAAAAAAAgAAAAAAAADwAAAAAAAAADAAAAAAAAAA=eF5jZiYfAAAVrgC1
+ </AppendedData>
+</VTKFile>
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_130_t_5078125.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_130_t_5078125.000000.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..0081cb8e49b6e92d418f61c7e6613c3e2050c2ef
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_130_t_5078125.000000.vtu
@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<VTKFile type="UnstructuredGrid" version="1.0" byte_order="LittleEndian" header_type="UInt64" compressor="vtkZLibDataCompressor">
+ <UnstructuredGrid>
+ <FieldData>
+ <DataArray type="Int8" Name="OGS_VERSION" NumberOfTuples="25" format="appended" RangeMin="45" RangeMax="121" offset="0" />
+ </FieldData>
+ <Piece NumberOfPoints="61" NumberOfCells="60" >
+ <PointData>
+ <DataArray type="Float64" Name="HeatFlowRate" format="appended" RangeMin="-3.1074402311e-12" RangeMax="0.7078753811" offset="88" />
+ <DataArray type="Float64" Name="heat_flux" format="appended" RangeMin="-6.679809621e-09" RangeMax="0.69908906127" offset="376" />
+ <DataArray type="Float64" Name="temperature" format="appended" RangeMin="273.15" RangeMax="274.15" offset="840" />
+ </PointData>
+ <CellData>
+ <DataArray type="Int32" Name="MaterialIDs" format="appended" RangeMin="0" RangeMax="0" offset="1140" />
+ </CellData>
+ <Points>
+ <DataArray type="Float64" Name="Points" NumberOfComponents="3" format="appended" RangeMin="0" RangeMax="60" offset="1200" />
+ </Points>
+ <Cells>
+ <DataArray type="Int64" Name="connectivity" format="appended" RangeMin="" RangeMax="" offset="1452" />
+ <DataArray type="Int64" Name="offsets" format="appended" RangeMin="" RangeMax="" offset="1648" />
+ <DataArray type="UInt8" Name="types" format="appended" RangeMin="" RangeMax="" offset="1852" />
+ </Cells>
+ </Piece>
+ </UnstructuredGrid>
+ <AppendedData encoding="base64">
+ _AQAAAAAAAAAAgAAAAAAAABkAAAAAAAAAIQAAAAAAAAA=eF4z0zPVM9A1NDbQTTdPNDAzN00x1kvJLCqpBABJiAaoAQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAAtgAAAAAAAAA=eF5jOJPn+mrZM3sGMEiwBZEODAF7QfSCVVV7IeINUH4WmE4ILQXTa1Y1gNUfWBUFphtCTaHqO2whdI0tWHoVWP+CVau6bCF0FlQ+YC+SupDQ0FAg/ef///+tQNonFMwH6l4FsncHiC6zZfgFlP6fvpchECRtujcGRIV2740C06F7w8BU895VYFAENT8Bal8ChXyYewOg/AwoPwNNfQaafAIB9cTaj86HAXRzYQCmPsAWAAPKYtU=AQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAAOwEAAAAAAAA=eF7bwPOE9UPcM/u6zQYbdvU9tRev9FA95fnYfqOHRHMxywN7vXeH5crW3LA/+fvNn2ezL9r/UNV/o+p03H7fiVVn3ybssV+n8ub9pFfr7cW8l/9UrV9g331/38WXNv32j7qP/Lr0rcp+wpPfJlvFU+3tJtmvkVzla78u3OjCki4j+6AfSfuZnUXsH1Wp3iy//snOjiv+i3TcGTv5Vu2w+cvm2e2Sa9XPS4myU2h97di+wWYf9/XFAberFfctKbDl2rr/5V6Rde4Pu0z32X7TiOl/dH2JbUz/oa8adYm2tlzXFxccdbJ9EbhDrlVbzPYJlKaULwq0r0rF3nY9kBLZZwG291Cuw96210AFpVZ7X6CpWwdV5wKk1rHL7sWlnlj70fk3FgMDIt4Hwx0wcZi91aCAMgvYCwBzWd4UAQAAAAAAAAAAgAAAAAAAAOgBAAAAAAAAvgAAAAAAAAA=eF5LSwMCpUKHI1VPJzyXK3TQC+c/s1K60EHuys7GBxKFDtPjv6WvECt0aGR17WcVLXSYcOse9wvhQodLE/1STID0k4tTnM4IFTqYPso/PwVIz/947VglkGab4304F0g/EZn8JgNIl/9+pJ0OpPOFPWenAenQ7ooiEC3QtTADROc+2JgGoh/qZ4Hp+/apYNpAIA1MH4mD0LPTIfSFNAidC6Uz0Oh0GvFhdBoB9Wlo4oTUk8vHZW4aGh8AGZ+0rw==AQAAAAAAAAAAgAAAAAAAAPAAAAAAAAAADAAAAAAAAAA=eF5jYBhZAAAA8AABAQAAAAAAAAAAgAAAAAAAALgFAAAAAAAAnAAAAAAAAAA=eF59yTkOAQAARNEplQqFQiEiIiJi3/d9P9Mc2REcwHy/fF/612cDY5u5AF4EL4GXwSvgVfAaeB28Ad4Eb4G3wTvgXfAeeB98AD4EH4GPwSfgU/AZ+Bx8Ab4EX4GvwTfg2+wG1y67wbXPbnAdshtcx+wG1ym7wXXObnBdshtc1+wG1y27wXXPbnA9shtcz+wG1yu7wfX+8S+zGCQEAQAAAAAAAAAAgAAAAAAAAMADAAAAAAAAcQAAAAAAAAA=eF5dxbMBAwAAALDatm3b/9/VoZ2SJYHAT5BDHOYIRznGcU5wklOc5gxnOcd5LnCRS1zmCle5xnVucJNb3OYOd7nHfR7wkEc85glPecZzXvCSV7zmDW95x3s+8JFPfOYLX/nGd37wk1/85s//L9CvDhE=AQAAAAAAAAAAgAAAAAAAAOABAAAAAAAAeAAAAAAAAAA=eF4txcEKQQEAADBJkiRJkiRJkiRJkvSSJEmSJEmSJEmSJJ/vYLssHPqLOOqY40446ZTTzjjrnPMuuOiSy6646prrbrjpltvuuOue+x448NAjjz3x1DPPvfDSK6+98dY7733w0SefffHVN9/98NMvv/3x1z8+Jw5NAQAAAAAAAAAAgAAAAAAAADwAAAAAAAAADAAAAAAAAAA=eF5jZiYfAAAVrgC1
+ </AppendedData>
+</VTKFile>
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_200_t_7812500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_200_t_7812500.000000.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..0e0fa720a9a024d547da22678de736ae0cb30a15
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_200_t_7812500.000000.vtu
@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<VTKFile type="UnstructuredGrid" version="1.0" byte_order="LittleEndian" header_type="UInt64" compressor="vtkZLibDataCompressor">
+ <UnstructuredGrid>
+ <FieldData>
+ <DataArray type="Int8" Name="OGS_VERSION" NumberOfTuples="25" format="appended" RangeMin="45" RangeMax="121" offset="0" />
+ </FieldData>
+ <Piece NumberOfPoints="61" NumberOfCells="60" >
+ <PointData>
+ <DataArray type="Float64" Name="HeatFlowRate" format="appended" RangeMin="-2.9558577808e-12" RangeMax="0.57078848908" offset="88" />
+ <DataArray type="Float64" Name="heat_flux" format="appended" RangeMin="-5.8806559622e-12" RangeMax="0.56613190966" offset="384" />
+ <DataArray type="Float64" Name="temperature" format="appended" RangeMin="273.15" RangeMax="274.15" offset="892" />
+ </PointData>
+ <CellData>
+ <DataArray type="Int32" Name="MaterialIDs" format="appended" RangeMin="0" RangeMax="0" offset="1232" />
+ </CellData>
+ <Points>
+ <DataArray type="Float64" Name="Points" NumberOfComponents="3" format="appended" RangeMin="0" RangeMax="60" offset="1292" />
+ </Points>
+ <Cells>
+ <DataArray type="Int64" Name="connectivity" format="appended" RangeMin="" RangeMax="" offset="1544" />
+ <DataArray type="Int64" Name="offsets" format="appended" RangeMin="" RangeMax="" offset="1740" />
+ <DataArray type="UInt8" Name="types" format="appended" RangeMin="" RangeMax="" offset="1944" />
+ </Cells>
+ </Piece>
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new file mode 100644
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+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_505_t_31640625.000000.vtu
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_600_t_39062500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_600_t_39062500.000000.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..284abd3b56b7349c7cfd581ac2ebb20c72f63015
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt/line_60_heat_ts_600_t_39062500.000000.vtu
@@ -0,0 +1,29 @@
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new file mode 120000
index 0000000000000000000000000000000000000000..c25e6617da567a81e61a6c8e9efc36c0d383edca
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.gml
@@ -0,0 +1 @@
+../line_60_heat.gml
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.pvd b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.pvd
new file mode 120000
index 0000000000000000000000000000000000000000..62834aa5c3828e55c23b29b571def12698815c3a
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.pvd
@@ -0,0 +1 @@
+../varying_dt/line_60_heat.pvd
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.vtu
new file mode 120000
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--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.vtu
@@ -0,0 +1 @@
+../line_60_heat.vtu
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.xml b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.xml
new file mode 100644
index 0000000000000000000000000000000000000000..4f356a5f27828ced3a529c7649145c9d08e9e91c
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat.xml
@@ -0,0 +1,38 @@
+<?xml version='1.0' encoding='ISO-8859-1'?>
+<OpenGeoSysProjectDiff base_file="../line_60_heat.prj">
+ <add sel="/*/processes/process">
+ <linear>true</linear>
+ </add>
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+ <remove sel="/*/time_loop/processes/process/time_stepping/timesteps"/>
+ <add sel="/*/time_loop/processes/process/time_stepping">
+ <timesteps>
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+ <repeat>200</repeat>
+ <delta_t>39062.5</delta_t>
+ </pair>
+ <pair>
+ <repeat>400</repeat>
+ <delta_t>78125</delta_t>
+ </pair>
+ </timesteps>
+ </add>
+
+ <remove sel="/*/time_loop/output/timesteps"/>
+ <add sel="/*/time_loop/output">
+ <timesteps>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 130 </each_steps>
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+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 70 </each_steps>
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+ <pair>
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+ <each_steps> 305 </each_steps>
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_0_t_0.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_0_t_0.000000.vtu
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_130_t_5078125.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_130_t_5078125.000000.vtu
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_200_t_7812500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_200_t_7812500.000000.vtu
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diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_505_t_31640625.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_505_t_31640625.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..7cafef93cd7488574c988ed90d76be991cd3e421
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_505_t_31640625.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_505_t_31640625.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_600_t_39062500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_600_t_39062500.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..ce92db3dd46e66f957be0dca0512198bf6af637c
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear/line_60_heat_ts_600_t_39062500.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_600_t_39062500.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.gml b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.gml
new file mode 120000
index 0000000000000000000000000000000000000000..c25e6617da567a81e61a6c8e9efc36c0d383edca
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.gml
@@ -0,0 +1 @@
+../line_60_heat.gml
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.pvd b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.pvd
new file mode 120000
index 0000000000000000000000000000000000000000..62834aa5c3828e55c23b29b571def12698815c3a
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.pvd
@@ -0,0 +1 @@
+../varying_dt/line_60_heat.pvd
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..99389beadeacf36fbb9f9b1a14d0707883aa3aac
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.vtu
@@ -0,0 +1 @@
+../line_60_heat.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.xml b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.xml
new file mode 100644
index 0000000000000000000000000000000000000000..e1ec26c894bdd60e53c14687fd77ad7a83129596
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat.xml
@@ -0,0 +1,39 @@
+<?xml version='1.0' encoding='ISO-8859-1'?>
+<OpenGeoSysProjectDiff base_file="../line_60_heat.prj">
+ <add sel="/*/processes/process">
+ <linear>true</linear>
+ <linear_solver_compute_only_upon_timestep_change>true</linear_solver_compute_only_upon_timestep_change>
+ </add>
+
+ <remove sel="/*/time_loop/processes/process/time_stepping/timesteps"/>
+ <add sel="/*/time_loop/processes/process/time_stepping">
+ <timesteps>
+ <pair>
+ <repeat>200</repeat>
+ <delta_t>39062.5</delta_t>
+ </pair>
+ <pair>
+ <repeat>400</repeat>
+ <delta_t>78125</delta_t>
+ </pair>
+ </timesteps>
+ </add>
+
+ <remove sel="/*/time_loop/output/timesteps"/>
+ <add sel="/*/time_loop/output">
+ <timesteps>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 130 </each_steps>
+ </pair>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 70 </each_steps>
+ </pair>
+ <pair>
+ <repeat> 1 </repeat>
+ <each_steps> 305 </each_steps>
+ </pair>
+ </timesteps>
+ </add>
+</OpenGeoSysProjectDiff>
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_0_t_0.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_0_t_0.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..3431dbadd15eb17d28fffcaefcf69be87041056b
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_0_t_0.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_0_t_0.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_130_t_5078125.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_130_t_5078125.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..83f84aee6b49d35ff2d1b7261c103ad077249b7e
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_130_t_5078125.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_130_t_5078125.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_200_t_7812500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_200_t_7812500.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..0244ac3e5a33dfdb04ac65beff5ee38ba2e8fbd8
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_200_t_7812500.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_200_t_7812500.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_505_t_31640625.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_505_t_31640625.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..7cafef93cd7488574c988ed90d76be991cd3e421
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_505_t_31640625.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_505_t_31640625.000000.vtu
\ No newline at end of file
diff --git a/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_600_t_39062500.000000.vtu b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_600_t_39062500.000000.vtu
new file mode 120000
index 0000000000000000000000000000000000000000..ce92db3dd46e66f957be0dca0512198bf6af637c
--- /dev/null
+++ b/Tests/Data/Parabolic/T/1D_dirichlet/varying_dt_linear_compute_only_on_dt_change/line_60_heat_ts_600_t_39062500.000000.vtu
@@ -0,0 +1 @@
+../varying_dt/line_60_heat_ts_600_t_39062500.000000.vtu
\ No newline at end of file