Retry LU decomposition if incremental mode fails (#1108)

* Retry LU decomposition if incremental mode fails Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * not recomputing der. They should not be destroyed by previous failed update Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * Add unit test checking the replay mechanism Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * complete coverage Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * hopefully fill coverage now Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * sonar picomanagement module does not like public tests - and some people apparently care about sonar stats of so called issues Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> * Add copyright and authorship on new file Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com> --------- Signed-off-by: Didier Vidal <didier.vidal_externe@rte-france.com>
powsybl · Nov 14, 2024 · d96584a · d96584a
1 parent c7da76f
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diff --git a/src/main/java/com/powsybl/openloadflow/equations/JacobianMatrix.java b/src/main/java/com/powsybl/openloadflow/equations/JacobianMatrix.java
@@ -12,6 +12,7 @@
 import com.powsybl.math.matrix.DenseMatrix;
 import com.powsybl.math.matrix.LUDecomposition;
 import com.powsybl.math.matrix.Matrix;
+import com.powsybl.math.matrix.MatrixException;
 import com.powsybl.math.matrix.MatrixFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -141,7 +142,18 @@ private void updateLu(boolean allowIncrementalUpdate) {
 
     private void updateValues(boolean allowIncrementalUpdate) {
         updateDer();
-        updateLu(allowIncrementalUpdate);
+        try {
+            updateLu(allowIncrementalUpdate);
+        } catch (MatrixException ex) {
+            if (allowIncrementalUpdate) {
+                // Try another time without incremental
+                LOGGER.warn("Exception when updating LU matrix in incremental mode. Retrying without incremental mode");
+                updateLu(false);
+            } else {
+                // Rethrow the exception
+                throw ex;
+            }
+        }
     }
 
     public void forceUpdate() {

diff --git a/src/test/java/com/powsybl/openloadflow/equations/LUDecompositionTest.java b/src/test/java/com/powsybl/openloadflow/equations/LUDecompositionTest.java
@@ -0,0 +1,143 @@
+/**
+ * Copyright (c) 2024, RTE (http://www.rte-france.com)
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+package com.powsybl.openloadflow.equations;
+
+import com.powsybl.iidm.network.test.EurostagTutorialExample1Factory;
+import com.powsybl.math.matrix.DenseMatrix;
+import com.powsybl.math.matrix.DenseMatrixFactory;
+import com.powsybl.math.matrix.LUDecomposition;
+import com.powsybl.math.matrix.MatrixException;
+import com.powsybl.openloadflow.ac.equations.AcEquationType;
+import com.powsybl.openloadflow.ac.equations.AcVariableType;
+import com.powsybl.openloadflow.network.FirstSlackBusSelector;
+import com.powsybl.openloadflow.network.LfBus;
+import com.powsybl.openloadflow.network.LfNetwork;
+import com.powsybl.openloadflow.network.impl.Networks;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * @author Didier Vidal {@literal <didier.vidal_externe at rte-france.com>}
+ */
+class LUDecompositionTest {
+
+    class LUDecompositionMockIncrementalFailure implements LUDecomposition {
+        private final LUDecomposition delegate;
+        private final SpyMatrixFactory spy;
+
+        public LUDecompositionMockIncrementalFailure(LUDecomposition delegate, SpyMatrixFactory spy) {
+            this.delegate = delegate;
+            this.spy = spy;
+        }
+
+        @Override
+        public void update() {
+            delegate.update();
+        }
+
+        @Override
+        public void solve(double[] b) {
+            delegate.solve(b);
+        }
+
+        @Override
+        public void solveTransposed(double[] b) {
+            delegate.solveTransposed(b);
+        }
+
+        @Override
+        public void solve(DenseMatrix b) {
+            delegate.solve(b);
+        }
+
+        @Override
+        public void solveTransposed(DenseMatrix b) {
+            delegate.solveTransposed(b);
+        }
+
+        @Override
+        public void close() {
+            delegate.close();
+        }
+
+        @Override
+        public void update(boolean allowIncrementalUpdate) {
+            if (allowIncrementalUpdate || spy.alwaysFail) {
+                spy.exceptionThrown = true;
+                throw new MatrixException("Sorry incremental update failed");
+            } else {
+                delegate.update(allowIncrementalUpdate);
+            }
+        }
+    }
+
+    class SpyMatrixFactory extends DenseMatrixFactory {
+        boolean exceptionThrown = false;
+        boolean alwaysFail = false;
+
+        @Override
+        public DenseMatrix create(int rowCount, int columnCount, int estimatedValueCount) {
+            return new DenseMatrix(rowCount, columnCount) {
+                @Override
+                public LUDecomposition decomposeLU() {
+                    return new LUDecompositionMockIncrementalFailure(super.decomposeLU(), SpyMatrixFactory.this);
+                }
+            };
+        }
+    }
+
+    @Test
+    void testIncrementalLURobustification() {
+
+        // The condition that cause an incremental LU decomposition to fail is hard to reproduce on small models.
+        // It has been seen in Security Analysis, on large models, when a contingence moves an AC emulation HVDC link above PMax
+        //
+        // This test uses a mocked DenseMatrix to reproduce the condition and check that the solve succeds
+
+        SpyMatrixFactory spyMatrixFactory = new SpyMatrixFactory();
+
+        List<LfNetwork> lfNetworks = Networks.load(EurostagTutorialExample1Factory.create(), new FirstSlackBusSelector());
+        LfNetwork network = lfNetworks.get(0);
+
+        LfBus bus = network.getBus(0);
+
+        EquationSystem<AcVariableType, AcEquationType> equationSystem = new EquationSystem<>();
+        equationSystem.createEquation(bus.getNum(), AcEquationType.BUS_TARGET_V).addTerm(equationSystem.getVariable(bus.getNum(), AcVariableType.BUS_V).createTerm())
+                .setActive(true);
+
+        double[] values = new double[] {0.1};
+
+        try (JacobianMatrix j = new JacobianMatrix(equationSystem, spyMatrixFactory)) {
+            // First update
+            j.solve(values);
+            assertFalse(spyMatrixFactory.exceptionThrown);
+            // second update that triggers incremental update
+            j.updateStatus(JacobianMatrix.Status.VALUES_INVALID);
+            j.solve(values);
+            // An eception should be thrown but the solve should continue
+            assertTrue(spyMatrixFactory.exceptionThrown);
+
+            // Force always fail
+            spyMatrixFactory.alwaysFail = true;
+            j.updateStatus(JacobianMatrix.Status.VALUES_INVALID);
+            assertThrows(MatrixException.class, () -> j.solve(values));
+
+            // Force always fail in non incremental case
+            spyMatrixFactory.alwaysFail = true;
+            j.updateStatus(JacobianMatrix.Status.VALUES_AND_ZEROS_INVALID);
+            assertThrows(MatrixException.class, () -> j.solve(values));
+        }
+
+    }
+}