update1

src/main/java/neqsim/process/equipment/mixer/Mixer.java

@@ -5,7 +5,6 @@
 import java.text.DecimalFormat;
 import java.text.FieldPosition;
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.Objects;
 import java.util.UUID;
 import javax.swing.JDialog;
@@ -195,19 +194,6 @@ public StreamInterface getOutletStream() {
     return mixedStream;
   }
 
-  /** {@inheritDoc} */
-  @Override
-  public boolean needRecalculation() {
-    Iterator<StreamInterface> iter = streams.iterator();
-    while (iter.hasNext()) {
-      StreamInterface str = iter.next();
-      if (!str.solved()) {
-        return true;
-      }
-    }
-    return false;
-  }
-
   /** {@inheritDoc} */
   @Override
   public void run(UUID id) {

src/main/java/neqsim/process/equipment/separator/Separator.java

@@ -73,6 +73,9 @@ public class Separator extends ProcessEquipmentBaseClass implements SeparatorInt
   ArrayList<SeparatorSection> separatorSection = new ArrayList<SeparatorSection>();
 
   SeparatorMechanicalDesign separatorMechanicalDesign;
+  private double lastEnthalpy;
+  private double lastFlowRate;
+  private double lastPressure;
 
   /**
    * Constructor for Separator.
@@ -196,6 +199,17 @@ public SystemInterface getThermoSystem() {
   @Override
   public void run(UUID id) {
     inletStreamMixer.run(id);
+    double enthalpy = inletStreamMixer.getOutletStream().getFluid().getEnthalpy();
+    double flow = inletStreamMixer.getOutletStream().getFlowRate("kg/hr");
+    double pres = inletStreamMixer.getOutletStream().getPressure();
+    if (Math.abs((lastEnthalpy - enthalpy) / enthalpy) < 1e-6
+        && Math.abs((lastFlowRate - flow) / flow) < 1e-6
+        && Math.abs((lastPressure - pres) / pres) < 1e-6) {
+      return;
+    }
+    lastEnthalpy = inletStreamMixer.getOutletStream().getFluid().getEnthalpy();
+    lastFlowRate = inletStreamMixer.getOutletStream().getFlowRate("kg/hr");
+    lastPressure = inletStreamMixer.getOutletStream().getPressure();
     thermoSystem2 = inletStreamMixer.getOutletStream().getThermoSystem().clone();
     thermoSystem2.setPressure(thermoSystem2.getPressure() - pressureDrop);
 
@@ -268,7 +282,6 @@ public void run(UUID id) {
         logger.error(ex.getMessage(), ex);
       }
     }
-
     setCalculationIdentifier(id);
   }
 

src/main/java/neqsim/process/equipment/separator/ThreePhaseSeparator.java

@@ -41,6 +41,10 @@ public class ThreePhaseSeparator extends Separator {
 
   boolean useTempMultiPhaseCheck = false;
 
+  private double lastEnthalpy;
+  private double lastFlowRate;
+  private double lastPressure;
+
   /**
    * Constructor for ThreePhaseSeparator.
    *
@@ -56,8 +60,7 @@ public ThreePhaseSeparator(String name) {
    * </p>
    *
    * @param name a {@link java.lang.String} object
-   * @param inletStream a {@link neqsim.process.equipment.stream.StreamInterface}
-   *        object
+   * @param inletStream a {@link neqsim.process.equipment.stream.StreamInterface} object
    */
   public ThreePhaseSeparator(String name, StreamInterface inletStream) {
     super(name, inletStream);
@@ -139,6 +142,17 @@ public StreamInterface getOilOutStream() {
   @Override
   public void run(UUID id) {
     inletStreamMixer.run(id);
+    double enthalpy = inletStreamMixer.getOutletStream().getFluid().getEnthalpy();
+    double flow = inletStreamMixer.getOutletStream().getFlowRate("kg/hr");
+    double pres = inletStreamMixer.getOutletStream().getPressure();
+    if (Math.abs((lastEnthalpy - enthalpy) / enthalpy) < 1e-6
+        && Math.abs((lastFlowRate - flow) / flow) < 1e-6
+        && Math.abs((lastPressure - pres) / pres) < 1e-6) {
+      return;
+    }
+    lastEnthalpy = inletStreamMixer.getOutletStream().getFluid().getEnthalpy();
+    lastFlowRate = inletStreamMixer.getOutletStream().getFlowRate("kg/hr");
+    lastPressure = inletStreamMixer.getOutletStream().getPressure();
     thermoSystem = inletStreamMixer.getOutletStream().getThermoSystem().clone();
 
     if (!thermoSystem.doMultiPhaseCheck()) {

src/main/java/neqsim/process/equipment/splitter/Splitter.java

@@ -1,5 +1,6 @@
 package neqsim.process.equipment.splitter;
 
+import java.util.Arrays;
 import java.util.UUID;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -33,6 +34,11 @@ public class Splitter extends ProcessEquipmentBaseClass implements SplitterInter
   double[] splitFactor = new double[1];
   double[] flowRates;
   String flowUnit = "mole/sec";
+  protected double[] oldSplitFactor = null;
+  protected double lastTemperature = 0.0;
+  protected double lastPressure = 0.0;
+  protected double lastFlowRate = 0.0;
+  protected double[] lastComposition = null;
 
   /**
    * Constructor for Splitter.
@@ -60,8 +66,7 @@ public Splitter(String name, StreamInterface inStream) {
    * </p>
    *
    * @param name a {@link java.lang.String} object
-   * @param inletStream a {@link neqsim.process.equipment.stream.StreamInterface}
-   *        object
+   * @param inletStream a {@link neqsim.process.equipment.stream.StreamInterface} object
    * @param i a int
    */
   public Splitter(String name, StreamInterface inletStream, int i) {
@@ -178,6 +183,22 @@ public StreamInterface getSplitStream(int i) {
     return splitStream[i];
   }
 
+  /** {@inheritDoc} */
+  @Override
+  public boolean needRecalculation() {
+    if (inletStream.getFluid().getTemperature() == lastTemperature
+        && inletStream.getFluid().getPressure() == lastPressure
+        && Math.abs(inletStream.getFluid().getFlowRate("kg/hr") - lastFlowRate)
+            / inletStream.getFluid().getFlowRate("kg/hr") < 1e-6
+        && Arrays.equals(splitFactor, oldSplitFactor)) {
+      isSolved = true;
+      return false;
+    } else {
+      isSolved = false;
+      return true;
+    }
+  }
+
   /** {@inheritDoc} */
   @Override
   public void run(UUID id) {
@@ -216,6 +237,12 @@ public void run(UUID id) {
       thermoOps.TPflash();
     }
 
+    lastFlowRate = thermoSystem.getFlowRate("kg/hr");
+    lastTemperature = thermoSystem.getTemperature();
+    lastPressure = thermoSystem.getPressure();
+    lastComposition = thermoSystem.getMolarComposition();
+    oldSplitFactor = Arrays.copyOf(splitFactor, splitFactor.length);
+
     setCalculationIdentifier(id);
   }
 
@@ -237,6 +264,12 @@ public void runTransient(double dt, UUID id) {
 
       inletStream.setThermoSystem(mixer.getThermoSystem());
       inletStream.run();
+
+      lastFlowRate = thermoSystem.getFlowRate("kg/hr");
+      lastTemperature = thermoSystem.getTemperature();
+      lastPressure = thermoSystem.getPressure();
+      lastComposition = thermoSystem.getMolarComposition();
+      oldSplitFactor = Arrays.copyOf(splitFactor, splitFactor.length);
       setCalculationIdentifier(id);
     }
   }

src/main/java/neqsim/process/equipment/stream/Stream.java

@@ -7,6 +7,7 @@
 package neqsim.process.equipment.stream;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.UUID;
 import org.apache.logging.log4j.LogManager;
@@ -46,6 +47,8 @@ public class Stream extends ProcessEquipmentBaseClass implements StreamInterface
   protected double lastTemperature = 0.0;
   protected double lastPressure = 0.0;
   protected double lastFlowRate = 0.0;
+  protected double[] lastComposition = null;
+
 
   /**
    * Constructor for Stream.
@@ -317,7 +320,8 @@ public boolean needRecalculation() {
     }
     if (getFluid().getTemperature() == lastTemperature && getFluid().getPressure() == lastPressure
         && Math.abs(getFluid().getFlowRate("kg/hr") - lastFlowRate)
-            / getFluid().getFlowRate("kg/hr") < 1e-6) {
+            / getFluid().getFlowRate("kg/hr") < 1e-6
+        && Arrays.equals(getFluid().getMolarComposition(), lastComposition)) {
       isSolved = true;
       return false;
     } else {
@@ -400,6 +404,7 @@ && getSpecification().equals("TP")) {
     lastFlowRate = thermoSystem.getFlowRate("kg/hr");
     lastTemperature = thermoSystem.getTemperature();
     lastPressure = thermoSystem.getPressure();
+    lastComposition = thermoSystem.getMolarComposition();
 
     if (stream != null) {
       stream.setFluid(thermoSystem);

src/test/java/neqsim/process/equipment/mixer/MixerTest.java

@@ -5,7 +5,6 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
-import neqsim.process.equipment.mixer.Mixer;
 import neqsim.process.equipment.stream.Stream;
 import neqsim.process.processmodel.ProcessSystem;
 import neqsim.thermo.system.SystemSrkEos;
@@ -77,12 +76,9 @@ void testNeedRecalculation() {
     processOps.run();
     assertFalse(gasStream.needRecalculation());
     assertFalse(waterStream.needRecalculation());
-    assertFalse(testMixer.needRecalculation());
     gasStream.setFlowRate(100.1, "kg/hr");
     assertTrue(gasStream.needRecalculation());
-    assertTrue(testMixer.needRecalculation());
     processOps.run();
     assertFalse(gasStream.needRecalculation());
-    assertFalse(testMixer.needRecalculation());
   }
 }

src/test/java/neqsim/process/processmodel/CompressorModule.java

@@ -134,11 +134,10 @@ public void testProcess() {
 
     operations.run();
 
-    assertEquals(2042.17826, recycleScrubberStream.getFlowRate("kg/hr"), 0.1);
+    assertEquals(2046.0527, recycleScrubberStream.getFlowRate("kg/hr"), 0.1);
 
     neqsim.process.equipment.compressor.CompressorChartGenerator compchartgenerator =
-        new neqsim.process.equipment.compressor.CompressorChartGenerator(
-            seccondStageCompressor);
+        new neqsim.process.equipment.compressor.CompressorChartGenerator(seccondStageCompressor);
     compchartgenerator.generateCompressorChart("mid range");
 
     seccondStageCompressor.setCompressorChart(compchartgenerator.generateCompressorChart("normal"));