[PATCH] Trying to avoid symptoms of == double comparison

[Wald Commits]

# HG changeset patch
# User gernotbelger
# Date 1520352257 -3600
# Node ID b10f8415798c9fdecbab1c53389e0c11a805a91a
# Parent  f972e1da4a633c69ba18a856a0c2892fa1b07151
Trying to avoid symptoms of == double comparison

diff -r f972e1da4a63 -r b10f8415798c artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhcalculation/DischargeValuesFinder.java
--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhcalculation/DischargeValuesFinder.java	Tue Mar 06 17:02:45 2018 +0100
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhcalculation/DischargeValuesFinder.java	Tue Mar 06 17:04:17 2018 +0100
@@ -17,12 +17,17 @@
 import org.dive4elements.river.artifacts.model.WQKms;
 import org.dive4elements.river.utils.DoubleUtil;
 
+import gnu.trove.TDoubleDoubleHashMap;
+
 /**
  * @author Gernot Belger
  */
 public final class DischargeValuesFinder {
 
     private final UnivariateRealFunction qInterpolator;
+
+    private final TDoubleDoubleHashMap exactValues;
+
     private final QKms qKms;
 
     /**
@@ -42,6 +47,14 @@
     public DischargeValuesFinder(final QKms qKms) {
         this.qKms = qKms;
         this.qInterpolator = qKms == null ? null : DoubleUtil.getLinearInterpolator(qKms.allKms(), qKms.allQs());
+
+        this.exactValues = new TDoubleDoubleHashMap(qKms.size());
+
+        for (int i = 0; i < qKms.size(); i++) {
+            final double station = qKms.getKm(i);
+            final double discharge = qKms.getQ(i);
+            this.exactValues.put(station, discharge);
+        }
     }
 
     /**
@@ -56,6 +69,13 @@
     }
 
     public double getDischarge(final double station) throws FunctionEvaluationException {
+
+        // IMPORTANT: we first try to retreive the exact value if it is present, to avoid rounding changes due to interpolation.
+        // This is important because in the WaterlevelExporter code, these values are double-compared (with '==' ...) in order
+        // to find the corresponding main-value.
+        if (this.exactValues.contains(station))
+            return this.exactValues.get(station);
+
         return this.qInterpolator.value(station);
     }
 }
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