# HG changeset patch
# User Sascha L. Teichmann <sascha.teichmann@intevation.de>
# Date 1346834292 0
# Node ID 171db4d5d3cbeeaedc5042f458255372afc0d18e
# Parent  83c0735092a39013dc699aae471a14c45df04d1c
FixA: AT export: prevent some numerical problems with steep functions around zero.

flys-artifacts/trunk@5363 c6561f87-3c4e-4783-a992-168aeb5c3f6f

diff -r 83c0735092a3 -r 171db4d5d3cb flys-artifacts/ChangeLog
--- a/flys-artifacts/ChangeLog	Wed Sep 05 08:23:56 2012 +0000
+++ b/flys-artifacts/ChangeLog	Wed Sep 05 08:38:12 2012 +0000
@@ -1,3 +1,9 @@
+2012-09-05	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
+
+	* src/main/java/de/intevation/flys/exports/fixings/FixATWriter.java:
+	  Only goto down to Q = 0.0001 to circumvent some numerial issues
+	  with steep functions around zero.
+
 2012-09-05	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
 
 	* src/main/java/de/intevation/flys/exports/fixings/FixATWriter.java:
diff -r 83c0735092a3 -r 171db4d5d3cb flys-artifacts/src/main/java/de/intevation/flys/exports/fixings/FixATWriter.java
--- a/flys-artifacts/src/main/java/de/intevation/flys/exports/fixings/FixATWriter.java	Wed Sep 05 08:23:56 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/exports/fixings/FixATWriter.java	Wed Sep 05 08:38:12 2012 +0000
@@ -32,6 +32,7 @@
 
     private static final int    MAX_ITERATIONS = 10000;
     private static final double EPSILON        = 1e-8;
+    private static final double MIN_Q          = 1e-4;
 
     protected Function   function;
     protected Parameters parameters;
@@ -166,7 +167,7 @@
             double w = lastW - stepWidth;
             double q = function.value(w);
 
-            if (Double.isNaN(q) || q > lastQ || q < 0d) {
+            if (Double.isNaN(q) || q > lastQ || q < MIN_Q) {
                 if (stepWidth < EPSILON) {
                     break;
                 }