From d213198312bce97abc76d50828ae11d1e1049948 Mon Sep 17 00:00:00 2001
From: rhaas <rhaas@df1f8a13-aa1d-4dd4-9681-27ded5b42416>
Date: Wed, 19 Jun 2013 03:34:21 +0000
Subject: add 0th order interpolation

minor extra changes:
 * correct typo
 * turn if-else cascade into switch


git-svn-id: http://svn.cactuscode.org/arrangements/CactusNumerical/LocalInterp/trunk@221 df1f8a13-aa1d-4dd4-9681-27ded5b42416
---
 src/Interpolate.c | 86 +++++++++++++++++++++++++++++++------------------------
 1 file changed, 48 insertions(+), 38 deletions(-)

diff --git a/src/Interpolate.c b/src/Interpolate.c
index 56df7d0..06503ba 100644
--- a/src/Interpolate.c
+++ b/src/Interpolate.c
@@ -305,9 +305,9 @@ int LocalInterp_Interpolate (int order,
     return UTIL_ERROR_BAD_INPUT;
   }
 
-  if (order < 1)
+  if (order < 0)
   {
-    CCTK_WARN (1, "Inperpolation order must be positive");
+    CCTK_WARN (1, "Interpolation order must be non-negative");
     return UTIL_ERROR_BAD_INPUT;
   }
 
@@ -511,44 +511,54 @@ if (n == LocalInterp_verbose_debug_n)
      * NOTE-MAXORDER: support higher interpolation orders by adding the
      *                appropriate coefficients in another else branch
      */
-    if (order == 1)
-    {
-      /* first order (linear) 1D interpolation */
-      for (int i = 0; i < num_dims; i++)
-      {
-        coeff[i][0] = 1 - offset[i];
-        coeff[i][1] =     offset[i];
-      }
-    }
-    else if (order == 2)
-    {
-      /* second order (quadratic) 1D interpolation */
-      for (int i = 0; i < num_dims; i++)
-      {
-        coeff[i][0] = (1-offset[i]) * (2-offset[i]) / (  2  *   1 );
-        coeff[i][1] = ( -offset[i]) * (2-offset[i]) / (  1  * (-1));
-        coeff[i][2] = ( -offset[i]) * (1-offset[i]) / ((-1) * (-2));
-      }
-    }
-    else if (order == 3)
-    {
-      /* third order (cubic) 1D interpolation */
-      for (int i = 0; i < num_dims; i++)
-      {
-        coeff[i][0] = (1-offset[i]) * (2-offset[i]) * (3-offset[i]) /
-                      (  3  *   2  *   1 );
-        coeff[i][1] = ( -offset[i]) * (2-offset[i]) * (3-offset[i]) /
-                      (  2  *   1  * (-1));
-        coeff[i][2] = ( -offset[i]) * (1-offset[i]) * (3-offset[i]) /
-                      (  1  * (-1) * (-2));
-        coeff[i][3] = ( -offset[i]) * (1-offset[i]) * (2-offset[i]) /
-                      ((-1) * (-2) * (-3));
-      }
-    }
-    else
+    switch(order)
     {
+      case 0:
+        /* zeroeth order (copy) 1D interpolation */
+        for (int i = 0; i < num_dims; i++)
+        {
+          coeff[i][0] = 1;
+        }
+        break;
+      case 1:
+        /* first order (linear) 1D interpolation */
+        for (int i = 0; i < num_dims; i++)
+        {
+          coeff[i][0] = 1 - offset[i];
+          coeff[i][1] =     offset[i];
+        }
+        break;
+      case 2:
+        /* second order (quadratic) 1D interpolation */
+        for (int i = 0; i < num_dims; i++)
+        {
+          coeff[i][0] = (1-offset[i]) * (2-offset[i]) / (  2  *   1 );
+          coeff[i][1] = ( -offset[i]) * (2-offset[i]) / (  1  * (-1));
+          coeff[i][2] = ( -offset[i]) * (1-offset[i]) / ((-1) * (-2));
+        }
+        break;
+      case 3:
+        /* third order (cubic) 1D interpolation */
+        for (int i = 0; i < num_dims; i++)
+        {
+          coeff[i][0] = (1-offset[i]) * (2-offset[i]) * (3-offset[i]) /
+                        (  3  *   2  *   1 );
+          coeff[i][1] = ( -offset[i]) * (2-offset[i]) * (3-offset[i]) /
+                        (  2  *   1  * (-1));
+          coeff[i][2] = ( -offset[i]) * (1-offset[i]) * (3-offset[i]) /
+                        (  1  * (-1) * (-2));
+          coeff[i][3] = ( -offset[i]) * (1-offset[i]) * (2-offset[i]) /
+                        ((-1) * (-2) * (-3));
+        }
+        break;
+      default:
 #pragma omp critical
-      CCTK_WARN (0, "Implementation error");
+        {
+        CCTK_VError (__LINE__,__FILE__,CCTK_THORNSTRING,
+                     "Implementation error. Unexpected interpolation order %d",
+                     order);
+        }
+        break;
     }
 
 #ifdef LOCALINTERP_VERBOSE_DEBUG
-- 
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