Use signed arithmetic in test data generator.

* This matches the array size type used in cdi.

tests/deco2d_model.c

@@ -43,16 +43,16 @@ modelRegionCompute(double region[], int nlev, int nlat, int nlon, const int chun
                    const double lons[], const double lats[], double mscale, double mrscale)
 {
   (void) nlev;
-  unsigned is = (unsigned) chunkStart[0], js = (unsigned) chunkStart[1], ks = (unsigned) chunkStart[2], m = (unsigned) chunkSize[0],
-           n = (unsigned) chunkSize[1], o = (unsigned) chunkSize[2], jstride = (unsigned) chunkSize[0],
-           kstride = ((jstride * (unsigned) chunkSize[1] + nproma - 1) / nproma) * nproma;
+  int is = chunkStart[0], js = chunkStart[1], ks = chunkStart[2], m = chunkSize[0], n = chunkSize[1], o = chunkSize[2],
+      jstride = chunkSize[0], kstride = ((jstride * chunkSize[1] + nproma - 1) / nproma) * nproma;
 
-  for (unsigned k = 0; k < o; ++k)
-    for (unsigned j = 0; j < n; ++j)
-      for (unsigned i = 0; i < m; ++i)
+  tsID %= nlon;
+  for (int k = 0; k < o; ++k)
+    for (int j = 0; j < n; ++j)
+      for (int i = 0; i < m; ++i)
         region[k * kstride + j * jstride + i]
-            = dg_wobble((lons[(i + is + (unsigned) tsID) % (unsigned) nlon] - lons[0]) / (lons[nlon - 1] - lons[0]),
-                        (lats[(j + js + k + ks) % (unsigned) nlat] - lats[0]) / (lats[nlat - 1] - lats[0]), mscale, mrscale);
+            = dg_wobble((lons[(i + is + tsID) % nlon] - lons[0]) / (lons[nlon - 1] - lons[0]),
+                        (lats[(j + js + k + ks) % nlat] - lats[0]) / (lats[nlat - 1] - lats[0]), mscale, mrscale);
 }
 
 #ifdef USE_MPI