Heuristic: do not use t2 simd codelets for N>1024.

dft/simd/Makefile.am

@@ -1,5 +1,5 @@
 AM_CPPFLAGS = -I$(top_srcdir)/kernel -I$(top_srcdir)/dft -I$(top_srcdir)/simd
 noinst_LTLIBRARIES = libdft_simd.la
 SUBDIRS = codelets
-libdft_simd_la_SOURCES = n1b.c n1f.c n2b.c n2f.c q1b.c q1f.c t1b.c	\
-t1f.c n1b.h n1f.h n2b.h n2f.h q1b.h q1f.h t1b.h t1f.h t2b.h t2f.h
+libdft_simd_la_SOURCES = n1b.c n1f.c n2b.c n2f.c q1b.c q1f.c t.c n1b.h	\
+n1f.h n2b.h n2f.h q1b.h q1f.h t1b.h t1f.h t2b.h t2f.h

dft/simd/t.c

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2003 Matteo Frigo
+ * Copyright (c) 2003 Massachusetts Institute of Technology
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+
+#include "codelet-dft.h"
+
+#if HAVE_SIMD
+
+#include "simd.h"
+
+static int okp_common(const ct_desc *d,
+		      const R *rio, const R *iio, 
+		      int ios, int vs, int m, int dist, 
+		      const planner *plnr)
+{
+     UNUSED(rio);
+     UNUSED(iio);
+     return (RIGHT_CPU()
+	     && !NO_SIMDP(plnr)
+	     && SIMD_STRIDE_OKA(ios)
+	     && SIMD_VSTRIDE_OKA(dist)
+             && (m % VL) == 0
+	     && (!d->s1 || (d->s1 == ios))
+	     && (!d->s2 || (d->s2 == vs))
+	     && (!d->dist || (d->dist == dist))
+	  );
+}
+
+static int okp_t1f(const ct_desc *d,
+		   const R *rio, const R *iio, 
+		   int ios, int vs, int m, int dist, 
+		   const planner *plnr)
+{
+     return  okp_common(d, rio, iio, ios, vs, m, dist, plnr)
+	  && iio == rio + 1
+	  && ALIGNEDA(rio);
+}
+
+const ct_genus X(dft_t1fsimd_genus) = { okp_t1f, VL };
+
+static int okp_t1b(const ct_desc *d,
+		   const R *rio, const R *iio, 
+		   int ios, int vs, int m, int dist, 
+		   const planner *plnr)
+{
+     return  okp_common(d, rio, iio, ios, vs, m, dist, plnr)
+	  && rio == iio + 1
+	  && ALIGNEDA(iio);
+}
+
+const ct_genus X(dft_t1bsimd_genus) = { okp_t1b, VL };
+
+/* use t2* codelets only when n = m*radix is small, because
+   t2* codelets use ~2n twiddle factors (instead of ~n) */
+static int small_enough(const ct_desc *d, int m)
+{
+     return m * d->radix <= 1024;
+}
+
+static int okp_t2f(const ct_desc *d,
+		   const R *rio, const R *iio, 
+		   int ios, int vs, int m, int dist, 
+		   const planner *plnr)
+{
+     return  okp_t1f(d, rio, iio, ios, vs, m, dist, plnr)
+	  && small_enough(d, m);
+}
+
+const ct_genus X(dft_t2fsimd_genus) = { okp_t2f, VL };
+
+static int okp_t2b(const ct_desc *d,
+		   const R *rio, const R *iio, 
+		   int ios, int vs, int m, int dist, 
+		   const planner *plnr)
+{
+     return  okp_t1b(d, rio, iio, ios, vs, m, dist, plnr)
+	  && small_enough(d, m);
+}
+
+const ct_genus X(dft_t2bsimd_genus) = { okp_t2b, VL };
+
+#endif /* HAVE_SIMD */

dft/simd/t2b.h

@@ -30,7 +30,6 @@
 #define BYTW BYTW2
 #define BYTWJ BYTWJ2
 
-/* genus is the same as t1b */
-#define GENUS X(dft_t1bsimd_genus)
+#define GENUS X(dft_t2bsimd_genus)
 extern const ct_genus GENUS;
 

dft/simd/t2f.h

@@ -30,7 +30,6 @@
 #define BYTW BYTW2
 #define BYTWJ BYTWJ2
 
-/* genus is the same as t1f */
-#define GENUS X(dft_t1fsimd_genus)
+#define GENUS X(dft_t2fsimd_genus)
 extern const ct_genus GENUS;