1 files changed, 116 insertions, 0 deletions
diff --git a/gsl-1.9/fft/real_pass_2.c b/gsl-1.9/fft/real_pass_2.c
new file mode 100644
index 0000000..b1f5184
--- /dev/null
+++ b/gsl-1.9/fft/real_pass_2.c
@@ -0,0 +1,116 @@
+/* fft/real_pass_2.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough
+ * 
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+static void
+FUNCTION(fft_real,pass_2) (const BASE in[],
+                           const size_t istride,
+                           BASE out[],
+                           const size_t ostride,
+                           const size_t product,
+                           const size_t n,
+                           const TYPE(gsl_complex) twiddle[])
+{
+  size_t k, k1;
+
+  const size_t factor = 2;
+  const size_t m = n / factor;
+  const size_t q = n / product;
+  const size_t product_1 = product / factor;
+
+  for (k1 = 0; k1 < q; k1++)
+    {
+      const size_t from0 = k1 * product_1;
+      const size_t from1 = from0 + m;
+
+      const ATOMIC r0 = VECTOR(in,istride,from0);
+      const ATOMIC r1 = VECTOR(in,istride,from1);
+      
+      const ATOMIC s0 = r0 + r1;
+      const ATOMIC s1 = r0 - r1;
+      
+      const size_t to0 = product * k1;
+      const size_t to1 = to0 + product - 1;
+      
+      VECTOR(out,ostride,to0) = s0;
+      VECTOR(out,ostride,to1) = s1;
+    }
+
+  if (product_1 == 1)
+    return;
+
+  for (k = 1; k < (product_1 + 1) / 2; k++)
+    {
+
+      /* forward real transform: w -> conjugate(w) */
+      const ATOMIC w_real = GSL_REAL(twiddle[k - 1]);
+      const ATOMIC w_imag = -GSL_IMAG(twiddle[k - 1]);
+
+      for (k1 = 0; k1 < q; k1++)
+        {
+          const size_t from0 = k1 * product_1 + 2 * k - 1;
+          const size_t from1 = from0 + m;
+
+          const ATOMIC f0_real = VECTOR(in,istride,from0);
+          const ATOMIC f0_imag = VECTOR(in,istride,from0 + 1);
+
+          const ATOMIC f1_real = VECTOR(in,istride,from1);
+          const ATOMIC f1_imag = VECTOR(in,istride,from1 + 1);
+
+          const ATOMIC z0_real = f0_real;
+          const ATOMIC z0_imag = f0_imag;
+
+          const ATOMIC z1_real = w_real * f1_real - w_imag * f1_imag;
+          const ATOMIC z1_imag = w_real * f1_imag + w_imag * f1_real;
+
+          /* compute x = W(2) z */
+
+          /* x0 = z0 + z1 */
+          const ATOMIC x0_real = z0_real + z1_real;
+          const ATOMIC x0_imag = z0_imag + z1_imag;
+
+          /* x1 = z0 - z1 */
+          const ATOMIC x1_real = z0_real - z1_real;
+          const ATOMIC x1_imag = z0_imag - z1_imag;
+
+          const size_t to0 = k1 * product + 2 * k - 1;
+          const size_t to1 = k1 * product + product - 2 * k - 1;
+          
+          VECTOR(out,ostride,to0) = x0_real;
+          VECTOR(out,ostride,to0 + 1) = x0_imag;
+          
+          /* stored in conjugate location */
+          VECTOR(out,ostride,to1) = x1_real;
+          VECTOR(out,ostride,to1 + 1) = -x1_imag;
+        }
+    }
+  
+  if (product_1 % 2 == 1)
+    return;
+
+  for (k1 = 0; k1 < q; k1++)
+    {
+      const size_t from0 = k1 * product_1 + product_1 - 1;
+      const size_t from1 = from0 + m;
+      const size_t to0 = k1 * product + product_1 - 1;
+
+      VECTOR(out,ostride,to0) = VECTOR(in,istride,from0);
+      VECTOR(out,ostride,to0 + 1) = -VECTOR(in,istride,from1);
+    }
+  return;
+}