1 files changed, 98 insertions, 0 deletions
diff --git a/gsl-1.9/fft/c_pass_2.c b/gsl-1.9/fft/c_pass_2.c
new file mode 100644
index 0000000..b0dac46
--- /dev/null
+++ b/gsl-1.9/fft/c_pass_2.c
@@ -0,0 +1,98 @@
+/* fft/c_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 int
+FUNCTION(fft_complex,pass_2) (const BASE in[],
+                              const size_t istride,
+                              BASE out[],
+                              const size_t ostride,
+                              const gsl_fft_direction sign,
+                              const size_t product,
+                              const size_t n,
+                              const TYPE(gsl_complex) twiddle[])
+{
+  size_t i = 0, j = 0;
+  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;
+  const size_t jump = (factor - 1) * product_1;
+
+  for (k = 0; k < q; k++)
+    {
+      ATOMIC w_real, w_imag;
+
+      if (k == 0)
+        {
+          w_real = 1.0;
+          w_imag = 0.0;
+        }
+      else
+        {
+          if (sign == gsl_fft_forward)
+            {
+              /* forward tranform */
+              w_real = GSL_REAL(twiddle[k - 1]);
+              w_imag = GSL_IMAG(twiddle[k - 1]);
+            }
+          else
+            {
+              /* backward tranform: w -> conjugate(w) */
+              w_real = GSL_REAL(twiddle[k - 1]);
+              w_imag = -GSL_IMAG(twiddle[k - 1]);
+            }
+        }
+
+      for (k1 = 0; k1 < product_1; k1++)
+        {
+          const ATOMIC z0_real = REAL(in,istride,i);
+          const ATOMIC z0_imag = IMAG(in,istride,i);
+
+          const ATOMIC z1_real = REAL(in,istride,i+m);
+          const ATOMIC z1_imag = IMAG(in,istride,i+m);
+
+          /* 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;
+
+          /* apply twiddle factors */
+          
+          /* out0 = 1 * x0 */
+          REAL(out,ostride,j) = x0_real;
+          IMAG(out,ostride,j) = x0_imag;
+          
+          /* out1 = w * x1 */
+          REAL(out,ostride,j+product_1) = w_real * x1_real - w_imag * x1_imag;
+          IMAG(out,ostride,j+product_1) = w_real * x1_imag + w_imag * x1_real;
+          
+          i++;
+          j++;
+        }
+      j += jump;
+    }
+  return 0;
+}