1 files changed, 104 insertions, 0 deletions
diff --git a/gsl-1.9/fft/dft_source.c b/gsl-1.9/fft/dft_source.c
new file mode 100644
index 0000000..2f2c349
--- /dev/null
+++ b/gsl-1.9/fft/dft_source.c
@@ -0,0 +1,104 @@
+/* fft/dft_source.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.
+ */
+
+int
+FUNCTION(gsl_dft_complex,forward) (const BASE data[], 
+                                   const size_t stride, const size_t n,
+                                   BASE result[])
+{
+  gsl_fft_direction sign = gsl_fft_forward;
+  int status = FUNCTION(gsl_dft_complex,transform) (data, stride, n, result, sign);
+  return status;
+}
+
+int
+FUNCTION(gsl_dft_complex,backward) (const BASE data[], 
+                                    const size_t stride, const size_t n,
+                                    BASE result[])
+{
+  gsl_fft_direction sign = gsl_fft_backward;
+  int status = FUNCTION(gsl_dft_complex,transform) (data, stride, n, result, sign);
+  return status;
+}
+
+
+int
+FUNCTION(gsl_dft_complex,inverse) (const BASE data[], 
+                                   const size_t stride, const size_t n,
+                                   BASE result[])
+{
+  gsl_fft_direction sign = gsl_fft_backward;
+  int status = FUNCTION(gsl_dft_complex,transform) (data, stride, n, result, sign);
+
+  /* normalize inverse fft with 1/n */
+
+  {
+    const ATOMIC norm = ONE / (ATOMIC)n;
+    size_t i;
+    for (i = 0; i < n; i++)
+      {
+        REAL(result,stride,i) *= norm;
+        IMAG(result,stride,i) *= norm;
+      }
+  }
+  return status;
+}
+
+int
+FUNCTION(gsl_dft_complex,transform) (const BASE data[], 
+                                     const size_t stride, const size_t n,
+                                     BASE result[],
+                                     const gsl_fft_direction sign)
+{
+
+  size_t i, j, exponent;
+
+  const double d_theta = 2.0 * ((int) sign) * M_PI / (double) n;
+
+  /* FIXME: check that input length == output length and give error */
+
+  for (i = 0; i < n; i++)
+    {
+      ATOMIC sum_real = 0;
+      ATOMIC sum_imag = 0;
+
+      exponent = 0;
+
+      for (j = 0; j < n; j++)
+        {
+          double theta = d_theta * (double) exponent;
+          /* sum = exp(i theta) * data[j] */
+
+          ATOMIC w_real = (ATOMIC) cos (theta);
+          ATOMIC w_imag = (ATOMIC) sin (theta);
+
+          ATOMIC data_real = REAL(data,stride,j);
+          ATOMIC data_imag = IMAG(data,stride,j);
+
+          sum_real += w_real * data_real - w_imag * data_imag;
+          sum_imag += w_real * data_imag + w_imag * data_real;
+
+          exponent = (exponent + i) % n;
+        }
+      REAL(result,stride,i) = sum_real;
+      IMAG(result,stride,i) = sum_imag;
+    }
+
+  return 0;
+}