1 files changed, 49 insertions, 0 deletions
diff --git a/src/c/signalProcessing/ifft/ir4tx.c b/src/c/signalProcessing/ifft/ir4tx.c
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+++ b/src/c/signalProcessing/ifft/ir4tx.c
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+/*
+ * Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
+ * Copyright (C) 2008 - INRIA - Allan SIMON
+ *
+ * This file must be used under the terms of the CeCILL.
+ * This source file is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.  The terms
+ * are also available at
+ * http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
+ *
+ */
+
+#include "ifft_internal.h"
+
+
+
+/*
+** radix 4 iteration subroutine
+*/
+/* this function do in one turn the same computation that do radix 2 in two turns  */
+void ir4tx( int nthpo, doubleComplex* c0, doubleComplex* c1, doubleComplex* c2, doubleComplex* c3)
+{
+  int kk;
+  doubleComplex temp1 , temp2 , temp3 , temp4 ;
+
+  for(kk=0;kk<nthpo;kk+=4)
+    {
+       /* real and imag parts alternate */
+
+    /* this first step is strictly equivalent than calling radix 2
+       except that radix would have needed 2 turns to compute what radix4 do in one */
+	temp1 = zadds ( c0[kk] , c2[kk] ) ;
+	temp2 = zdiffs( c0[kk] , c2[kk] ) ;
+	temp3 = zadds ( c1[kk] , c3[kk] ) ;
+	temp4 = zdiffs( c1[kk] , c3[kk] ) ;
+
+
+    /* strictly equivalent than calling radix2 with the temporary vector , but here also , radix4 do it in one turn
+    instead of two */
+	c0[kk] = zadds ( temp1 , temp3 );
+	c1[kk] = zdiffs( temp1 , temp3 );
+
+
+	c2[kk] = DoubleComplex ( zreals ( temp2 ) - zimags( temp4 ) , zimags ( temp2 ) + zreals( temp4 ) );
+	c3[kk] = DoubleComplex ( zreals ( temp2 ) + zimags( temp4 ) , zimags ( temp2 ) - zreals( temp4 ) );
+
+
+    }
+}