1 files changed, 126 insertions, 0 deletions
diff --git a/2.3-1/src/c/linearAlgebra/schur/dschura.c b/2.3-1/src/c/linearAlgebra/schur/dschura.c
new file mode 100644
index 00000000..802caa81
--- /dev/null
+++ b/2.3-1/src/c/linearAlgebra/schur/dschura.c
@@ -0,0 +1,126 @@
+/* Copyright (C) 2017 - IIT Bombay - FOSSEE
+
+ 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
+ Author: Siddhesh Wani
+ Organization: FOSSEE, IIT Bombay
+ Email: toolbox@scilab.in
+ */
+
+/*Funtion to find schur decomposition of given square matrix */
+#include "schur.h"
+#include "lapack.h"
+#include "stdlib.h"
+#include "string.h"
+#include <math.h>
+
+/*flag  --> 0: nothing
+		--> 1: continuous
+		--> 2: discrete
+*/
+
+lapack_logical selctg11( double* in1, double* in2);
+lapack_logical selctg12( double* in1, double* in2);
+
+double dschura(double* in1, int size, int flag, int nout, double* out1, \
+		double* out2)
+{
+	char JOBVS = 'N';
+	char SORT = 'N';
+	int SDIM = 0;
+	int LVDS = size;
+    int LWORK = 3*size, INFO;
+	double *WR, *WI, *VS, *WORK;
+	int *BWORK;
+	double ret = 0;
+	double *buf; /*input is copied to buf, since lapack function direclty
+	modifies the input variable*/
+
+
+	/*Used incase of flag > 0*/
+	LAPACK_D_SELECT2 selctg;
+
+	if(flag == 1 || flag == 0) 
+		selctg = &selctg11;
+	else if(flag == 2)	  
+		selctg = &selctg12;
+	
+	if(nout >= 2) JOBVS = 'V';
+	if(flag > 0) SORT = 'S';
+
+	buf = (double*) malloc((double) size*size*sizeof(double));
+	WR = (double*) malloc((double) size*sizeof(double));
+	WI = (double*) malloc((double) size*sizeof(double));
+	VS = (double*) malloc((double) LVDS*size*sizeof(double));
+	WORK = (double*) malloc((double) LWORK*sizeof(double));
+	BWORK = (int*) malloc((double) size*sizeof(double));
+
+
+	memcpy(buf,in1,size*size*sizeof(double));
+
+	dgees_(&JOBVS,&SORT,selctg,&size,buf,&size,&SDIM,WR,WI,VS,&LVDS, \
+		WORK,&LWORK,BWORK,&INFO);
+
+	/*if (INFO != 0)
+	{
+		out1 = NULL;
+		return 0;	
+	} */
+
+	if(nout == 1)
+	{
+		/*Copy result in in1 to out1*/
+		memcpy(out1,buf,size*size*sizeof(double));
+	}
+	else if(nout == 2)
+	{
+		if(flag == 0)
+		{
+			/*copy in1 to out2 and VS to out1*/
+			memcpy(out2,buf,size*size*sizeof(double));
+			memcpy(out1,VS,size*size*sizeof(double));
+		}
+		else
+		{
+			/*copy VS to out1 and SDIM to out2*/
+			memcpy(out1,VS,size*size*sizeof(double));
+			ret = SDIM;
+		}
+	}
+	else 
+	{
+		/*copy VS to out1, SDIM to out2, in1 to out3*/
+		memcpy(out1,VS,size*size*sizeof(double));
+		memcpy(out2,buf,size*size*sizeof(double));
+		ret = SDIM;
+	}
+
+	free(buf);
+	free(WI);
+	free(WR);
+	free(VS);
+	free(WORK);
+	free(BWORK);
+
+	return ret;
+}
+
+lapack_logical selctg11(double* in1, double* in2)
+{
+	if(*in1 <= 0)
+		return 1;
+	else 
+		return 0;
+}
+
+lapack_logical selctg12(double* in1, double* in2)
+{
+
+	if(sqrt(*in1**in1+*in2**in2) < 1)
+		return 1;
+	else 
+		return 0;
+}
+\ No newline at end of file