From 277d1edfa17bf3719d90ddbac8e31f6181e952c3 Mon Sep 17 00:00:00 2001
From: Sandeep Gupta
Date: Sun, 18 Jun 2017 23:55:40 +0530
Subject: First commit

---
 src/c/linearAlgebra/hess/dhessa.c | 81 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 src/c/linearAlgebra/hess/dhessa.c

(limited to 'src/c/linearAlgebra/hess/dhessa.c')

diff --git a/src/c/linearAlgebra/hess/dhessa.c b/src/c/linearAlgebra/hess/dhessa.c
new file mode 100644
index 0000000..57f81b3
--- /dev/null
+++ b/src/c/linearAlgebra/hess/dhessa.c
@@ -0,0 +1,81 @@
+/* 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: Sandeep Gupta
+ Organization: FOSSEE, IIT Bombay
+ Email: toolbox@scilab.in
+ */
+
+/*This function finds the hessenberg form of a matrix A.*/
+
+#include "hess.h"
+#include <stdio.h>
+#include "string.h"
+#include "stdlib.h"
+#include "lapack.h"
+#include "matrixTranspose.h"
+#include "matrixMultiplication.h"
+
+extern int dgehrd_(int *, int *,int *,double *,int *,double *,double *,int *,int *);
+extern int dorghr_(int *, int *,int *,double *,int *,double *,double *,int *,int *);
+
+
+void dhessa(double *in1,int size,int nout,double *out1, double *out2){
+	int i,j,k;	
+	int N = size;
+	int ILO=1;
+	int IHI=N;
+	double *A;
+	int LDA=N;
+	double *TAU;
+	double *WORK;
+	int LWORK = N;
+	int INFO;
+	A = (double *)malloc((double)size*size*sizeof(double));
+	memcpy(A,in1,size*size*sizeof(double));
+	TAU = (double *)malloc((double)size*sizeof(double));
+	WORK = (double *)malloc((double)LWORK*sizeof(double));
+	dgehrd_(&N,&ILO,&IHI,A,&LDA,TAU,WORK,&N,&INFO);
+		
+	for(i=0;i<N;i++)
+		for(j=0;j<N;j++)
+			out2[i+j*N] = A[i+j*N];
+	
+	for(j=1;j<=N-2;j++){
+		for(i=j+2;i<=N;i++){
+			out2[(i-1)+(j-1)*N] = 0;
+		}
+	}
+	
+	if(nout > 1){
+		dorghr_(&N,&ILO,&IHI,A,&LDA,TAU,WORK,&LWORK,&INFO);
+		for(i=0;i<N;i++)
+			for(j=0;j<N;j++)
+				out1[i+j*N] = A[i+j*N];
+	}
+	
+	/*for(i=0;i<N;i++){
+		 for(j=0;j<N;j++){
+			if(i == j) out1[i+j*N]=1;			
+			else out1[i+j*N]=0;		
+		} 
+	}
+	double result[size*size];
+	for(i=IHI-2;i>=ILO-1;i--){
+		tau = TAU[i];
+		double V[size],v[size],v1[size*size];		
+		for(j=0;j<i;j++) V[j]=0;
+		V[j]=1*tau;
+		for(j=i+1;j<IHI;j++) V[j] = tau*A[j+i*N];	
+		dtransposea (V,N,1,v);
+		dmulma(V,N,1,v,1,N,v1);		
+		for(j=0;j<N;j++) for(k=0;k<N;k++) if(j == k) v1[j+k*N]--;
+		for(j=0;j<N;j++) for(k=0;k<N;k++) result[j+k*N] = out1[j+k*N];
+		dmulma(v1,N,N,result,N,N,out1);
+	}*/	
+	//out2 = NULL;
+}
-- 
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