Another output for QR factorization than in example

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Another output for QR factorization than in example

Postby Mat » Sun Aug 27, 2006 4:58 pm

Hello,

when i tried to implement the QR factorization example as described in the IBM Example: http://www.cepba.upc.edu/docs/ibm_doc/m ... sl368.html

i get another output for the Matrix R than they show on this page.
My code is:

Code: Select all
    double *A1,*work,*tau;
 
    A1 = (double*)calloc(12,sizeof(double));
       
    A1[0] = 0.0;
    A1[1] = 2.0;
    A1[2] = 2.0;
    A1[3] = 0.0;
    A1[4] = 2.0;
    A1[5] = 2.0;
    A1[6] = 2.0;
    A1[7] = -1.0;
    A1[8] = -1.0;
    A1[9] = 1.0;
    A1[10] = -1.0;
    A1[11] = -1.0;
   
   
    int m = 6;
    int n = 2;
    int lda = 6;
   
    work = (double*)calloc(2,sizeof(double));
    tau  = (double*)calloc(2,sizeof(double));
   
    int lwork = 2;
    int info;
       
   
    for(int i=0; i < 12; i++){
            printf("%f \n",A1[i]);         
    }
    printf("------------------------------------------------------------\n");
   
    dgeqrf_(&m,&n,A1,&m,tau,work,&n,&info);
   
   
    for(int i=0; i < 12; i++){
            printf("%f \n",A1[i]);
    }
    printf("------------------------------------------------------------\n");


And my output is:

Code: Select all
-4.0
0.5
0.5
0.0
0.5
0.5
2.0
2.236068
0.309017
-0.309017
0.309017
0.309017


Can anybody say where my problem is?
Mat
 
Posts: 47
Joined: Sat Aug 19, 2006 9:54 am

Postby Julie » Sun Aug 27, 2006 5:15 pm

Hello Mat,
what about setting A(4,2) (i.e. A1[9]) to 1.5 as in IBM ESSL example?
(You have set it to 1.0.)
Julie
Julie
 
Posts: 299
Joined: Wed Feb 23, 2005 12:32 am
Location: ICL, Denver. Colorado

Postby Mat » Mon Aug 28, 2006 12:08 pm

:oops:

sorry - after about 2 hours of checking if i really used the correct matrix A it seems i was blind yesterday evening. Thanks a lot.
The next time i will go to sleep if i can't see the forest because of the trees...*grmpf.

Thanks for your patient help again.
Mat
 
Posts: 47
Joined: Sat Aug 19, 2006 9:54 am


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