Sstrange behavior MKL-FEAST

Sstrange behavior MKL-FEAST

 
At the moment I am trying to implement a minimal working example of the <<dfeast_scsrgv>>   routine  in c++ of the FEAST package to solve the generalized eigenvalue problem Ax=lBx. The problem size is just 4x4 for testing  purposes

The first time I executed the program I got the error:
Info =3 that is a warning  "Size of the subspace m0 is too small (m0<m)".

thus I changed the value of M0 from 4 to 10 and tried again.

This time I the error was  "201" which means  "Problem with size of initial subspace m0 (m0≤0)"

this does not make any sense as M0 is positive.
 

I would appreciate any help on this.


	#include <iostream>

	#include<math.h>

	#include<cmath>

	#include<algorithm>

	#include "mkl.h"

	#include "mkl_solvers_ee.h"

	using namespace std;

	///////TEST MATRIX///////////////

	/*
  A=        |1  0  0  1|

	        |0  2  1  0|

	        |0  1  3  0|

	        |1  0  0  4|

	 
 B=         |1  0  0  0|

	        |0  2  0  0|

	        |0  0  3  0|

	        |0  0  0  4|

	PROBLEM Ax=lBx
*/

	int main(){
  MKL_INT fpm[128];

	 

	 //MATRIX SET UP

	  double  AV[]={1,1,2,1,3,4};

	  MKL_INT IA[]={1,3,5,6,7};

	  MKL_INT JA[]={1,4,2,3,3,4};

	 

	  double  BV[]={1,2,3,4};

	  MKL_INT IB[]={1,2,3,4,5};

	  MKL_INT JB[]={1,2,3,4};

	//SET UP EIGENSOLVER

	//initialize parameters of FEAST algorithm

	feastinit(fpm);

	fpm[0]=1;

	char UPLO= 'U';                            //uses the upper triangular part of the matrix

	const MKL_INT N=4;                         //set problem size

	double Emin=double(0.0), Emax=double(4);   // bounds of the igenvalues to be searched

	MKL_INT M0=10;                              //initial guess

	MKL_INT M=N;

	MKL_INT info;                              //info of the outcome

	double epsout;                             //contains relative error

	MKL_INT loop;                              //ouput information

	double E[10];                               //will contain the eigenvalues

	double res[N];

	double X[4*4];                             //initial subspace guess

	 dfeast_scsrgv(&UPLO,&N,AV,IA,JA,BV,IB,JB,fpm,&epsout,&loop,&Emin,&Emax,&M0,E,X,&M,res,&info);

	 cout<<"INFO="<<info<<endl;

	  return 0;

	}

 

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Best Reply

hello,  

this is the problem with documentation -- the initial guess for subspace dimension have to be like the follows  0<M0<=n

regards, Gennady

the documentation would be updated the next update of MKL ( 11.1 update 2 ) - we will let you know when it will happens,

Thank you, that solved the problem

 

fyi -- the documentation has been updated into the version 11.1.2 released yesterday. You can check this update and let us know if any further issue/improvements we have to do with mkl's doc. regards, gennady. 

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