### culaSyvex ifail and abstol

Posted:

**Wed Nov 03, 2010 8:49 am**Hi admin,

according to the cula reference, the culaSyvex(double or single) api get ifail and abstol 2 special parametres, the abstol value is recommended to 2x machine epsilon which for double is 2.2204e-016 and for single is 1.1921e-007 in my PC. the ifail parametre indicate the indice of eigenvalue , where there is a culaNoError returned or not, 0 means no error and the Eigenvector converge.

my question is i tried many matrix and never get 0 in the ifail. i tried abstol=0 or 2.2204e-016, each one never got 0 in ifail, so what does the values in the ifail mean exactely. need some explanations plz.

according to the cula reference, the culaSyvex(double or single) api get ifail and abstol 2 special parametres, the abstol value is recommended to 2x machine epsilon which for double is 2.2204e-016 and for single is 1.1921e-007 in my PC. the ifail parametre indicate the indice of eigenvalue , where there is a culaNoError returned or not, 0 means no error and the Eigenvector converge.

my question is i tried many matrix and never get 0 in the ifail. i tried abstol=0 or 2.2204e-016, each one never got 0 in ifail, so what does the values in the ifail mean exactely. need some explanations plz.