From: <domi@vi...>  20020327 13:26:31

vnl_sqrt doesnt solve Ax=b for systems aleardy around 30. For 20 it gives good results (for a naive linear problem) and: vnl_lsqr.cxx : x = 0 is the exact solution. No iterations were performed. vnl_lsqr.cxx : The iteration limit ITNLIM was reached. vnl_lsqr.cxx : residual norm estimate = 8.40484e06 vnl_lsqr.cxx : result norm estimate = 14.6304 vnl_lsqr.cxx : condition no. estimate = 67.683 vnl_lsqr.cxx : iterations = 20 whereas for 30 equations it goes banana (wrong solution): vnl_lsqr.cxx : x = 0 is the exact solution. No iterations were performed. vnl_lsqr.cxx : The iteration limit ITNLIM was reached. vnl_lsqr.cxx : residual norm estimate = 3.24731 vnl_lsqr.cxx : result norm estimate = 14.2702 vnl_lsqr.cxx : condition no. estimate = 106.047 vnl_lsqr.cxx : iterations = 30 I guess residual norm estimate holds the key. Any ideas? thanks Dominique 