rotmat.m

gmres.m为迭代算法GMRES的实现

function [ c, s ] = rotmat( a, b ) 

% 
% Compute the Givens rotation matrix parameters for a and b. 
% 
  if ( b == 0.0 ), 
      c = 1.0; 
      s = 0.0; 
  elseif ( abs(b) > abs(a) ), 
      temp = a / b; 
      s = 1.0 / sqrt( 1.0 + temp^2 ); 
      c = temp * s; 
  else 
      temp = b / a; 
      c = 1.0 / sqrt( 1.0 + temp^2 ); 
      s = temp * c; 
  end