[ODE] biconjugate gradient

[Russ Smith]

i was reading the paper by Mendoza, Laugier, and Faure ... they appear
to make the claim that the biconjugate gradient method is better than
plain 'ol conjugate gradient for near singular rigid body systems.
i quote:

  "matrix sparsity allows the use of a biconjugate gradient algorithm
   [16], which iteratively refines a global solution even with singular
   matrices"

however: aren't the two methods equivalent when the matrix is symmetric?
(as J*inv(M)*J' definitely is). why is mendoza using BiCG when it has a
speed penalty but no advantage?

russ.

-- 
Russell Smith
http://www.q12.org