Some examples of the difference in computation cost below. Tracing ratsimp
shows that it is doing very big and expensive algebraic calculations.
cf(2^(9/10)),cflength:3 => [1,1,6]
Evaluation took 84.57 seconds
cf(bfloat(2^(9/10))),fpprec:15 => [1,1,6,2,6,1,13,1,3,2,2,2,1,1,12,7]
Evaluation took 0.10 seconds
cf(2^(1/3)),cflength:1000;
Evaluation took 23.69 seconds
cf(bfloat(2^(1/3))),fpprec:1200 (gives 1200 terms)
Evaluation took 0.70 seconds