On entry: the type of error control. At each step in the numerical solution an estimate of the local error,
$\mathit{est}$, is made. For the current step to be accepted the following condition must be satisfied:
where
${\tau}_{r}$ and
${\tau}_{a}$ are defined by
RELABS | ${\tau}_{r}$ | ${\tau}_{a}$ |
'M' | TOL | 1.0 |
'A' | ${\epsilon}_{r}$ | ${\mathbf{TOL}}/{\epsilon}_{r}$ |
'R' | TOL | ${\epsilon}_{a}$ |
'D' | TOL | ${\epsilon}_{a}$ |
where
${\epsilon}_{r}$ and
${\epsilon}_{a}$ are small machine-dependent numbers and
${e}_{i}$ is an estimate of the local error at
${y}_{i}$, computed internally. If the condition is not satisfied, the step size is reduced and the solution is recomputed on the current step. If you wish to measure the error in the computed solution in terms of the number of correct decimal places, then
RELABS should be set to 'A' on entry, whereas if the error requirement is in terms of the number of correct significant digits, then
RELABS should be set to 'R'. If you prefer a mixed error test, then
RELABS should be set to 'M', otherwise if you have no preference,
RELABS should be set to the default 'D'. Note that in this case 'D' is taken to be 'R'.