Number Taylor Coefficient Orders Currently Stored
Keywords: number taylor coefficient orders currently stored syntax see also purpose f s constructor forward capacity_order example

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Number Taylor Coefficient Orders Currently Stored
Syntax
`s = f.size_order()`
See Also
seq_property
Purpose
Determine the number of Taylor coefficient orders, per variable,direction, currently calculated and stored in the ADFun object `f` . See the discussion under Constructor , Forward , and capacity_order for a description of when this value can change.
f
The object `f` has prototype `
const ADFun<Base> f
`
s
The result `s` has prototype `
size_t s
` and is the number of Taylor coefficient orders, per variable,direction in the AD operation sequence, currently calculated and stored in the ADFun object `f` .
Constructor
Directly after the FunConstruct syntax `
ADFun<Base> f(x, y)
` the value of `s` returned by `size_order` is one. This is because there is an implicit call to `Forward` that computes the zero order Taylor coefficients during this constructor.
Forward
After a call to Forward with the syntax `
f.Forward(q, x_q)
` the value of `s` returned by `size_order` would be q + 1 . The call to `Forward` above uses the lower order Taylor coefficients to compute and store the `q`-th order Taylor coefficients for all the variables in the operation sequence corresponding to `f` . Thus there are q + 1 (order zero through `q` ) Taylor coefficients per variable,direction. (You can determine the number of variables in the operation sequence using the size_var function.)
capacity_order
If the number of Taylor coefficient orders currently stored in `f` is less than or equal `c` , a call to capacity_order with the syntax `
f.capacity_order(c)
` does not affect the value `s` returned by `size_order`. Otherwise, the value `s` returned by `size_order` is equal to `c` (only Taylor coefficients of order zero through c -1 have been retained).
Example
The file forward.cpp contains an example and test of this operation. It returns true if it succeeds and false otherwise.

Input File: omh/forward/size_order.omh