# [ADOL-C] Change parameters of a function without retaping

Sat May 9 17:49:32 EDT 2015

The following example demonstrates having a Sparse Hessian w.r.t. one
set of variables and parameters (in the sense below) with respect to
another set of variables.
think that this example could be modified to accomplish your goal below.

Note that one can use ADOLC at the lower level; i.e., use

On 5/8/2015 3:49 PM, Leitz, Thomas wrote:
> Hi,
>
> lets assume I have a function f(x,y) : R^n \times R^m -> R and I only
> need the gradient with respect to x, but every time I need to change
> both variables x and y. (y could be some parameters like coefficients
> of a polynomial function etc.). There are basically two ways I know
> how to achieve this:
>
> 1. mark both x and y as independent variables, tape once and every
> time I need a gradient I compute the whole gradient df/d(x,y) at some
> (x0,y0) and just use df/dx (i.e. the first n values of the gradient
> df/d(x,y)). This way I can change both variables but I also compute
> the gradient df/dy that I don't need.
>
> 2. mark only x as independent and tape the function with any y0 every
> time before computing the gradient df/dx.
>
> Is there any way to tape once, and later compute the gradient df/dx at
> any (x0,y0) without retaping?
>
>
> Thomas

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