Jip J. Dekker
fad1b07018
git-subtree-dir: software/minizinc git-subtree-split: 4f10c82056ffcb1041d7ffef29d77a7eef92cf76
33 lines
1.4 KiB
MiniZinc
33 lines
1.4 KiB
MiniZinc
/*
|
|
* Function fzn_piecewise_linear_base creates
|
|
* auxiliary variables for the interval representation of xi
|
|
* and constrains them to correspond to the value of x.
|
|
* The auxiliaries are reusable if we have several pwls
|
|
* on the same set of breakpoints and x.
|
|
*/
|
|
function array[int, int] of var 0.0..1.0: fzn_piecewise_linear_base(
|
|
var float: x, array[int] of float: xi) ::promise_total =
|
|
let {
|
|
set of int: is = index_set(xi),
|
|
set of int: is_1 = is diff { max(is) },
|
|
array[is_1] of var 0.0..1.0: s, %% Segment variables
|
|
array[is_1] of var 0..1: f,
|
|
constraint 1 == sum(f),
|
|
constraint forall(i in is_1)(f[i] >= s[i]),
|
|
constraint x == sum(i in is_1)(xi[i] * f[i] + (xi[i+1]-xi[i]) * s[i]),
|
|
} in
|
|
array2d(1..2, is_1, f++s);
|
|
|
|
predicate fzn_piecewise_linear(var float: x, var float: y,
|
|
array[int] of float: xi, array[int] of float: vi) =
|
|
let {
|
|
set of int: is = index_set(xi),
|
|
constraint assert(is == index_set(vi) /\ 0<card(is),
|
|
"fzn_pwl: index sets unequal or empty"),
|
|
set of int: is_1 = is diff { max(is) },
|
|
array[int, int] of var float: fs = fzn_piecewise_linear_base(x, xi),
|
|
} in
|
|
y == sum(i in is_1)(vi[i] * fs[1, i] + (vi[i+1]-vi[i]) * fs[2, i]);
|
|
|
|
%-----------------------------------------------------------------------------%
|