Jip J. Dekker
f2a1c4e389
git-subtree-dir: software/mza git-subtree-split: f970a59b177c13ca3dd8aaef8cc6681d83b7e813
33 lines
1.3 KiB
MiniZinc
33 lines
1.3 KiB
MiniZinc
/*
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* Function fzn_piecewise_linear_base creates
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* interval representation of x,
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* which is reusable if we have several pwls
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* on the same set of breakpoints
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*/
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function array[int, int] of var 0.0..1.0: fzn_piecewise_linear_base(
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var float: x, array[int] of float: xi) ::promise_total =
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let {
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set of int: is = index_set(xi),
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set of int: is_1 = is diff { max(is) },
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array[is_1] of var 0.0..1.0: s, %% Segment variables
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array[is_1] of var 0..1: f,
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constraint 1 == sum(f),
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constraint forall(i in is_1)(f[i] >= s[i]),
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constraint x == sum(i in is_1)(xi[i] * f[i] + (xi[i+1]-xi[i]) * s[i]),
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} in
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array2d(is_1, 1..2, f++s);
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predicate fzn_piecewise_linear(var float: x, var float: y,
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array[int] of float: xi, array[int] of float: vi) =
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let {
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set of int: is = index_set(xi),
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constraint assert(is == index_set(vi) /\ 0<card(is),
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"fzn_pwl: index sets unequal or empty"),
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set of int: is_1 = is diff { max(is) },
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array[int, int] of var float: fs = fzn_piecewise_linear_base(x, xi),
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} in
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y == sum(i in is_1)(vi[i] * fs[i, 1] + (vi[i+1]-vi[i]) * fs[i, 2])
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;
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%-----------------------------------------------------------------------------%
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