hugr_core/hugr/patch/
inline_dfg.rs

1//! A rewrite that inlines a DFG node, moving all children
2//! of the DFG except Input+Output into the DFG's parent,
3//! and deleting the DFG along with its Input + Output
4
5use super::{PatchHugrMut, PatchVerification};
6use crate::ops::handle::{DfgID, NodeHandle};
7use crate::{IncomingPort, Node, OutgoingPort, PortIndex};
8
9/// Structure identifying an `InlineDFG` rewrite from the spec
10pub struct InlineDFG(pub DfgID);
11
12/// Errors from an [`InlineDFG`] rewrite.
13#[derive(Clone, Debug, PartialEq, Eq, thiserror::Error)]
14#[non_exhaustive]
15pub enum InlineDFGError {
16    /// Node to inline was not a DFG. (E.g. node has been overwritten since the `DfgID` originated.)
17    #[error("{node} was not a DFG")]
18    NotDFG {
19        /// The node we tried to inline
20        node: Node,
21    },
22    /// The DFG node is the hugr entrypoint
23    #[error("Cannot inline the entrypoint node, {node}")]
24    CantInlineEntrypoint {
25        /// The node we tried to inline
26        node: Node,
27    },
28}
29
30impl PatchVerification for InlineDFG {
31    type Error = InlineDFGError;
32
33    type Node = Node;
34
35    fn verify(&self, h: &impl crate::HugrView<Node = Node>) -> Result<(), Self::Error> {
36        let n = self.0.node();
37        if h.get_optype(n).as_dfg().is_none() {
38            return Err(InlineDFGError::NotDFG { node: n });
39        }
40        if n == h.entrypoint() {
41            return Err(InlineDFGError::CantInlineEntrypoint { node: n });
42        }
43        Ok(())
44    }
45
46    fn invalidation_set(&self) -> impl Iterator<Item = Node> {
47        [self.0.node()].into_iter()
48    }
49}
50
51impl PatchHugrMut for InlineDFG {
52    /// The removed nodes: the DFG, and its Input and Output children.
53    type Outcome = [Node; 3];
54
55    const UNCHANGED_ON_FAILURE: bool = true;
56
57    fn apply_hugr_mut(
58        self,
59        h: &mut impl crate::hugr::HugrMut<Node = Node>,
60    ) -> Result<Self::Outcome, Self::Error> {
61        self.verify(h)?;
62        let n = self.0.node();
63        let (oth_in, oth_out) = {
64            let dfg_ty = h.get_optype(n);
65            (
66                dfg_ty.other_input_port().unwrap(),
67                dfg_ty.other_output_port().unwrap(),
68            )
69        };
70        let parent = h.get_parent(n).unwrap();
71        let [input, output] = h.get_io(n).unwrap();
72        for ch in h.children(n).skip(2).collect::<Vec<_>>() {
73            h.set_parent(ch, parent);
74        }
75        // DFG Inputs. Deal with Order inputs first
76        for (src_n, src_p) in h.linked_outputs(n, oth_in).collect::<Vec<_>>() {
77            // Order edge from src_n to DFG => add order edge to each successor of Input node
78            debug_assert_eq!(Some(src_p), h.get_optype(src_n).other_output_port());
79            for tgt_n in h.output_neighbours(input).collect::<Vec<_>>() {
80                h.add_other_edge(src_n, tgt_n);
81            }
82        }
83        // And remaining (Value) inputs
84        let input_ord_succs = h
85            .linked_inputs(input, h.get_optype(input).other_output_port().unwrap())
86            .collect::<Vec<_>>();
87        for inp in h.node_inputs(n).collect::<Vec<_>>() {
88            if inp == oth_in {
89                continue;
90            }
91            // Hugr is invalid if there is no output linked to the DFG input.
92            let (src_n, src_p) = h.single_linked_output(n, inp).unwrap();
93            h.disconnect(n, inp); // These disconnects allow permutations to work trivially.
94            let outp = OutgoingPort::from(inp.index());
95            let targets = h.linked_inputs(input, outp).collect::<Vec<_>>();
96            h.disconnect(input, outp);
97
98            for (tgt_n, tgt_p) in targets {
99                h.connect(src_n, src_p, tgt_n, tgt_p);
100            }
101            // Ensure order-successors of Input node execute after any node producing an input
102            for (tgt, _) in &input_ord_succs {
103                h.add_other_edge(src_n, *tgt);
104            }
105        }
106        // DFG Outputs. Deal with Order outputs first.
107        for (tgt_n, tgt_p) in h.linked_inputs(n, oth_out).collect::<Vec<_>>() {
108            debug_assert_eq!(Some(tgt_p), h.get_optype(tgt_n).other_input_port());
109            for src_n in h.input_neighbours(output).collect::<Vec<_>>() {
110                h.add_other_edge(src_n, tgt_n);
111            }
112        }
113        // And remaining (Value) outputs
114        let output_ord_preds = h
115            .linked_outputs(output, h.get_optype(output).other_input_port().unwrap())
116            .collect::<Vec<_>>();
117        for outport in h.node_outputs(n).collect::<Vec<_>>() {
118            if outport == oth_out {
119                continue;
120            }
121            let inpp = IncomingPort::from(outport.index());
122            // Hugr is invalid if the Output node has no corresponding input
123            let (src_n, src_p) = h.single_linked_output(output, inpp).unwrap();
124            h.disconnect(output, inpp);
125
126            for (tgt_n, tgt_p) in h.linked_inputs(n, outport).collect::<Vec<_>>() {
127                h.connect(src_n, src_p, tgt_n, tgt_p);
128                // Ensure order-predecessors of Output node execute before any node consuming a DFG output
129                for (src, _) in &output_ord_preds {
130                    h.add_other_edge(*src, tgt_n);
131                }
132            }
133            h.disconnect(n, outport);
134        }
135        h.remove_node(input);
136        h.remove_node(output);
137        assert!(h.children(n).next().is_none());
138        h.remove_node(n);
139        Ok([n, input, output])
140    }
141}
142
143#[cfg(test)]
144mod test {
145    use std::collections::HashSet;
146
147    use rstest::rstest;
148
149    use crate::builder::{
150        Container, DFGBuilder, Dataflow, DataflowHugr, DataflowSubContainer, SubContainer,
151        endo_sig, inout_sig,
152    };
153    use crate::extension::prelude::qb_t;
154    use crate::hugr::HugrMut;
155    use crate::ops::handle::{DfgID, NodeHandle};
156    use crate::ops::{OpType, Value};
157    use crate::std_extensions::arithmetic::float_types;
158    use crate::std_extensions::arithmetic::int_ops::IntOpDef;
159    use crate::std_extensions::arithmetic::int_types::{self, ConstInt};
160    use crate::types::Signature;
161    use crate::utils::test_quantum_extension;
162    use crate::{Direction, HugrView, Port, type_row};
163    use crate::{Hugr, Wire};
164
165    use super::InlineDFG;
166
167    fn find_dfgs<H: HugrView>(h: &H) -> Vec<H::Node> {
168        h.entry_descendants()
169            .filter(|n| h.get_optype(*n).as_dfg().is_some())
170            .collect()
171    }
172    fn extension_ops<H: HugrView>(h: &H) -> Vec<H::Node> {
173        h.nodes()
174            .filter(|n| matches!(h.get_optype(*n), OpType::ExtensionOp(_)))
175            .collect()
176    }
177
178    #[rstest]
179    #[case(true)]
180    #[case(false)]
181    fn inline_add_load_const(#[case] nonlocal: bool) -> Result<(), Box<dyn std::error::Error>> {
182        use crate::hugr::patch::inline_dfg::InlineDFGError;
183
184        let int_ty = &int_types::INT_TYPES[6];
185
186        let mut outer = DFGBuilder::new(inout_sig(vec![int_ty.clone(); 2], vec![int_ty.clone()]))?;
187        let [a, b] = outer.input_wires_arr();
188        fn make_const<T: AsMut<Hugr> + AsRef<Hugr>>(
189            d: &mut DFGBuilder<T>,
190        ) -> Result<Wire, Box<dyn std::error::Error>> {
191            let cst = Value::extension(ConstInt::new_u(6, 15)?);
192            let c1 = d.add_load_const(cst);
193
194            Ok(c1)
195        }
196        let c1 = nonlocal.then(|| make_const(&mut outer));
197        let inner = {
198            let mut inner = outer.dfg_builder_endo([(int_ty.clone(), a)])?;
199            let [a] = inner.input_wires_arr();
200            let c1 = c1.unwrap_or_else(|| make_const(&mut inner))?;
201            let a1 = inner.add_dataflow_op(IntOpDef::iadd.with_log_width(6), [a, c1])?;
202            inner.finish_with_outputs(a1.outputs())?
203        };
204        let [a1] = inner.outputs_arr();
205
206        let a1_sub_b = outer.add_dataflow_op(IntOpDef::isub.with_log_width(6), [a1, b])?;
207        let mut outer = outer.finish_hugr_with_outputs(a1_sub_b.outputs())?;
208
209        // Sanity checks
210        assert_eq!(
211            outer.children(inner.node()).count(),
212            if nonlocal { 3 } else { 5 }
213        ); // Input, Output, add; + const, load_const
214        assert_eq!(find_dfgs(&outer), vec![outer.entrypoint(), inner.node()]);
215        let [add, sub] = extension_ops(&outer).try_into().unwrap();
216        assert_eq!(
217            outer.get_parent(outer.get_parent(add).unwrap()),
218            outer.get_parent(sub)
219        );
220        assert_eq!(outer.entry_descendants().count(), 10); // 6 above + inner DFG + outer (DFG + Input + Output + sub)
221        {
222            // Check we can't inline the outer DFG
223            let mut h = outer.clone();
224            assert_eq!(
225                h.apply_patch(InlineDFG(DfgID::from(h.entrypoint()))),
226                Err(InlineDFGError::CantInlineEntrypoint {
227                    node: h.entrypoint()
228                })
229            );
230            assert_eq!(h, outer); // unchanged
231        }
232
233        outer.apply_patch(InlineDFG(*inner.handle()))?;
234        outer.validate()?;
235        assert_eq!(outer.entry_descendants().count(), 7);
236        assert_eq!(find_dfgs(&outer), vec![outer.entrypoint()]);
237        let [add, sub] = extension_ops(&outer).try_into().unwrap();
238        assert_eq!(outer.get_parent(add), Some(outer.entrypoint()));
239        assert_eq!(outer.get_parent(sub), Some(outer.entrypoint()));
240        assert_eq!(
241            outer.node_connections(add, sub).collect::<Vec<_>>().len(),
242            1
243        );
244        Ok(())
245    }
246
247    #[test]
248    fn permutation() -> Result<(), Box<dyn std::error::Error>> {
249        let mut h = DFGBuilder::new(endo_sig(vec![qb_t(), qb_t()]))?;
250        let [p, q] = h.input_wires_arr();
251        let [p_h] = h
252            .add_dataflow_op(test_quantum_extension::h_gate(), [p])?
253            .outputs_arr();
254        let swap = {
255            let swap = h.dfg_builder(Signature::new_endo(vec![qb_t(), qb_t()]), [p_h, q])?;
256            let [a, b] = swap.input_wires_arr();
257            swap.finish_with_outputs([b, a])?
258        };
259        let [q, p] = swap.outputs_arr();
260        let cx = h.add_dataflow_op(test_quantum_extension::cx_gate(), [q, p])?;
261
262        let mut h = h.finish_hugr_with_outputs(cx.outputs())?;
263        assert_eq!(find_dfgs(&h), vec![h.entrypoint(), swap.node()]);
264        assert_eq!(h.entry_descendants().count(), 8); // Dfg+I+O, H, CX, Dfg+I+O
265        // No permutation outside the swap DFG:
266        assert_eq!(
267            h.node_connections(p_h.node(), swap.node())
268                .collect::<Vec<_>>(),
269            vec![[
270                Port::new(Direction::Outgoing, 0),
271                Port::new(Direction::Incoming, 0)
272            ]]
273        );
274        assert_eq!(
275            h.node_connections(swap.node(), cx.node())
276                .collect::<Vec<_>>(),
277            vec![
278                [
279                    Port::new(Direction::Outgoing, 0),
280                    Port::new(Direction::Incoming, 0)
281                ],
282                [
283                    Port::new(Direction::Outgoing, 1),
284                    Port::new(Direction::Incoming, 1)
285                ]
286            ]
287        );
288
289        h.apply_patch(InlineDFG(*swap.handle()))?;
290        assert_eq!(find_dfgs(&h), vec![h.entrypoint()]);
291        assert_eq!(h.entry_descendants().count(), 5); // Dfg+I+O
292        let mut ops = extension_ops(&h);
293        ops.sort_by_key(|n| h.num_outputs(*n)); // Put H before CX
294        let [h_gate, cx] = ops.try_into().unwrap();
295        // Now permutation exists:
296        assert_eq!(
297            h.node_connections(h_gate, cx).collect::<Vec<_>>(),
298            vec![[
299                Port::new(Direction::Outgoing, 0),
300                Port::new(Direction::Incoming, 1)
301            ]]
302        );
303        Ok(())
304    }
305
306    #[test]
307    fn order_edges() -> Result<(), Box<dyn std::error::Error>> {
308        /*      -----|-----|-----
309         *           |     |
310         *          H_a   H_b
311         *           |.    /         NB. Order edge H_a to nested DFG
312         *           | .  |
313         *           |  /-|--------\
314         *           |  | | .  Cst | NB. Order edge Input to LCst
315         *           |  | |  . |   |
316         *           |  | |   LCst |
317         *           |  |  \ /     |
318         *           |  |  RZ      |
319         *           |  |  |       |
320         *           |  |  meas    |
321         *           |  |  | \     |
322         *           |  |  |  if   |
323         *           |  |  |  .    | NB. Order edge if to Output
324         *           |  \--|-------/
325         *           |  .  |
326         *           | .   |         NB. Order edge nested DFG to H_a2
327         *           H_a2  /
328         *             \  /
329         *              CX
330         */
331        // Extension inference here relies on quantum ops not requiring their own test_quantum_extension
332        let mut outer = DFGBuilder::new(endo_sig(vec![qb_t(), qb_t()]))?;
333        let [a, b] = outer.input_wires_arr();
334        let h_a = outer.add_dataflow_op(test_quantum_extension::h_gate(), [a])?;
335        let h_b = outer.add_dataflow_op(test_quantum_extension::h_gate(), [b])?;
336        let mut inner = outer.dfg_builder(endo_sig(qb_t()), h_b.outputs())?;
337        let [i] = inner.input_wires_arr();
338        let f = inner.add_load_value(float_types::ConstF64::new(1.0));
339        inner.add_other_wire(inner.input().node(), f.node());
340        let r = inner.add_dataflow_op(test_quantum_extension::rz_f64(), [i, f])?;
341        let [m, b] = inner
342            .add_dataflow_op(test_quantum_extension::measure(), r.outputs())?
343            .outputs_arr();
344        // Node using the boolean. Here we just select between two empty computations.
345        let mut if_n =
346            inner.conditional_builder(([type_row![], type_row![]], b), [], type_row![])?;
347        if_n.case_builder(0)?.finish_with_outputs([])?;
348        if_n.case_builder(1)?.finish_with_outputs([])?;
349        let if_n = if_n.finish_sub_container()?;
350        inner.add_other_wire(if_n.node(), inner.output().node());
351        let inner = inner.finish_with_outputs([m])?;
352        outer.add_other_wire(h_a.node(), inner.node());
353        let h_a2 = outer.add_dataflow_op(test_quantum_extension::h_gate(), h_a.outputs())?;
354        outer.add_other_wire(inner.node(), h_a2.node());
355        let cx = outer.add_dataflow_op(
356            test_quantum_extension::cx_gate(),
357            h_a2.outputs().chain(inner.outputs()),
358        )?;
359        let mut outer = outer.finish_hugr_with_outputs(cx.outputs())?;
360
361        outer.apply_patch(InlineDFG(*inner.handle()))?;
362        outer.validate()?;
363        let order_neighbours = |n, d| {
364            let p = outer.get_optype(n).other_port(d).unwrap();
365            outer
366                .linked_ports(n, p)
367                .map(|(n, _)| n)
368                .collect::<HashSet<_>>()
369        };
370        // h_a should have Order edges added to Rz and the F64 load_const
371        assert_eq!(
372            order_neighbours(h_a.node(), Direction::Outgoing),
373            HashSet::from([r.node(), f.node()])
374        );
375        // Likewise the load_const should have Order edges from the inputs to the inner DFG, i.e. h_a and h_b
376        assert_eq!(
377            order_neighbours(f.node(), Direction::Incoming),
378            HashSet::from([h_a.node(), h_b.node()])
379        );
380        // h_a2 should have Order edges from the measure and if
381        assert_eq!(
382            order_neighbours(h_a2.node(), Direction::Incoming),
383            HashSet::from([m.node(), if_n.node()])
384        );
385        // the if should have Order edges to the CX and h_a2
386        assert_eq!(
387            order_neighbours(if_n.node(), Direction::Outgoing),
388            HashSet::from([h_a2.node(), cx.node()])
389        );
390        Ok(())
391    }
392}
hugr_core/hugr/patch/inline_dfg.rs

hugr_core/hugr/patch/
inline_dfg.rs
