fix: FENCE blocks qubits, not frames

src/program/graph.rs

@@ -21,8 +21,8 @@ use petgraph::graphmap::GraphMap;
 use petgraph::Directed;
 
 use crate::instruction::{
-    FrameIdentifier, Instruction, Jump, JumpUnless, JumpWhen, Label, MeasureCalibrationDefinition,
-    MemoryReference,
+    self, FrameIdentifier, Instruction, Jump, JumpUnless, JumpWhen, Label,
+    MeasureCalibrationDefinition, MemoryReference, Qubit,
 };
 use crate::{instruction::InstructionRole, program::Program};
 
@@ -88,7 +88,7 @@ pub enum ExecutionDependency {
     /// The instructions share a reference frame
     ReferenceFrame,
 
-    /// The ordering between these two instructions must remain unchanged
+    /// The ordering between these two instructions must remain unchanged from the input program
     StableOrdering,
 }
 
@@ -299,6 +299,7 @@ impl InstructionBlock {
 
         // Store the instruction index of the last instruction to block that frame
         let mut last_instruction_by_frame: HashMap<FrameIdentifier, PreviousNodes> = HashMap::new();
+        let mut last_instruction_by_qubit: HashMap<Qubit, PreviousNodes> = HashMap::new();
 
         // Store memory access reads and writes. Key is memory region name.
         // NOTE: this may be refined to serialize by memory region offset rather than by entire region.
@@ -321,34 +322,69 @@ impl InstructionBlock {
                         .get_frames_for_instruction(instruction, false)
                         .unwrap_or_default();
 
-                    let blocked_frames = program
-                        .get_frames_for_instruction(instruction, true)
-                        .unwrap_or_default();
+                    if let Instruction::Fence(instruction::Fence { qubits }) = instruction {
+                        let qubits = if qubits.is_empty() {
+                            program.get_used_qubits()
+                        } else {
+                            qubits.iter().cloned().collect()
+                        };
+
+                        for qubit in qubits {
+                            for previous_node_id in last_instruction_by_qubit
+                                .entry(qubit)
+                                .or_default()
+                                .get_dependencies_for_next_user(node)
+                            {
+                                add_dependency!(graph, previous_node_id => node, ExecutionDependency::StableOrdering)
+                            }
+                        }
 
-                    let blocked_but_not_used_frames = blocked_frames.difference(&used_frames);
+                        Ok(())
+                    } else {
+                        let blocked_frames = program
+                            .get_frames_for_instruction(instruction, true)
+                            .unwrap_or_default();
 
-                    for frame in &used_frames {
-                        let previous_node_ids = last_instruction_by_frame
-                            .entry((*frame).clone())
-                            .or_default()
-                            .get_dependencies_for_next_user(node);
+                        let blocked_but_not_used_frames = blocked_frames.difference(&used_frames);
 
-                        for previous_node_id in previous_node_ids {
-                            add_dependency!(graph, previous_node_id => node, ExecutionDependency::ReferenceFrame);
+                        for frame in &used_frames {
+                            let previous_node_ids = last_instruction_by_frame
+                                .entry((*frame).clone())
+                                .or_default()
+                                .get_dependencies_for_next_user(node);
+
+                            for previous_node_id in previous_node_ids {
+                                add_dependency!(graph, previous_node_id => node, ExecutionDependency::ReferenceFrame);
+                            }
                         }
-                    }
 
-                    for frame in blocked_but_not_used_frames {
-                        if let Some(previous_node_id) = last_instruction_by_frame
-                            .entry((*frame).clone())
-                            .or_default()
-                            .get_dependency_for_next_blocker(node)
-                        {
-                            add_dependency!(graph, previous_node_id => node, ExecutionDependency::ReferenceFrame);
+                        for frame in blocked_but_not_used_frames {
+                            if let Some(previous_node_id) = last_instruction_by_frame
+                                .entry((*frame).clone())
+                                .or_default()
+                                .get_dependency_for_next_blocker(node)
+                            {
+                                add_dependency!(graph, previous_node_id => node, ExecutionDependency::ReferenceFrame);
+                            }
                         }
-                    }
 
-                    Ok(())
+                        let used_qubits = used_frames.iter().fold(HashSet::new(), |mut agg, el| {
+                            agg.extend(&el.qubits);
+                            agg
+                        });
+
+                        for qubit in used_qubits {
+                            if let Some(previous_node_id) = last_instruction_by_qubit
+                                .entry((*qubit).clone())
+                                .or_default()
+                                .get_dependency_for_next_blocker(node)
+                            {
+                                add_dependency!(graph, previous_node_id => node, ExecutionDependency::StableOrdering)
+                            }
+                        }
+
+                        Ok(())
+                    }
                 }
                 InstructionRole::ControlFlow => Err(ScheduleError {
                     instruction_index: Some(index),
@@ -396,6 +432,12 @@ impl InstructionBlock {
             }
         }
 
+        for previous_nodes in last_instruction_by_qubit.into_values() {
+            for node in previous_nodes.drain() {
+                add_dependency!(graph, node => ScheduledGraphNode::BlockEnd, ExecutionDependency::StableOrdering);
+            }
+        }
+
         // Examine all "pending" memory operations for all regions
         let remaining_dependencies = pending_memory_access
             .drain()

src/program/graphviz_dot.rs

@@ -306,8 +306,6 @@ NONBLOCKING PULSE 2 \"rf\" test(duration: 1e6)
 PULSE 0 \"rf\" test(duration: 1e6)
 NONBLOCKING PULSE 0 \"ro_tx\" test(duration: 1e6)
 PULSE 0 \"rf\" test(duration: 1e6)
-FENCE 0
-FENCE 0
 "
         );
 
@@ -352,6 +350,18 @@ FENCE 1
 "
         );
 
+        build_dot_format_snapshot_test_case!(
+            non_overlapping_fence,
+            r#"
+FENCE 0
+NONBLOCKING PULSE 0 "rf" drag_gaussian(alpha: (-0.95146893464447))
+FENCE 0
+FENCE 1
+NONBLOCKING PULSE 1 "rf" drag_gaussian(alpha: (-1.3853631708424974))
+FENCE 1
+"#
+        );
+
         build_dot_format_snapshot_test_case!(
             jump,
             "DECLARE ro BIT

src/program/memory.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::HashSet;
+use std::collections::{BTreeMap, HashSet};
 
 use crate::expression::Expression;
 use crate::instruction::{
@@ -22,6 +22,7 @@ use crate::instruction::{
     Measurement, MemoryReference, Move, Pulse, RawCapture, SetPhase, SetScale, ShiftPhase, Store,
     UnaryLogic, Vector, WaveformInvocation,
 };
+use crate::Program;
 
 #[derive(Clone, Debug, Hash, PartialEq)]
 pub struct MemoryRegion {
@@ -228,13 +229,8 @@ impl Instruction {
                 reads: set_from_memory_references![waveform.get_memory_references()],
                 ..Default::default()
             },
-            Instruction::RawCapture(RawCapture {
-                duration,
-                memory_reference,
-                ..
-            }) => MemoryAccesses {
+            Instruction::RawCapture(RawCapture { duration, .. }) => MemoryAccesses {
                 reads: set_from_memory_references![duration.get_memory_references()],
-                captures: set_from_memory_references![vec![memory_reference]],
                 ..Default::default()
             },
             Instruction::SetPhase(SetPhase { phase: expr, .. })
@@ -315,3 +311,37 @@ impl WaveformInvocation {
         result
     }
 }
+
+impl Program {
+    /// Return all the ways in which a particular [`MemoryReference`] is accessed within a [`Program`].
+    ///
+    /// Note that this does not account for calibration expansion; for accurate results, ensure
+    /// that the program has been fully expanded first.
+    pub fn get_memory_access_types_by_region(&self) -> BTreeMap<String, HashSet<MemoryAccessType>> {
+        let mut result: BTreeMap<String, HashSet<MemoryAccessType>> = BTreeMap::new();
+
+        for instruction in &self.instructions {
+            let accesses = instruction.get_memory_accesses();
+            for region in accesses.reads {
+                result
+                    .entry(region)
+                    .or_default()
+                    .insert(MemoryAccessType::Read);
+            }
+            for region in accesses.writes {
+                result
+                    .entry(region)
+                    .or_default()
+                    .insert(MemoryAccessType::Write);
+            }
+            for region in accesses.captures {
+                result
+                    .entry(region)
+                    .or_default()
+                    .insert(MemoryAccessType::Capture);
+            }
+        }
+
+        result
+    }
+}

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__active_reset_single_frame.snap

@@ -13,10 +13,12 @@ digraph {
     "measure_start" -> "measure_1" [label="frame"];
     "measure_start" -> "measure_end" [label="ordering"];
     "measure_0" [shape=rectangle, label="[0] NONBLOCKING PULSE 0 \"ro_tx\" test(duration: 1000000)"];
-    "measure_0" -> "measure_end" [label="frame"];
+    "measure_0" -> "measure_end" [label="frame
+ordering"];
     "measure_1" [shape=rectangle, label="[1] NONBLOCKING CAPTURE 0 \"ro_rx\" test(duration: 1000000) ro[0]"];
     "measure_1" -> "measure_end" [label="await capture
-frame"];
+frame
+ordering"];
     "measure_end" [shape=circle, label="end"];
   }
   "measure_end" -> "end_start" [label="if ro[0] == 0"];
@@ -29,7 +31,8 @@ frame"];
     "feedback_start" -> "feedback_end" [label="frame
 ordering"];
     "feedback_0" [shape=rectangle, label="[0] PULSE 0 \"rf\" test(duration: 1000000)"];
-    "feedback_0" -> "feedback_end" [label="frame"];
+    "feedback_0" -> "feedback_end" [label="frame
+ordering"];
     "feedback_end" [shape=circle, label="end"];
   }
   "feedback_end" -> "measure_start" [label="always"];

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__blocking_2q_pulse.snap

@@ -16,12 +16,15 @@ digraph {
 ordering"];
     "block_0_0" [shape=rectangle, label="[0] PULSE 0 \"rf\" test(duration: 1e-6)"];
     "block_0_0" -> "block_0_2" [label="frame"];
-    "block_0_0" -> "block_0_end" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] PULSE 1 \"rf\" test(duration: 1e-6)"];
     "block_0_1" -> "block_0_2" [label="frame"];
-    "block_0_1" -> "block_0_end" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] PULSE 0 1 \"cz\" test(duration: 1e-6)"];
-    "block_0_2" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__blocking_pulses_after_nonblocking.snap

@@ -17,12 +17,15 @@ ordering"];
     "block_0_0" [shape=rectangle, label="[0] NONBLOCKING PULSE 0 \"ro_tx\" test(duration: 1000000)"];
     "block_0_0" -> "block_0_1" [label="frame"];
     "block_0_0" -> "block_0_2" [label="frame"];
-    "block_0_0" -> "block_0_end" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_1" -> "block_0_2" [label="frame"];
-    "block_0_1" -> "block_0_end" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] PULSE 0 \"ro_rx\" test(duration: 1000000)"];
-    "block_0_2" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__blocking_pulses_wrap_nonblocking.snap

@@ -11,21 +11,20 @@ digraph {
     "block_0_start" [shape=circle, label="start"];
     "block_0_start" -> "block_0_0" [label="frame"];
     "block_0_start" -> "block_0_1" [label="frame"];
-    "block_0_start" -> "block_0_3" [label="frame"];
-    "block_0_start" -> "block_0_end" [label="ordering"];
+    "block_0_start" -> "block_0_end" [label="frame
+ordering"];
     "block_0_0" [shape=rectangle, label="[0] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_0" -> "block_0_1" [label="frame"];
     "block_0_0" -> "block_0_2" [label="frame"];
-    "block_0_0" -> "block_0_3" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] NONBLOCKING PULSE 0 \"ro_tx\" test(duration: 1000000)"];
     "block_0_1" -> "block_0_2" [label="frame"];
-    "block_0_1" -> "block_0_3" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] PULSE 0 \"rf\" test(duration: 1000000)"];
-    "block_0_2" -> "block_0_3" [label="frame"];
-    "block_0_3" [shape=rectangle, label="[3] FENCE 0"];
-    "block_0_3" -> "block_0_4" [label="frame"];
-    "block_0_4" [shape=rectangle, label="[4] FENCE 0"];
-    "block_0_4" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__chained_pulses.snap

@@ -14,18 +14,23 @@ digraph {
 ordering"];
     "block_0_0" [shape=rectangle, label="[0] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_0" -> "block_0_1" [label="frame"];
-    "block_0_0" -> "block_0_end" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_1" -> "block_0_2" [label="frame"];
-    "block_0_1" -> "block_0_end" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_2" -> "block_0_3" [label="frame"];
-    "block_0_2" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_3" [shape=rectangle, label="[3] PULSE 0 \"rf\" test(duration: 1000000)"];
     "block_0_3" -> "block_0_4" [label="frame"];
-    "block_0_3" -> "block_0_end" [label="frame"];
+    "block_0_3" -> "block_0_end" [label="frame
+ordering"];
     "block_0_4" [shape=rectangle, label="[4] PULSE 0 \"rf\" test(duration: 1000000)"];
-    "block_0_4" -> "block_0_end" [label="frame"];
+    "block_0_4" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__different_frames_blocking.snap

@@ -15,11 +15,14 @@ digraph {
     "block_0_start" -> "block_0_end" [label="frame
 ordering"];
     "block_0_0" [shape=rectangle, label="[0] PULSE 0 \"rf\" test(duration: 1000000)"];
-    "block_0_0" -> "block_0_end" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] PULSE 1 \"rf\" test(duration: 1000000)"];
-    "block_0_1" -> "block_0_end" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] PULSE 2 \"rf\" test(duration: 1000000)"];
-    "block_0_2" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__different_frames_nonblocking.snap

@@ -14,11 +14,14 @@ digraph {
     "block_0_start" -> "block_0_2" [label="frame"];
     "block_0_start" -> "block_0_end" [label="ordering"];
     "block_0_0" [shape=rectangle, label="[0] NONBLOCKING PULSE 0 \"rf\" test(duration: 1000000)"];
-    "block_0_0" -> "block_0_end" [label="frame"];
+    "block_0_0" -> "block_0_end" [label="frame
+ordering"];
     "block_0_1" [shape=rectangle, label="[1] NONBLOCKING PULSE 1 \"rf\" test(duration: 1000000)"];
-    "block_0_1" -> "block_0_end" [label="frame"];
+    "block_0_1" -> "block_0_end" [label="frame
+ordering"];
     "block_0_2" [shape=rectangle, label="[2] NONBLOCKING PULSE 2 \"rf\" test(duration: 1000000)"];
-    "block_0_2" -> "block_0_end" [label="frame"];
+    "block_0_2" -> "block_0_end" [label="frame
+ordering"];
     "block_0_end" [shape=circle, label="end"];
   }
 }

src/program/snapshots/quil_rs__program__graphviz_dot__tests__graph__fence_all.snap

@@ -9,10 +9,8 @@ digraph {
     label="block_0";
     node [style="filled"];
     "block_0_start" [shape=circle, label="start"];
-    "block_0_start" -> "block_0_0" [label="frame"];
     "block_0_start" -> "block_0_end" [label="ordering"];
     "block_0_0" [shape=rectangle, label="[0] FENCE"];
-    "block_0_0" -> "block_0_end" [label="frame"];
     "block_0_end" [shape=circle, label="end"];
   }
 }