Add aigcxemin and cexenum.py tools

tools/aigcexmin/src/aig_eval.rs

@@ -0,0 +1,104 @@
+use flussab_aiger::{aig::OrderedAig, Lit};
+
+use crate::util::unpack_lit;
+
+pub trait AigValue<Context>: Copy {
+    fn invert_if(self, en: bool, ctx: &mut Context) -> Self;
+    fn and(self, other: Self, ctx: &mut Context) -> Self;
+    fn constant(value: bool, ctx: &mut Context) -> Self;
+}
+
+pub fn initial_frame<L, V, Context>(
+    aig: &OrderedAig<L>,
+    state: &mut Vec<V>,
+    mut latch_init: impl FnMut(usize, &mut Context) -> V,
+    mut input: impl FnMut(usize, &mut Context) -> V,
+    ctx: &mut Context,
+) where
+    L: Lit,
+    V: AigValue<Context>,
+{
+    state.clear();
+    state.push(V::constant(false, ctx));
+
+    for i in 0..aig.input_count {
+        state.push(input(i, ctx));
+    }
+
+    for i in 0..aig.latches.len() {
+        state.push(latch_init(i, ctx));
+    }
+
+    for and_gate in aig.and_gates.iter() {
+        let [a, b] = and_gate.inputs.map(|lit| {
+            let (var, polarity) = unpack_lit(lit);
+            state[var].invert_if(polarity, ctx)
+        });
+
+        state.push(a.and(b, ctx));
+    }
+}
+
+pub fn successor_frame<L, V, Context>(
+    aig: &OrderedAig<L>,
+    state: &mut Vec<V>,
+    mut input: impl FnMut(usize, &mut Context) -> V,
+    ctx: &mut Context,
+) where
+    L: Lit,
+    V: AigValue<Context>,
+{
+    assert_eq!(state.len(), 1 + aig.max_var_index);
+
+    for i in 0..aig.input_count {
+        state.push(input(i, ctx));
+    }
+
+    for latch in aig.latches.iter() {
+        let (var, polarity) = unpack_lit(latch.next_state);
+        state.push(state[var].invert_if(polarity, ctx));
+    }
+
+    state.drain(1..1 + aig.max_var_index);
+
+    for and_gate in aig.and_gates.iter() {
+        let [a, b] = and_gate.inputs.map(|lit| {
+            let (var, polarity) = unpack_lit(lit);
+            state[var].invert_if(polarity, ctx)
+        });
+
+        state.push(a.and(b, ctx));
+    }
+}
+
+impl AigValue<()> for bool {
+    fn invert_if(self, en: bool, _ctx: &mut ()) -> Self {
+        self ^ en
+    }
+
+    fn and(self, other: Self, _ctx: &mut ()) -> Self {
+        self & other
+    }
+
+    fn constant(value: bool, _ctx: &mut ()) -> Self {
+        value
+    }
+}
+
+impl AigValue<()> for Option<bool> {
+    fn invert_if(self, en: bool, _ctx: &mut ()) -> Self {
+        self.map(|b| b ^ en)
+    }
+
+    fn and(self, other: Self, _ctx: &mut ()) -> Self {
+        match (self, other) {
+            (Some(true), Some(true)) => Some(true),
+            (Some(false), _) | (_, Some(false)) => Some(false),
+            _ => None,
+        }
+    }
+
+    fn constant(value: bool, _ctx: &mut ()) -> Self {
+        Some(value)
+    }
+}

tools/aigcexmin/src/care_graph.rs

@@ -0,0 +1,730 @@
+use std::{
+    cmp::Reverse,
+    collections::{BTreeSet, BinaryHeap},
+    mem::{replace, take},
+    num::NonZeroU32,
+};
+
+use color_eyre::eyre::bail;
+use flussab::DeferredWriter;
+use flussab_aiger::{aig::OrderedAig, Lit};
+use zwohash::HashMap;
+
+use crate::{
+    aig_eval::{initial_frame, successor_frame, AigValue},
+    util::{unpack_lit, write_output_bit},
+};
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[repr(transparent)]
+pub struct NodeRef {
+    code: Reverse<NonZeroU32>,
+}
+
+impl std::fmt::Debug for NodeRef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_tuple("NodeRef::new").field(&self.index()).finish()
+    }
+}
+
+impl NodeRef {
+    const INVALID_INDEX: usize = u32::MAX as usize;
+    const TRUE_INDEX: usize = Self::INVALID_INDEX - 1;
+    const FALSE_INDEX: usize = Self::INVALID_INDEX - 2;
+
+    pub const TRUE: Self = Self::new(Self::TRUE_INDEX);
+    pub const FALSE: Self = Self::new(Self::FALSE_INDEX);
+
+    pub const fn new(index: usize) -> Self {
+        assert!(index < u32::MAX as usize);
+        let Some(code) = NonZeroU32::new(!(index as u32)) else {
+            unreachable!();
+        };
+        Self {
+            code: Reverse(code),
+        }
+    }
+
+    pub fn index(self) -> usize {
+        !(self.code.0.get()) as usize
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+enum Gate {
+    And,
+    Or,
+}
+
+#[derive(Debug)]
+enum NodeDef {
+    Gate([NodeRef; 2]),
+    Input(u32),
+}
+
+impl NodeDef {
+    fn and(inputs: [NodeRef; 2]) -> Self {
+        assert!(inputs[0] < inputs[1]);
+        Self::Gate(inputs)
+    }
+
+    fn or(inputs: [NodeRef; 2]) -> Self {
+        assert!(inputs[0] < inputs[1]);
+        Self::Gate([inputs[1], inputs[0]])
+    }
+
+    fn input(id: u32) -> Self {
+        Self::Input(id)
+    }
+
+    fn as_gate(&self) -> Result<(Gate, [NodeRef; 2]), u32> {
+        match *self {
+            NodeDef::Gate(inputs) => {
+                if inputs[0] < inputs[1] {
+                    Ok((Gate::And, inputs))
+                } else {
+                    Ok((Gate::Or, [inputs[1], inputs[0]]))
+                }
+            }
+            NodeDef::Input(input) => Err(input),
+        }
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Default, Debug)]
+enum NodeState {
+    #[default]
+    Unknown,
+    Nonselected,
+    Selected,
+    Required,
+}
+
+#[derive(Debug)]
+struct Node {
+    def: NodeDef,
+    priority: u32,
+    state: NodeState,
+    renamed: Option<NodeRef>,
+}
+
+impl Node {
+    fn update_state(&mut self, state: NodeState) -> NodeState {
+        let old_state = self.state;
+        self.state = self.state.max(state);
+        old_state
+    }
+}
+
+#[derive(Default)]
+pub struct AndOrGraph {
+    find_input: HashMap<u32, NodeRef>,
+    find_and: HashMap<[NodeRef; 2], NodeRef>,
+    find_or: HashMap<[NodeRef; 2], NodeRef>,
+
+    // find_renamed: HashMap<NodeRef, NodeRef>,
+    nodes: Vec<Node>,
+    queue: BinaryHeap<NodeRef>,
+    stack: Vec<NodeRef>,
+
+    unknown_inputs: BTreeSet<u32>,
+    required_inputs: BTreeSet<u32>,
+    active_node_count: usize,
+
+    input_order: Vec<(NodeRef, u32)>,
+    cache: bool,
+}
+
+impl AndOrGraph {
+    pub fn input(&mut self, id: u32) -> NodeRef {
+        assert!(id <= u32::MAX - 2);
+        *self.find_input.entry(id).or_insert_with(|| {
+            let node_ref = NodeRef::new(self.nodes.len());
+            let node = Node {
+                def: NodeDef::input(id),
+                priority: id,
+                state: NodeState::Unknown,
+                renamed: None,
+            };
+            self.nodes.push(node);
+            self.unknown_inputs.insert(id);
+            node_ref
+        })
+    }
+
+    pub fn and(&mut self, mut inputs: [NodeRef; 2]) -> NodeRef {
+        inputs.sort_unstable();
+        if inputs[1] == NodeRef::FALSE {
+            NodeRef::FALSE
+        } else if inputs[1] == NodeRef::TRUE || inputs[1] == inputs[0] {
+            inputs[0]
+        } else {
+            let [a, b] = inputs;
+            match inputs.map(|input| self.nodes[input.index()].def.as_gate()) {
+                [Ok((Gate::And, [a0, a1])), _] if b == a0 || b == a1 => {
+                    return a;
+                }
+                [_, Ok((Gate::And, [b0, b1]))] if a == b0 || a == b1 => {
+                    return b;
+                }
+
+                [Ok((Gate::Or, [a0, a1])), _] if b == a0 || b == a1 => {
+                    return b;
+                }
+                [_, Ok((Gate::Or, [b0, b1]))] if a == b0 || a == b1 => {
+                    return a;
+                }
+
+                _ => (),
+            }
+
+            let mut mknode = || {
+                let node_ref = NodeRef::new(self.nodes.len());
+
+                let [a, b] = inputs.map(|input| self.nodes[input.index()].priority);
+
+                let node = Node {
+                    def: NodeDef::and(inputs),
+                    priority: a.min(b),
+                    state: NodeState::Unknown,
+                    renamed: None,
+                };
+                self.nodes.push(node);
+                node_ref
+            };
+
+            if self.cache {
+                *self.find_and.entry(inputs).or_insert_with(mknode)
+            } else {
+                mknode()
+            }
+        }
+    }
+
+    pub fn or(&mut self, mut inputs: [NodeRef; 2]) -> NodeRef {
+        inputs.sort_unstable();
+
+        if inputs[1] == NodeRef::TRUE {
+            NodeRef::TRUE
+        } else if inputs[1] == NodeRef::FALSE || inputs[1] == inputs[0] {
+            inputs[0]
+        } else {
+            let [a, b] = inputs;
+            match inputs.map(|input| self.nodes[input.index()].def.as_gate()) {
+                [Ok((Gate::Or, [a0, a1])), _] if b == a0 || b == a1 => {
+                    return a;
+                }
+                [_, Ok((Gate::Or, [b0, b1]))] if a == b0 || a == b1 => {
+                    return b;
+                }
+
+                [Ok((Gate::And, [a0, a1])), _] if b == a0 || b == a1 => {
+                    return b;
+                }
+                [_, Ok((Gate::And, [b0, b1]))] if a == b0 || a == b1 => {
+                    return a;
+                }
+
+                _ => (),
+            }
+
+            let mut mknode = || {
+                let node_ref = NodeRef::new(self.nodes.len());
+
+                let [a, b] = inputs.map(|input| self.nodes[input.index()].priority);
+
+                let node = Node {
+                    def: NodeDef::or(inputs),
+                    priority: a.max(b),
+                    state: NodeState::Unknown,
+                    renamed: None,
+                };
+                self.nodes.push(node);
+                node_ref
+            };
+
+            if self.cache {
+                *self.find_or.entry(inputs).or_insert_with(mknode)
+            } else {
+                mknode()
+            }
+        }
+    }
+
+    pub fn pass(&mut self, target: NodeRef, shuffle: usize, mut enable_cache: bool) -> NodeRef {
+        if self.cache {
+            enable_cache = false;
+        }
+
+        self.nodes[target.index()].state = NodeState::Required;
+        self.queue.push(target);
+
+        let target_priority = self.nodes[target.index()].priority;
+
+        'queue: while let Some(current) = self.queue.pop() {
+            let node = &self.nodes[current.index()];
+            let state = node.state;
+
+            self.stack.push(current);
+
+            match node.def.as_gate() {
+                Ok((Gate::And, inputs)) => {
+                    if enable_cache {
+                        self.find_and.insert(inputs, current);
+                    }
+                    for input in inputs {
+                        let node = &mut self.nodes[input.index()];
+                        if node.update_state(state) == NodeState::Unknown {
+                            self.queue.push(input);
+                        }
+                    }
+                }
+                Ok((Gate::Or, inputs)) => {
+                    if enable_cache {
+                        self.find_or.insert(inputs, current);
+                    }
+                    for input in inputs {
+                        let node = &mut self.nodes[input.index()];
+                        if node.update_state(NodeState::Nonselected) == NodeState::Unknown {
+                            self.queue.push(input);
+                        }
+                    }
+
+                    if state <= NodeState::Nonselected {
+                        continue;
+                    }
+
+                    let input_priorities = inputs.map(|input| self.nodes[input.index()].priority);
+
+                    for (i, input_priority) in input_priorities.into_iter().enumerate() {
+                        if input_priority < target_priority {
+                            // The other input will be false, so propagate the state
+                            self.nodes[inputs[i ^ 1].index()].update_state(state);
+                            continue;
+                        }
+                    }
+
+                    for input in inputs {
+                        let input_state = self.nodes[input.index()].state;
+                        if input_state >= NodeState::Selected {
+                            // One input of the or is already marked, no need to mark the other
+                            continue 'queue;
+                        }
+                    }
+
+                    // Mark the highest priority input
+                    let input = inputs[(input_priorities[1] > input_priorities[0]) as usize];
+                    self.nodes[input.index()].update_state(NodeState::Selected);
+                }
+                Err(_input) => (),
+            }
+        }
+
+        if enable_cache {
+            self.cache = true;
+        }
+
+        let mut stack = take(&mut self.stack);
+
+        self.active_node_count = stack.len();
+
+        self.unknown_inputs.clear();
+
+        for current in stack.drain(..).rev() {
+            let node = &mut self.nodes[current.index()];
+            let state = replace(&mut node.state, NodeState::Unknown);
+            let priority = node.priority;
+
+            match node.def.as_gate() {
+                Ok((gate, inputs)) => {
+                    let new_inputs = inputs.map(|input| self.nodes[input.index()].renamed.unwrap());
+
+                    let output = if new_inputs == inputs {
+                        current
+                    } else {
+                        match gate {
+                            Gate::And => self.and(new_inputs),
+                            Gate::Or => self.or(new_inputs),
+                        }
+                    };
+
+                    if shuffle > 0 && output != NodeRef::FALSE && output != NodeRef::TRUE {
+                        if let Ok((gate, inputs)) = self.nodes[output.index()].def.as_gate() {
+                            let [a, b] = inputs.map(|input| self.nodes[input.index()].priority);
+
+                            self.nodes[output.index()].priority = match gate {
+                                Gate::And => a.min(b),
+                                Gate::Or => a.max(b),
+                            };
+                        }
+                    }
+
+                    self.nodes[current.index()].renamed = Some(output);
+                }
+                Err(input) => match priority.cmp(&target_priority) {
+                    std::cmp::Ordering::Less => {
+                        self.nodes[current.index()].renamed = Some(NodeRef::FALSE);
+                    }
+                    std::cmp::Ordering::Equal => {
+                        self.required_inputs.insert(input);
+                        self.nodes[current.index()].renamed = Some(NodeRef::TRUE);
+                    }
+                    std::cmp::Ordering::Greater => match state {
+                        NodeState::Required => {
+                            self.required_inputs.insert(input);
+                            self.nodes[current.index()].renamed = Some(NodeRef::TRUE);
+                        }
+                        NodeState::Selected => {
+                            self.unknown_inputs.insert(input);
+                            self.nodes[current.index()].renamed = Some(current);
+
+                            if shuffle > 0 {
+                                let priority = &mut self.nodes[current.index()].priority;
+                                let mask = !(u64::MAX << 32.min(shuffle - 1)) as u32;
+
+                                *priority ^=
+                                    !(*priority ^ priority.wrapping_mul(0x2c9277b5)) & mask;
+                            }
+                        }
+                        NodeState::Nonselected => {
+                            self.nodes[current.index()].renamed = Some(NodeRef::FALSE);
+                        }
+                        NodeState::Unknown => {
+                            unreachable!();
+                        }
+                    },
+                },
+            }
+        }
+
+        self.input_order.clear();
+
+        let result = self.nodes[target.index()].renamed.unwrap();
+        self.stack = stack;
+
+        result
+    }
+}
+
+impl AigValue<AndOrGraph> for (Option<bool>, NodeRef) {
+    fn invert_if(self, en: bool, _: &mut AndOrGraph) -> Self {
+        let (value, care) = self;
+        (value.map(|b| b ^ en), care)
+    }
+
+    fn and(self, other: Self, ctx: &mut AndOrGraph) -> Self {
+        let (value_a, care_a) = self;
+        let (value_b, care_b) = other;
+
+        match (value_a, value_b) {
+            (Some(true), Some(true)) => (Some(true), ctx.and([care_a, care_b])),
+            (Some(false), Some(false)) => (Some(false), ctx.or([care_a, care_b])),
+            (Some(false), _) => (Some(false), care_a),
+            (_, Some(false)) => (Some(false), care_b),
+            _ => (None, NodeRef::FALSE),
+        }
+    }
+
+    fn constant(value: bool, _: &mut AndOrGraph) -> Self {
+        (Some(value), NodeRef::TRUE)
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum Verification {
+    Cex,
+    Full,
+}
+
+pub struct MinimizationOptions {
+    pub fixed_init: bool,
+    pub verify: Option<Verification>,
+}
+
+pub fn minimize<L: Lit>(
+    aig: &OrderedAig<L>,
+    latch_init: &[Option<bool>],
+    frame_inputs: &[Vec<Option<bool>>],
+    writer: &mut DeferredWriter,
+    options: &MinimizationOptions,
+) -> color_eyre::Result<()> {
+    let Some(initial_inputs) = frame_inputs.first() else {
+        bail!("no inputs found");
+    };
+
+    let mut state = vec![];
+
+    let mut graph = AndOrGraph::default();
+
+    let input_id = |frame: Option<usize>, index: usize| -> u32 {
+        (if let Some(frame) = frame {
+            latch_init.len() + frame * initial_inputs.len() + index
+        } else {
+            index
+        })
+        .try_into()
+        .unwrap()
+    };
+
+    let decode_input_id = |id: u32| -> (Option<usize>, usize) {
+        let id = id as usize;
+        if id < latch_init.len() {
+            (None, id)
+        } else {
+            let id = id - latch_init.len();
+            let frame = id / initial_inputs.len();
+            let index = id % initial_inputs.len();
+            (Some(frame), index)
+        }
+    };
+
+    initial_frame(
+        aig,
+        &mut state,
+        |i, ctx| {
+            (
+                latch_init[i],
+                if latch_init[i].is_some() {
+                    if options.fixed_init {
+                        NodeRef::TRUE
+                    } else {
+                        ctx.input(input_id(None, i))
+                    }
+                } else {
+                    NodeRef::FALSE
+                },
+            )
+        },
+        |i, ctx| {
+            (
+                initial_inputs[i],
+                if initial_inputs[i].is_some() {
+                    ctx.input(input_id(Some(0), i))
+                } else {
+                    NodeRef::FALSE
+                },
+            )
+        },
+        &mut graph,
+    );
+
+    let mut minimization_target = 'minimization_target: {
+        for (t, inputs) in frame_inputs.iter().enumerate() {
+            if t > 0 {
+                successor_frame(
+                    aig,
+                    &mut state,
+                    |i, ctx| {
+                        (
+                            inputs[i],
+                            if inputs[i].is_some() {
+                                ctx.input(input_id(Some(t), i))
+                            } else {
+                                NodeRef::FALSE
+                            },
+                        )
+                    },
+                    &mut graph,
+                );
+            }
+            let mut good_state = (Some(true), NodeRef::TRUE);
+
+            for (i, bad) in aig.bad_state_properties.iter().enumerate() {
+                let (var, polarity) = unpack_lit(*bad);
+                let inv_bad = state[var].invert_if(!polarity, &mut graph);
+
+                if inv_bad.0 == Some(false) {
+                    println!("bad state property {i} active in frame {t}");
+                }
+
+                good_state = good_state.and(inv_bad, &mut graph);
+            }
+            if good_state.0 == Some(false) {
+                println!("bad state found in frame {t}");
+
+                break 'minimization_target good_state.1;
+            }
+
+            if t > 0 && t % 500 == 0 {
+                println!(
+                    "traced frame {t}/{frames}: node count = {node_count}",
+                    frames = frame_inputs.len(),
+                    node_count = graph.nodes.len(),
+                );
+            }
+        }
+
+        bail!("no bad state found");
+    };
+
+    let node_count_width = (graph.nodes.len().max(2) - 1).ilog10() as usize + 1;
+    let input_count_width = (graph.unknown_inputs.len().max(2) - 1).ilog10() as usize + 1;
+
+    println!(
+        "input: node count = {node_count:w0$}, defined inputs = {defined_inputs:w1$}",
+        node_count = graph.nodes.len(),
+        defined_inputs = graph.unknown_inputs.len(),
+        w0 = node_count_width,
+        w1 = input_count_width,
+    );
+
+    let mut shuffle = 0;
+
+    let mut iteration = 0;
+
+    while minimization_target != NodeRef::TRUE {
+        let prev_unknown_inputs = graph.unknown_inputs.len();
+        minimization_target = graph.pass(minimization_target, shuffle, iteration >= 1);
+        let unknown_inputs = graph.unknown_inputs.len();
+        let required_inputs = graph.required_inputs.len();
+        println!(
+            concat!(
+                "iter:  node count = {node_count:w0$}, defined inputs = {defined_inputs:w1$}, ",
+                "required inputs = {required_inputs:w1$}, shuffle = {shuffle}"
+            ),
+            node_count = graph.active_node_count,
+            required_inputs = required_inputs,
+            defined_inputs = unknown_inputs + required_inputs,
+            shuffle = shuffle,
+            w0 = node_count_width,
+            w1 = input_count_width,
+        );
+
+        if unknown_inputs + (unknown_inputs / 4) < prev_unknown_inputs {
+            shuffle = 0;
+        } else {
+            shuffle += 1;
+        }
+        iteration += 1;
+    }
+
+    println!("minimization complete");
+
+    for i in 0..aig.latches.len() {
+        let bit = if options.fixed_init || graph.required_inputs.contains(&input_id(None, i)) {
+            latch_init[i]
+        } else {
+            None
+        };
+
+        write_output_bit(writer, bit);
+    }
+
+    writer.write_all_defer_err(b"\n");
+
+    for (t, inputs) in frame_inputs.iter().enumerate() {
+        for i in 0..aig.input_count {
+            let bit = if graph.required_inputs.contains(&input_id(Some(t), i)) {
+                inputs[i]
+            } else {
+                None
+            };
+
+            write_output_bit(writer, bit);
+        }
+        writer.write_all_defer_err(b"\n");
+    }
+
+    writer.write_all_defer_err(b"# DONE\n");
+    writer.flush_defer_err();
+    writer.check_io_error()?;
+
+    let Some(verify) = options.verify else {
+        return Ok(());
+    };
+
+    let mut check_state: Vec<Option<bool>> = vec![];
+
+    let empty_set = BTreeSet::new();
+
+    let verify_from = match verify {
+        Verification::Cex => &empty_set,
+        Verification::Full => &graph.required_inputs,
+    };
+
+    for check in [None]
+        .into_iter()
+        .chain(verify_from.iter().copied().map(Some))
+    {
+        check_state.clear();
+
+        initial_frame(
+            aig,
+            &mut check_state,
+            |i, _| {
+                let input = input_id(None, i);
+                if options.fixed_init
+                    || (Some(input) != check && graph.required_inputs.contains(&input))
+                {
+                    latch_init[i]
+                } else {
+                    None
+                }
+            },
+            |i, _| {
+                let input = input_id(Some(0), i);
+                if Some(input) != check && graph.required_inputs.contains(&input) {
+                    initial_inputs[i]
+                } else {
+                    None
+                }
+            },
+            &mut (),
+        );
+
+        let mut bad_state = false;
+
+        'frame: for (t, inputs) in frame_inputs.iter().enumerate() {
+            if t > 0 {
+                successor_frame(
+                    aig,
+                    &mut check_state,
+                    |i, _| {
+                        let input = input_id(Some(t), i);
+                        if Some(input) != check && graph.required_inputs.contains(&input) {
+                            inputs[i]
+                        } else {
+                            None
+                        }
+                    },
+                    &mut (),
+                );
+            }
+
+            for bad in aig.bad_state_properties.iter() {
+                let (var, polarity) = unpack_lit(*bad);
+                let bad_output = check_state[var].invert_if(polarity, &mut ());
+                if bad_output == Some(true) {
+                    bad_state = true;
+                    break 'frame;
+                }
+            }
+        }
+
+        if bad_state != check.is_none() {
+            if let Some(check) = check {
+                let (frame, input) = decode_input_id(check);
+                if let Some(frame) = frame {
+                    bail!("minimality verification wrt. frame {frame} input {input} failed");
+                } else {
+                    bail!("minimality verification wrt. initial latch {input} failed");
+                }
+            } else {
+                bail!("counter example verification failed");
+            }
+        }
+
+        if let Some(check) = check {
+            let (frame, input) = decode_input_id(check);
+            if let Some(frame) = frame {
+                println!("verified minimality wrt. frame {frame} input {input}");
+            } else {
+                println!("verified minimality wrt. initial latch {input}");
+            }
+        } else {
+            println!("verified counter example");
+        }
+    }
+
+    Ok(())
+}

tools/aigcexmin/src/main.rs

@@ -0,0 +1,145 @@
+#![allow(clippy::needless_range_loop)]
+
+use std::{fs, mem::replace, path::PathBuf};
+
+use clap::{Parser, ValueEnum};
+use color_eyre::eyre::bail;
+
+use flussab_aiger::binary;
+
+pub mod aig_eval;
+pub mod care_graph;
+pub mod util;
+
+/// AIG counter example minimization
+#[derive(clap::Parser)]
+#[command(author, version, about, long_about = None, help_template="\
+{before-help}{name} {version}
+{author-with-newline}{about-with-newline}
+{usage-heading} {usage}
+
+{all-args}{after-help}
+")]
+pub struct Options {
+    /// Input AIGER file
+    aig: PathBuf,
+    /// Input AIGER witness file
+    witness: PathBuf,
+    /// Output AIGER witness file
+    output: PathBuf,
+
+    /// Verify the minimized counter example
+    #[clap(long, default_value = "cex")]
+    verify: VerificationOption,
+
+    /// Minimize latch initialization values
+    ///
+    /// Without this option the latch initialization values of the witness file are assumed to be
+    /// fixed and will remain as-is in the minimized witness file.
+    ///
+    /// Note that some tools (including the current Yosys/SBY flow) do not use AIGER native latch
+    /// initialization but instead perform initialization using inputs in the first frame.
+    #[clap(long)]
+    latches: bool,
+}
+
+#[derive(Copy, Clone, ValueEnum)]
+enum VerificationOption {
+    /// Skip verification
+    Off,
+    /// Verify the counter example
+    Cex,
+    /// Verify the counter example and that it is minimal (expensive)
+    Full,
+}
+
+fn main() -> color_eyre::Result<()> {
+    let options = Options::parse();
+
+    color_eyre::install()?;
+
+    let file_input = fs::File::open(options.aig)?;
+    let file_witness = fs::File::open(options.witness)?;
+    let file_output = fs::File::create(options.output)?;
+
+    let mut writer_output = flussab::DeferredWriter::from_write(file_output);
+
+    let mut read_witness_owned = flussab::DeferredReader::from_read(file_witness);
+    let read_witness = &mut read_witness_owned;
+
+    let aig_reader = binary::Parser::<u32>::from_read(file_input, binary::Config::default())?;
+
+    let aig = aig_reader.parse()?;
+
+    let mut offset = 0;
+    offset = flussab::text::next_newline(read_witness, offset);
+
+    if offset == 2 {
+        read_witness.advance(replace(&mut offset, 0));
+        offset = flussab::text::next_newline(read_witness, offset);
+        read_witness.advance(replace(&mut offset, 0));
+
+        offset = flussab::text::next_newline(read_witness, offset);
+    }
+
+    if offset != aig.latches.len() + 1 {
+        bail!(
+            "unexpected number of initial latch states, found {} expected {}",
+            offset.saturating_sub(1),
+            aig.latches.len()
+        );
+    }
+
+    let latch_init = read_witness.buf()[..aig.latches.len()]
+        .iter()
+        .copied()
+        .map(util::parse_input_bit)
+        .collect::<Result<Vec<_>, _>>()?;
+
+    read_witness.advance(replace(&mut offset, 0));
+
+    let mut frame_inputs = vec![];
+
+    loop {
+        offset = flussab::text::next_newline(read_witness, offset);
+
+        if matches!(read_witness.buf().first(), None | Some(b'.') | Some(b'#')) {
+            read_witness.check_io_error()?;
+            break;
+        }
+
+        if offset != aig.input_count + 1 {
+            bail!(
+                "unexpected number of input bits, found {} expected {}",
+                offset.saturating_sub(1),
+                aig.input_count
+            );
+        }
+
+        frame_inputs.push(
+            read_witness.buf()[..aig.input_count]
+                .iter()
+                .copied()
+                .map(util::parse_input_bit)
+                .collect::<Result<Vec<_>, _>>()?,
+        );
+        read_witness.advance(replace(&mut offset, 0));
+    }
+
+    care_graph::minimize(
+        &aig,
+        &latch_init,
+        &frame_inputs,
+        &mut writer_output,
+        &care_graph::MinimizationOptions {
+            fixed_init: !options.latches,
+            verify: match options.verify {
+                VerificationOption::Off => None,
+                VerificationOption::Cex => Some(care_graph::Verification::Cex),
+                VerificationOption::Full => Some(care_graph::Verification::Full),
+            },
+        },
+    )?;
+
+    Ok(())
+}

tools/aigcexmin/src/util.rs

@@ -0,0 +1,25 @@
+use color_eyre::eyre::bail;
+use flussab::DeferredWriter;
+use flussab_aiger::Lit;
+
+pub fn unpack_lit<L: Lit>(lit: L) -> (usize, bool) {
+    let lit = lit.code();
+    (lit >> 1, lit & 1 != 0)
+}
+
+pub fn parse_input_bit(byte: u8) -> color_eyre::Result<Option<bool>> {
+    Ok(match byte {
+        b'0' => Some(false),
+        b'1' => Some(true),
+        b'x' => None,
+        _ => bail!("unexpected input bit {byte:?}"),
+    })
+}
+
+pub fn write_output_bit(writer: &mut DeferredWriter, bit: Option<bool>) {
+    writer.write_all_defer_err(match bit {
+        Some(false) => b"0",
+        Some(true) => b"1",
+        None => b"x",
+    })
+}