SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

dualmaster-membridge

claude-code claude-opus-4-8 ✓ resolved GOOD_SUCCESS ↑ View task
Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.
Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.
Classification , post-hoc; cannot change the reward
GOOD_SUCCESSLegitimate solve, implements the asked-for behavior; tests verify real functionality.
SubtypeLegitimate Solution
EvidenceVerified result shows reward 1.0. Verifier output: "TEST dut_present: PASS", "TEST dut_forbidden: PASS", "TEST dut_compiles: PASS", "TEST simulation_completed: PASS (Mismatches: 0 in 3839 samples)", and "TEST reference_equivalence: PASS (all 3839 samples matched reference)". The agent trajectory shows it wrote /app/dut.sv from the prompt, compiled it with iverilog, and used only a self-created /tmp/tb.sv; there is no evidence of reading /tests, /solution, ref.sv, or fix.patch.
Root causeThe agent implemented a functional SystemVerilog TopModule matching the specified fixed-latency arbitration and fairness behavior. The verifier performed behavioral equivalence against the reference over broad stimulus and found zero mismatches.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
3 tool calls · 2 tool types · 8 steps
A bridge shares one read-only memory port between requesters A and B, keeping neither starved. Ports: clk, rst, a_req_i, a_addr_i (8), a_ack_o, a_data_o (16), b_req_i, b_addr_i (8), b_ack_o, b_data_o (16), m_req_o, m_addr_o (8), m_data_i (16). rst is synchronous active high, clearing all state and outputs to 0. All outputs are registered. A requester holds req and addr stable through the cycle after its ack. The bridge samples on the idle edge after a request first appears, calling that edge E; a freshly-arriving request is registered one idle cycle before it is sampled as E. One request finishes before the next is sampled. m_req_o and m_addr_o carry the chosen command during E+1 only. m_data_i is valid during E+3. The winner's ack and word are high during E+4 only, the other ack 0. E+4 is the last occupied cycle; the bridge is idle again at E+5, never earlier or later. A sample after a fully idle stretch favours A when both ask. The sample at E+5 directly after an operation instead takes the requester that did not just win if it asks, else the one that did; a later idle stretch resets this, so the next cold sample favours A again. edge E E+1 E+3 E+4 E+5 E+6 m_req_o 0 1 0 0 0 1 a_ack_o 0 0 0 1 0 0 a_data_o and b_data_o matter only while the matching ack is high. Write module TopModule to /app/dut.sv. Plain ASCII synthesizable SystemVerilog only: no define, include, ifdef, system tasks, force, release, bind.
Looking at this problem, I need to design a memory bridge arbiter with specific timing and fairness rules. Let me carefully work through the timing model before writing the code. Let me analyze the key timing facts: - Requests are registered one idle cycle before being sampled at E (input registration → gives cold-start a 1-cycle delay, but back-to-back re-sampling at E+5 is immediate since the register runs continuously) - Decision at cycle E → `m_req_o` at E+1 → data valid E+3 → ack at E+4 → idle at E+5 - Fairness: cold sample favors A; the immediate post-op sample (E+5) favors the *loser*, and a request-free idle cycle resets to "cold" Let me write the module:
write · /app/dut.sv
module TopModule (
    input  logic        clk,
    input  logic        rst,
    input  logic        a_req_i,
    input  logic [7:0]  a_addr_i,
    output logic        a_ack_o,
    output logic [15:0] a_data_o,
    input  logic        b_req_i,
    input  logic [7:0]  b_addr_i,
    output logic        b_ack_o,
    output logic [15:0] b_data_o,
    output logic        m_req_o,
    output logic [7:0]  m_addr_o,
    input  logic [15:0] m_data_i
);

    // FSM states (one busy pass = IDLE -> S1 -> S2 -> S3 -> S4 -> IDLE)
    localparam [2:0] IDLE = 3'd0,
                     S1   = 3'd1,  // cycle E+1 : m_req_o asserted
                     S2   = 3'd2,  // cycle E+2
                     S3   = 3'd3,  // cycle E+3 : m_data_i valid
                     S4   = 3'd4;   // cycle E+4 : winner ack + data

    logic [2:0] state;

    // continuously-registered request/address inputs
    logic       a_req_q, b_req_q;
    logic [7:0] a_addr_q, b_addr_q;

    // fairness state
    logic       hot;       // 1 => we are in the special sample right after an op
    logic       last_win;  // 0 = A won last, 1 = B won last

    // winner of the operation in flight (0 = A, 1 = B)
    logic       win;

    // combinational arbitration used while in IDLE
    logic       pending;
    logic       sel;

    always_comb begin
        pending = a_req_q | b_req_q;
        sel     = 1'b0;
        if (hot) begin
            // prefer the requester that did NOT just win
            if (last_win == 1'b0) begin
                // A won last -> prefer B, else fall back to A
                sel = b_req_q ? 1'b1 : 1'b0;
            end else begin
                // B won last -> prefer A, else fall back to B
                sel = a_req_q ? 1'b0 : 1'b1;
            end
        end else begin
            // cold sample -> favour A
            sel = a_req_q ? 1'b0 : 1'b1;
        end
    end

    always_ff @(posedge clk) begin
        if (rst) begin
            state    <= IDLE;
            a_req_q  <= 1'b0;
            b_req_q  <= 1'b0;
            a_addr_q <= 8'd0;
            b_addr_q <= 8'd0;
            hot      <= 1'b0;
            last_win <= 1'b0;
            win      <= 1'b0;
            a_ack_o  <= 1'b0;
            a_data_o <= 16'd0;
            b_ack_o  <= 1'b0;
            b_data_o <= 16'd0;
            m_req_o  <= 1'b0;
            m_addr_o <= 8'd0;
        end else begin
            // register incoming requests/addresses every cycle
            a_req_q  <= a_req_i;
            b_req_q  <= b_req_i;
            a_addr_q <= a_addr_i;
            b_addr_q <= b_addr_i;

            // default deassertions (single-cycle strobes)
            a_ack_o <= 1'b0;
            b_ack_o <= 1'b0;
            m_req_o <= 1'b0;

            case (state)
                IDLE: begin
                    if (pending) begin
                        // this cycle is E: launch the command for cycle E+1
                        win      <= sel;
                        m_req_o  <= 1'b1;
                        m_addr_o <= (sel == 1'b0) ? a_addr_q : b_addr_q;
                        state    <= S1;
                    end else begin
                        // a request-free idle cycle resets fairness to cold
                        hot   <= 1'b0;
                        state <= IDLE;
                    end
                end

                S1: state <= S2;

                S2: state <= S3;

                S3: begin
                    // m_data_i is valid this cycle; present winner ack+data next cycle
                    if (win == 1'b0) begin
                        a_data_o <= m_data_i;
                        a_ack_o  <= 1'b1;
                    end else begin
                        b_data_o <= m_data_i;
                        b_ack_o  <= 1'b1;
                    end
                    state <= S4;
                end

                S4: begin
                    // operation complete; next idle cycle is the special sample
                    hot      <= 1'b1;
                    last_win <= win;
                    state    <= IDLE;
                end

                default: state <= IDLE;
            endcase
        end
    end

endmodule
Let me verify it compiles cleanly if a SystemVerilog compiler is available:

Lint/compile the SystemVerilog module

shell
(command -v verilator >/dev/null 2>&1 && verilator --lint-only -Wall -Wno-DECLFILENAME dut.sv 2>&1 | head -40 || echo "verilator not found"); (command -v iverilog >/dev/null 2>&1 && iverilog -g2012 -o /tmp/dut.out dut.sv 2>&1 | head -40 && echo "iverilog OK" || echo "iverilog not found")
output
verilator not found
iverilog OK

[stdout]
verilator not found
iverilog OK
Compiles cleanly. Let me write a quick testbench to verify the timing waveform matches the spec:

Run timing testbench

shell
cat > /tmp/tb.sv <<'EOF'
module tb;
  logic clk=0, rst;
  logic a_req_i, b_req_i;
  logic [7:0] a_addr_i, b_addr_i, m_addr_o;
  logic a_ack_o, b_ack_o, m_req_o;
  logic [15:0] a_data_o, b_data_o, m_data_i;
  integer cyc=0;

  TopModule dut(.*);
  always #5 clk=~clk;

  // model memory: 2-cycle latency, data = addr*16 + 1
  logic [7:0] mem_addr_d1, mem_addr_d2;
  logic mem_v1, mem_v2;
  always @(posedge clk) begin
    mem_addr_d1 <= m_addr_o; mem_v1 <= m_req_o;
    mem_addr_d2 <= mem_addr_d1; mem_v2 <= mem_v1;
  end
  assign m_data_i = {mem_addr_d2, 8'h01};

  task step; begin @(posedge clk); #1; cyc=cyc+1;
    $display("cyc=%0d areq=%b breq=%b | m_req=%b m_addr=%0d | a_ack=%b a_data=%0d | b_ack=%b b_data=%0d",
      cyc, a_req_i, b_req_i, m_req_o, m_addr_o, a_ack_o, a_data_o, b_ack_o, b_data_o);
  end endtask

  initial begin
    rst=1; a_req_i=0; b_req_i=0; a_addr_i=8'h05; b_addr_i=8'h09;
    step; rst=0;
    $display("--- cold single A (req at cyc2) ---");
    step;                       // cyc2 idle
    a_req_i=1;                  // request appears
    step; step; step; step; step; step; step;  // observe
    a_req_i=0;
    step; step; step; step;
    $display("--- both A and B held continuously ---");
    a_req_i=1; b_req_i=1;
    repeat(16) step;
    $finish;
  end
endmodule
EOF
iverilog -g2012 -o /tmp/sim.out /app/dut.sv /tmp/tb.sv && vvp /tmp/sim.out
output
cyc=1 areq=0 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
--- cold single A (req at cyc2) ---
cyc=2 areq=0 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=3 areq=1 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=4 areq=1 breq=0 | m_req=1 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=5 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=6 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=7 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=8 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=9 areq=1 breq=0 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=10 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=11 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=12 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=13 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
--- both A and B held continuously ---
cyc=14 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=15 areq=1 breq=1 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=16 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=17 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=18 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=19 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=20 areq=1 breq=1 | m_req=1 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=21 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=22 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=23 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=1 b_data=2305
cyc=24 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=25 areq=1 breq=1 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=26 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=27 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=28 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=2305
cyc=29 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
/tmp/tb.sv:38: $finish called at 286 (1s)

[stdout]
cyc=1 areq=0 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
--- cold single A (req at cyc2) ---
cyc=2 areq=0 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=3 areq=1 breq=0 | m_req=0 m_addr=0 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=4 areq=1 breq=0 | m_req=1 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=5 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=6 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=0 | b_ack=0 b_data=0
cyc=7 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=8 areq=1 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=9 areq=1 breq=0 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=10 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=11 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=12 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=13 areq=0 breq=0 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
--- both A and B held continuously ---
cyc=14 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=15 areq=1 breq=1 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=16 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=17 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=18 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=0
cyc=19 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=20 areq=1 breq=1 | m_req=1 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=21 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=22 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=0
cyc=23 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=1 b_data=2305
cyc=24 areq=1 breq=1 | m_req=0 m_addr=9 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=25 areq=1 breq=1 | m_req=1 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=26 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=27 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
cyc=28 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=1 a_data=1281 | b_ack=0 b_data=2305
cyc=29 areq=1 breq=1 | m_req=0 m_addr=5 | a_ack=0 a_data=1281 | b_ack=0 b_data=2305
/tmp/tb.sv:38: $finish called at 286 (1s)
The waveform matches the specification exactly. Let me verify each spec requirement against the trace: **Cold single-A request** (raw req appears during cyc2, registered → sampled at E=cyc3): - `m_req_o=1`, `m_addr=5` at cyc4 = **E+1** ✓ - `a_ack_o=1`, `a_data=1281` (`0x0501` = addr 5) at cyc7 = **E+4**, single cycle ✓ - idle again at cyc8 = **E+5** ✓ - Registration delay present (raw→E is one idle cycle) ✓ **Fairness , both held continuously** (cold sample at cyc14): - Cold sample **favours A** → A wins first (addr 5) ✓ - Next sample at E+5 (cyc19) **takes the loser B** (addr 9, `b_data=2305`=`0x0901`) ✓ - Then back to A, then B... clean **alternation, neither starved** ✓ - Back-to-back re-sample is immediate: `m_req` at **E+6** with no wasted wait cycle ✓ **Idle-stretch reset**: after A's op finished with no pending request (cyc13), the "hot" preference cleared, so the next contested sample (cyc14) was cold and favoured A again ✓ **Other checks**: reset clears all outputs to 0 (cyc1) ✓; `m_req_o`/`m_addr_o` only during E+1 ✓; data captured from `m_data_i` (valid at E+3) and routed to the winner ✓; the other requester's ack stays 0 ✓. The module `/app/dut.sv` is complete , plain ASCII synthesizable SystemVerilog, all outputs registered, no `define`/`include`/`ifdef`/system-tasks/`force`/`release`/`bind`, and it compiles cleanly under iverilog (`-g2012`). The design works as follows: - **Input registration** (`a_req_q`/`b_req_q`/`a_addr_q`/`b_addr_q`) runs every cycle. This naturally gives cold starts a one-cycle delay before E, while back-to-back re-sampling at E+5 is immediate (the register is already tracking) , producing the required `m_req` at E+1 (cold) vs E+6 (chained). - A 5-state FSM (`IDLE→S1→S2→S3→S4→IDLE`) sequences the fixed latency: command at E+1, data capture at E+3, ack at E+4, idle at E+5. - **Fairness** uses `hot` (are we in the special post-op sample?) and `last_win`: cold → prefer A; hot → prefer the non-winner ("else the one that did"); a request-free idle cycle clears `hot` back to cold.
Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward
tests/test.sh
TEST dut_present: PASS (/app/dut.sv exists)
TEST dut_forbidden: PASS (no forbidden constructs)
TEST dut_compiles: PASS (compiled with held-back reference/testbench)
TEST simulation_completed: PASS (Mismatches: 0 in 3839 samples)
TEST reference_equivalence: PASS (all 3839 samples matched reference)
{"score": 1.000000, "results_file": "/tmp/h2t-grader-home.EcvBD9/runtime/cb_verifier_313-6827-9033-6823_313/results.jsonl"}

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_0aa87323bf934040. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_0aa87323bf934040 · verifier authoritative; classifier explanatory.