SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

Serial bit-destuff framer

codex gpt-5.5 ✓ 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
EvidenceTest output shows 'INFO samples=672 dmiss=0 vmiss=0 fmiss=0 amiss=0' and 'ALL TESTS PASSED', with verifier outcome reward=1.0. Agent implemented working Verilog destuff logic that compiles with iverilog -g2012 and passes 672-sample test suite with zero mismatches. The implementation correctly handles: (1) emitting data bits, (2) removing stuffed bits after exactly 5 ones, (3) pulsing flag on 0 after exactly 6 ones, (4) pulsing abort on 7th consecutive 1, (5) holding state during stalls, (6) async active-low reset. Code shows lines 56-73 implementing the bit classification logic matching the instruction provided in trajectory step 3.
Root causeAgent successfully implemented the simplified serial bit-destuffer specification they received in the instruction, demonstrating solid SystemVerilog design, proper use of registered outputs, correct threshold comparisons, and appropriate state management. The implementation passes the provided test suite completely.
RecommendationN/A - task is fine. Note: The instruction provided to agent (trajectory step 3) is a simplified version that omits post-abort resync and the 'transparent stuffed bit' non-uniform run-count behavior mentioned in the original task.toml. If the full specification is intended, the instruction and tests need alignment with the complete requirements including: (1) stuffed bit leaves run unchanged at 5 (not reset to 0), (2) one-bit resync discarding the next bit after an abort, (3) full state-machine handling of all edge cases documented in the original instruction.md.
Trajectory
Tool-by-tool agent trajectory
13 tool calls · 2 tool types · 23 steps
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(file: /tmp/codex-home/skills/.system/skill-installer/SKILL.md) ### How to use skills - Discovery: The list above is the skills available in this session (name + description + source locator). `file` entries live on the host filesystem, `environment resource` entries are owned by their execution environment, `orchestrator resource` entries must be accessed through `skills.list` and `skills.read`, and `custom resource` entries use their provider's access mechanism. - Trigger rules: If the user names a skill (with `$SkillName` or plain text) OR the task clearly matches a skill's description shown above, you must use that skill for that turn. Multiple mentions mean use them all. 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# Serial bit-destuff framer ## Context We are receiving a serial bit stream one bit at a time and need the front-end block `bds` that cleans it up for the layer above. The transmitter on the far end inserts an extra `0` into the data whenever it has just sent a long-ish run of `1`s, so that the data can never accidentally look like one of the special delimiter patterns; our job is to take those inserted bits back out, hand the real data bits onward, and raise a side flag whenever a delimiter or an error-marker pattern goes by. The bit that makes this fiddly is that there is really only *one* piece of state here -- a running count of how many `1`s in a row we have just seen -- and that single count decides all of it at once: whether the next `0` is a real data bit or a bit to throw away, whether we just saw a delimiter, and whether we just saw an error marker. Get the count or its thresholds slightly off and every one of those decisions goes wrong together. The line is not always sending. On any cycle the count of incoming bits is qualified by a strobe; on the cycles where that strobe is low there is no bit to look at and the whole block has to sit still. The package and the wrapper are in place; only `rtl/bds.sv` is a stub. Implement it. ## Interface ``` input clk // single clock input rst_n // asynchronous, active low input s_in // serial data bit in input s_valid // input-bit strobe: s_in is a real bit only when high output d_out // recovered data bit out output d_valid // output-bit strobe: high for one clock per emitted bit output flag // delimiter-seen pulse output abort // error-marker-seen pulse ``` ## What "a bit arrives" means A bit arrives on a rising edge of `clk` where `s_valid` is high; `s_in` is that bit. On a rising edge where `s_valid` is low, **nothing happens**: `s_in` is meaningless, no bit is processed, the running count holds, `d_out` holds its last value, and `d_valid`, `flag` and `abort` are all low. The block only ever advances on cycles where a bit actually arrives. ## The running count Keep a count of how many `1` bits have arrived consecutively, **up to but not including the bit you are processing right now**. It starts at zero, and any `0` that you finish processing leaves it at zero. Everything below is phrased in terms of that count -- call it the *run* -- as it stands at the moment a bit arrives. ## Behaviour When a bit arrives (`s_valid` high), classify it by its value and by the run: - **A `1` bit.** If the run is already six -- i.e. this `1` is the *seventh* in a row -- it is an **error marker**: pulse `abort`, do not emit anything, and the run goes back to zero. Otherwise this `1` is a data bit: emit it (`d_out` = 1, `d_valid` high for this one cycle) and the run grows by one. - **A `0` bit.** Look at how many `1`s preceded it: - if the run is exactly **five**, this `0` is a **stuffed bit**: drop it -- emit nothing -- and the run goes back to zero; - if the run is exactly **six**, this `0` closes a **delimiter**: pulse `flag`, emit nothing, and the run goes back to zero; - otherwise (the run is four or fewer) this `0` is an ordinary data bit: emit it (`d_out` = 0, `d_valid` high for this one cycle) and the run goes back to zero. Note the thresholds are **exact counts, not "at least"**. A `0` only gets removed when precisely five `1`s came before it; a `0` after one, two, three or four `1`s is normal data and is emitted. The sixth `1` in a row is still a data bit that you emit; it is the *seventh* `1` that is the error marker. A `0` after six `1`s is a delimiter, not a removed bit. `d_valid`, `flag` and `abort` are each **one-clock pulses**: high only on the single cycle that processes the bit that caused them, low otherwise (and low on every stalled cycle). At most one of "`d_valid`", "`flag`" and "`abort`" is ever high on the same cycle. ## Precedence There is exactly one decision per arriving bit and it is fixed by `(value of the bit, run before it)`: a `1` is an abort when the run is six and data otherwise; a `0` is a removed stuff bit when the run is exactly five, a flag when the run is exactly six, and data otherwise. A bit that is dropped, that closes a flag, or that triggers an abort is never also emitted, and none of those bits advances the run -- they reset it to zero. ## Conventions `d_out`, `d_valid`, `flag` and `abort` are all **registered**: they take their new value on the rising edge that processes a bit and are observable from just after that edge until the next processed bit. The result of the bit that arrives on edge `E` lands on the outputs on that same edge `E` -- a single registered stage, no extra pipeline delay. `d_valid`, `flag` and `abort` are **pulses** (one clock each, as above), never levels. `d_out` is a held value: it changes only on a cycle that emits a bit and otherwise keeps whatever it last drove (its value is only meaningful on cycles where `d_valid` is high). `rst_n` is **asynchronous** and **active low**: while it is low the run count is cleared to zero and all four outputs are forced to zero, immediately on the falling edge of `rst_n` rather than waiting for a clock, and reset wins over `s_valid`. The run count holds across stalled (`s_valid` low) cycles, so a stall in the middle of a run of `1`s does not change which bit eventually trips the threshold. For an emitted bit on edge `E` with two stalled cycles after it: ``` edge E E+1 E+2 E+3 s_valid 1 0 0 1 d_valid 1 0 0 1 d_out A A A B ``` (`A` and `B` are the two emitted bits; across the stall `d_out` holds `A` and the run is unchanged.) ## Submission Write your implementation into `rtl/bds.sv`, keeping the module name, ports and parameters exactly as given. It must elaborate under Icarus Verilog 11 (`iverilog -g2012`); note that on that tool a bit- or part-select of an *expression* (a sum, a shift, a function result) is a syntax error, so keep the run count in a named register and do any such bit work inside a `function automatic` on a named value. The grader compiles your block with a held-back checker and compares `d_valid`, `flag` and `abort` every cycle, and `d_out` on the cycles you emit a bit, against a reference over directed and random stimulus.
I’ll inspect the existing wrapper/package and the stub so the implementation matches the repo’s style and exact module signature.
shell
pwd && rg --files
output
Chunk ID: 722da5
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 19
Output:
/work
bds_core/rtl/bds.sv
bds_core/rtl/bds_top.sv
bds_core/rtl/bds_pkg.sv
shell
git status --short
output
Chunk ID: cde2f3
Wall time: 0.0000 seconds
Process exited with code 127
Original token count: 11
Output:
/bin/bash: line 1: git: command not found
The repo is small and there is no `git` binary in this environment, so I’ll work directly against the files under `/work/bds_core`. Next I’m reading the package, wrapper, and stub before editing.
shell
sed -n '1,220p' rtl/bds.sv
output
Chunk ID: e0bd9b
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 709
Output:
//==============================================================================
// bds.sv
//
// Serial bit-destuff framer.
//
// ---------------------------------------------------------------------------
//  >>> IMPLEMENTATION REQUIRED <<<
//
//  The module ports, parameters and the run-count register are provided. The
//  destuff / flag / abort decode and the outputs are left as a TODO and
//  currently drive constant zeros, so the block emits nothing and the verifier
//  FAILS.
//
//  Implement the behaviour described in instruction.md. Do NOT change the module
//  name, the port list, or the parameter list.
//
//  iverilog 11 note: a bit/part-select of an EXPRESSION (a sum, a shift, a
//  function-call result) is a syntax error under `iverilog -g2012`. Index only
//  named signals, and do any bit work that needs an intermediate value inside a
//  `function automatic` using named locals. Keep the run count in a named
//  register.
// ---------------------------------------------------------------------------
//==============================================================================
`timescale 1ns/1ps

module bds #(
    parameter RUN_W   = 3,
    parameter STUFF_R = 5,
    parameter FLAG_R  = 6,
    parameter ABORT_R = 6
) (
    input  logic clk,
    input  logic rst_n,
    input  logic s_in,
    input  logic s_valid,
    output logic d_out,
    output logic d_valid,
    output logic flag,
    output logic abort
);

  // ---------------------------------------------------------------------------
  // State (provided): running count of consecutive 1 bits seen on the input
  // stream, BEFORE the bit currently being processed.
  // ---------------------------------------------------------------------------
  logic [RUN_W-1:0] run;

  // ===========================================================================
  // TODO: IMPLEMENT THE FRAMER.
  //   * process s_in only on cycles where s_valid is high; freeze every register
  //     (the run count and the outputs) on a stall;
  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
  //     detect flags, and detect aborts;
  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
  //   * asynchronous active-low reset clears the run count and all outputs.
  //
  // The placeholder below keeps the module compilable but INCORRECT.
  // ===========================================================================
  always_ff @(posedge clk or negedge rst_n) begin
    if (!rst_n) begin
      run <= '0;
    end else begin
      // TODO: replace with the real decode + control.
      run <= run;
    end
  end

  // TODO: replace these placeholder outputs with the real ones.
  assign d_out   = 1'b0;
  assign d_valid = 1'b0;
  assign flag    = 1'b0;
  assign abort   = 1'b0;

endmodule : bds
shell
sed -n '1,220p' rtl/bds_top.sv
output
Chunk ID: 11be42
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 269
Output:
//==============================================================================
// bds_top.sv
//
// Thin integration wrapper. The verification environment drives this wrapper so
// that the instantiation wiring is exercised alongside the destuff framer
// itself. It instantiates bds with the project-default geometry from bds_pkg.
//
// DO NOT change this file.
//==============================================================================
`timescale 1ns/1ps
`include "bds_pkg.sv"

module bds_top (
    input  logic clk,
    input  logic rst_n,
    input  logic s_in,
    input  logic s_valid,
    output logic d_out,
    output logic d_valid,
    output logic flag,
    output logic abort
);

  // Bare instantiation: the framer carries its own default geometry, so a
  // submission needs no parameter override to elaborate correctly.
  bds u_bds (
      .clk     (clk),
      .rst_n   (rst_n),
      .s_in    (s_in),
      .s_valid (s_valid),
      .d_out   (d_out),
      .d_valid (d_valid),
      .flag    (flag),
      .abort   (abort)
  );

endmodule : bds_top
shell
sed -n '1,220p' rtl/bds_pkg.sv
output
Chunk ID: 03adf6
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 381
Output:
//==============================================================================
// bds_pkg.sv
//
// Shared constants for the serial bit-destuff framer. The receiver keeps a small
// running count of consecutive 1 bits seen on the input stream; that one count
// drives stuff-bit removal, flag detection, abort detection and the output
// strobe together. The threshold constants live here so the data path and the
// integration wrapper agree on the geometry.
//
// Parameters are declared without an explicit data type for broad simulator
// compatibility (Icarus Verilog 11); they default to plain integer constants,
// which is sufficient here.
//
// DO NOT change this file.
//==============================================================================
`ifndef BDS_PKG_SV
`define BDS_PKG_SV

package bds_pkg;

  // Width of the consecutive-1 run counter. It only ever needs to represent the
  // values 0..6 (a seventh consecutive 1 is consumed as an abort and resets the
  // count), so three bits is ample.
  localparam RUN_W   = 3;

  // Run-length landmarks the contract keys off (counts of consecutive 1 bits
  // already seen, i.e. the run value BEFORE the bit currently being processed).
  localparam STUFF_R = 5;   // a 0 seen with exactly this many 1s before it is a stuffed bit
  localparam FLAG_R  = 6;   // a 0 seen with exactly this many 1s before it closes a flag
  localparam ABORT_R = 6;   // a 1 seen with this many 1s before it is the seventh 1 -> abort

endpackage : bds_pkg

`endif // BDS_PKG_SV
I found the intended `run` register already declared in the stub. I’m replacing the placeholder with a single clocked decode block so `run` and all outputs update together on arriving bits, while stalls only clear the pulse outputs and hold `d_out`/`run`.
apply_patch
*** Begin Patch
*** Update File: /work/bds_core/rtl/bds.sv
@@
-  // ===========================================================================
-  // TODO: IMPLEMENT THE FRAMER.
-  //   * process s_in only on cycles where s_valid is high; freeze every register
-  //     (the run count and the outputs) on a stall;
-  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
-  //     detect flags, and detect aborts;
-  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
-  //   * asynchronous active-low reset clears the run count and all outputs.
-  //
-  // The placeholder below keeps the module compilable but INCORRECT.
-  // ===========================================================================
   always_ff @(posedge clk or negedge rst_n) begin
     if (!rst_n) begin
-      run <= '0;
+      run     <= '0;
+      d_out   <= 1'b0;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
     end else begin
-      // TODO: replace with the real decode + control.
-      run <= run;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
+
+      if (s_valid) begin
+        if (s_in) begin
+          if (run == ABORT_R[RUN_W-1:0]) begin
+            abort <= 1'b1;
+            run   <= '0;
+          end else begin
+            d_out   <= 1'b1;
+            d_valid <= 1'b1;
+            run     <= run + {{(RUN_W-1){1'b0}}, 1'b1};
+          end
+        end else begin
+          if (run == STUFF_R[RUN_W-1:0]) begin
+            run <= '0;
+          end else if (run == FLAG_R[RUN_W-1:0]) begin
+            flag <= 1'b1;
+            run  <= '0;
+          end else begin
+            d_out   <= 1'b0;
+            d_valid <= 1'b1;
+            run     <= '0;
+          end
+        end
       end
     end
   end
-
-  // TODO: replace these placeholder outputs with the real ones.
-  assign d_out   = 1'b0;
-  assign d_valid = 1'b0;
-  assign flag    = 1'b0;
-  assign abort   = 1'b0;
 
 endmodule : bds
*** End Patch


apply_patch verification failed: Failed to find expected lines in /work/bds_core/rtl/bds.sv:
  // ===========================================================================
  // TODO: IMPLEMENT THE FRAMER.
  //   * process s_in only on cycles where s_valid is high; freeze every register
  //     (the run count and the outputs) on a stall;
  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
  //     detect flags, and detect aborts;
  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
  //   * asynchronous active-low reset clears the run count and all outputs.
  //
  // The placeholder below keeps the module compilable but INCORRECT.
  // ===========================================================================
  always_ff @(posedge clk or negedge rst_n) begin
    if (!rst_n) begin
      run <= '0;
    end else begin
      // TODO: replace with the real decode + control.
      run <= run;
      end
    end
  end

  // TODO: replace these placeholder outputs with the real ones.
  assign d_out   = 1'b0;
  assign d_valid = 1'b0;
  assign flag    = 1'b0;
  assign abort   = 1'b0;

endmodule : bds
The first patch missed the exact local text in the file, so I’m narrowing the edit to the clocked block and the placeholder assigns.
shell
nl -ba rtl/bds.sv | sed -n '35,95p'
output
Chunk ID: 33b0ec
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 448
Output:
    35	    input  logic s_valid,
    36	    output logic d_out,
    37	    output logic d_valid,
    38	    output logic flag,
    39	    output logic abort
    40	);
    41	
    42	  // ---------------------------------------------------------------------------
    43	  // State (provided): running count of consecutive 1 bits seen on the input
    44	  // stream, BEFORE the bit currently being processed.
    45	  // ---------------------------------------------------------------------------
    46	  logic [RUN_W-1:0] run;
    47	
    48	  // ===========================================================================
    49	  // TODO: IMPLEMENT THE FRAMER.
    50	  //   * process s_in only on cycles where s_valid is high; freeze every register
    51	  //     (the run count and the outputs) on a stall;
    52	  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
    53	  //     detect flags, and detect aborts;
    54	  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
    55	  //   * asynchronous active-low reset clears the run count and all outputs.
    56	  //
    57	  // The placeholder below keeps the module compilable but INCORRECT.
    58	  // ===========================================================================
    59	  always_ff @(posedge clk or negedge rst_n) begin
    60	    if (!rst_n) begin
    61	      run <= '0;
    62	    end else begin
    63	      // TODO: replace with the real decode + control.
    64	      run <= run;
    65	    end
    66	  end
    67	
    68	  // TODO: replace these placeholder outputs with the real ones.
    69	  assign d_out   = 1'b0;
    70	  assign d_valid = 1'b0;
    71	  assign flag    = 1'b0;
    72	  assign abort   = 1'b0;
    73	
    74	endmodule : bds
apply_patch
*** Begin Patch
*** Update File: /work/bds_core/rtl/bds.sv
@@
-  // ===========================================================================
-  // TODO: IMPLEMENT THE FRAMER.
-  //   * process s_in only on cycles where s_valid is high; freeze every register
-  //     (the run count and the outputs) on a stall;
-  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
-  //     detect flags, and detect aborts;
-  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
-  //   * asynchronous active-low reset clears the run count and all outputs.
-  //
-  // The placeholder below keeps the module compilable but INCORRECT.
-  // ===========================================================================
   always_ff @(posedge clk or negedge rst_n) begin
     if (!rst_n) begin
-      run <= '0;
+      run     <= '0;
+      d_out   <= 1'b0;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
     end else begin
-      // TODO: replace with the real decode + control.
-      run <= run;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
+
+      if (s_valid) begin
+        if (s_in) begin
+          if (run == ABORT_R[RUN_W-1:0]) begin
+            abort <= 1'b1;
+            run   <= '0;
+          end else begin
+            d_out   <= 1'b1;
+            d_valid <= 1'b1;
+            run     <= run + {{(RUN_W-1){1'b0}}, 1'b1};
+          end
+        end else begin
+          if (run == STUFF_R[RUN_W-1:0]) begin
+            run <= '0;
+          end else if (run == FLAG_R[RUN_W-1:0]) begin
+            flag <= 1'b1;
+            run  <= '0;
+          end else begin
+            d_out   <= 1'b0;
+            d_valid <= 1'b1;
+            run     <= '0;
+          end
+        end
+      end
     end
   end
-
-  // TODO: replace these placeholder outputs with the real ones.
-  assign d_out   = 1'b0;
-  assign d_valid = 1'b0;
-  assign flag    = 1'b0;
-  assign abort   = 1'b0;
 
 endmodule : bds
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
M /work/bds_core/rtl/bds.sv
The implementation is in place. I’m compiling it with `iverilog -g2012` now; if Icarus dislikes any SystemVerilog sizing detail, I’ll adjust to its parser rather than relying on a simulator-specific extension.
shell
iverilog -g2012 -o /tmp/bds_compile.vvp rtl/bds_pkg.sv rtl/bds.sv rtl/bds_top.sv
output
Chunk ID: 212f22
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 14
Output:
rtl/bds_top.sv:12: Include file bds_pkg.sv not found
shell
iverilog -g2012 -I rtl -o /tmp/bds_compile.vvp rtl/bds_pkg.sv rtl/bds.sv rtl/bds_top.sv
output
Chunk ID: fa0afc
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
Compilation succeeds once the wrapper include path is provided. I’m doing a small cleanup pass now to remove the stale stub comments and simplify the threshold comparisons so the source is clearer under Icarus.
apply_patch
*** Begin Patch
*** Update File: /work/bds_core/rtl/bds.sv
@@
-//  >>> IMPLEMENTATION REQUIRED <<<
-//
-//  The module ports, parameters and the run-count register are provided. The
-//  destuff / flag / abort decode and the outputs are left as a TODO and
-//  currently drive constant zeros, so the block emits nothing and the verifier
-//  FAILS.
-//
-//  Implement the behaviour described in instruction.md. Do NOT change the module
-//  name, the port list, or the parameter list.
+//  The module ports, parameters and run-count register are fixed by the project
+//  harness. The implementation below emits data bits, removes stuffed bits, and
+//  pulses flag / abort from the run count before the arriving bit.
@@
-          if (run == ABORT_R[RUN_W-1:0]) begin
+          if (run == ABORT_R) begin
             abort <= 1'b1;
             run   <= '0;
           end else begin
             d_out   <= 1'b1;
             d_valid <= 1'b1;
-            run     <= run + {{(RUN_W-1){1'b0}}, 1'b1};
+            run     <= run + 1'b1;
           end
         end else begin
-          if (run == STUFF_R[RUN_W-1:0]) begin
+          if (run == STUFF_R) begin
             run <= '0;
-          end else if (run == FLAG_R[RUN_W-1:0]) begin
+          end else if (run == FLAG_R) begin
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
M /work/bds_core/rtl/bds.sv
shell
iverilog -g2012 -I rtl -o /tmp/bds_compile.vvp rtl/bds_pkg.sv rtl/bds.sv rtl/bds_top.sv
output
Chunk ID: 3d0aef
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
shell
nl -ba rtl/bds.sv | sed -n '1,130p'
output
Chunk ID: 3a280b
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 761
Output:
     1	//==============================================================================
     2	// bds.sv
     3	//
     4	// Serial bit-destuff framer.
     5	//
     6	// ---------------------------------------------------------------------------
     7	//  The module ports, parameters and run-count register are fixed by the project
     8	//  harness. The implementation below emits data bits, removes stuffed bits, and
     9	//  pulses flag / abort from the run count before the arriving bit.
    10	//
    11	//  iverilog 11 note: a bit/part-select of an EXPRESSION (a sum, a shift, a
    12	//  function-call result) is a syntax error under `iverilog -g2012`. Index only
    13	//  named signals, and do any bit work that needs an intermediate value inside a
    14	//  `function automatic` using named locals. Keep the run count in a named
    15	//  register.
    16	// ---------------------------------------------------------------------------
    17	//==============================================================================
    18	`timescale 1ns/1ps
    19	
    20	module bds #(
    21	    parameter RUN_W   = 3,
    22	    parameter STUFF_R = 5,
    23	    parameter FLAG_R  = 6,
    24	    parameter ABORT_R = 6
    25	) (
    26	    input  logic clk,
    27	    input  logic rst_n,
    28	    input  logic s_in,
    29	    input  logic s_valid,
    30	    output logic d_out,
    31	    output logic d_valid,
    32	    output logic flag,
    33	    output logic abort
    34	);
    35	
    36	  // ---------------------------------------------------------------------------
    37	  // State (provided): running count of consecutive 1 bits seen on the input
    38	  // stream, BEFORE the bit currently being processed.
    39	  // ---------------------------------------------------------------------------
    40	  logic [RUN_W-1:0] run;
    41	
    42	  always_ff @(posedge clk or negedge rst_n) begin
    43	    if (!rst_n) begin
    44	      run     <= '0;
    45	      d_out   <= 1'b0;
    46	      d_valid <= 1'b0;
    47	      flag    <= 1'b0;
    48	      abort   <= 1'b0;
    49	    end else begin
    50	      d_valid <= 1'b0;
    51	      flag    <= 1'b0;
    52	      abort   <= 1'b0;
    53	
    54	      if (s_valid) begin
    55	        if (s_in) begin
    56	          if (run == ABORT_R) begin
    57	            abort <= 1'b1;
    58	            run   <= '0;
    59	          end else begin
    60	            d_out   <= 1'b1;
    61	            d_valid <= 1'b1;
    62	            run     <= run + 1'b1;
    63	          end
    64	        end else begin
    65	          if (run == STUFF_R) begin
    66	            run <= '0;
    67	          end else if (run == FLAG_R) begin
    68	            flag <= 1'b1;
    69	            run  <= '0;
    70	          end else begin
    71	            d_out   <= 1'b0;
    72	            d_valid <= 1'b1;
    73	            run     <= '0;
    74	          end
    75	        end
    76	      end
    77	    end
    78	  end
    79	
    80	endmodule : bds
Implemented `rtl/bds.sv` with the registered run-count decoder, including: - stuffed `0` removal after exactly five `1`s - delimiter `flag` after exactly six `1`s then `0` - `abort` on the seventh consecutive `1` - stalled-cycle behavior: `run`/`d_out` hold, pulse outputs clear - async active-low reset clearing state and outputs Verified compile with: ```sh iverilog -g2012 -I rtl -o /tmp/bds_compile.vvp rtl/bds_pkg.sv rtl/bds.sv rtl/bds_top.sv ``` No compile errors.
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.sh: compiling with iverilog...
----- iverilog output -----
---------------------------
test.sh: running simulation with vvp...
----- simulation output -----
INFO samples=672 dmiss=0 vmiss=0 fmiss=0 amiss=0
SAMPLES=672
ALL TESTS PASSED
-----------------------------
test.sh: PASS - 672 samples, no mismatches

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_ec43627b4e72444b. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_ec43627b4e72444b · verifier authoritative; classifier explanatory.