From 0c1737647b246d022ced64257905c581c0f8636e Mon Sep 17 00:00:00 2001
From: appellet <antoine.pelletier@epfl.ch>
Date: Sun, 25 May 2025 16:35:41 +0200
Subject: [PATCH] feat: get 67% correctness

---
 decoder.py     | 60 ++++++++++++++++++++-------------------------
 encoder.py     | 66 +++++++++++++++++++++++++++++++++++++++++---------
 test_local.py  | 43 +++++++++++++++++++++++---------
 test_server.py | 64 ++++++++++++++++++++++++++++++++++--------------
 4 files changed, 157 insertions(+), 76 deletions(-)

diff --git a/decoder.py b/decoder.py
index 3a82c04..75a0750 100644
--- a/decoder.py
+++ b/decoder.py
@@ -1,40 +1,32 @@
+# decoder.py
 import numpy as np
-from numpy import logaddexp
-from utils import index_to_char
-from codebook import construct_codebook
+from encoder import ALPHABET, G
 
-def decode_message(Y, codebook):
+
+def decode_blocks(Y: np.ndarray, C: np.ndarray) -> str:
     """
-    ML decoding for unknown channel state s:
-    p(Y|i) = 0.5*p(Y|i,s=1) + 0.5*p(Y|i,s=2)
-    We use log-sum-exp to combine both branch metrics.
+    Decode received samples by maximum correlation score
     """
-    G = 10
-    Y1, Y2 = Y[::2], Y[1::2]
-    best_idx = None
-    best_metric = -np.inf
-    for i, c in enumerate(codebook):
-        # Only consider indices that map to characters
-        if i not in index_to_char:
-            continue
-        c1, c2 = c[::2], c[1::2]
-        # Branch metrics (up to additive constants)
-        s1 = np.sqrt(G) * np.dot(Y1, c1) + np.dot(Y2, c2)
-        s2 = np.dot(Y1, c1) + np.sqrt(G) * np.dot(Y2, c2)
-        # Combine via log-sum-exp
-        metric = logaddexp(s1, s2)
-        if metric > best_metric:
-            best_metric = metric
-            best_idx = i
-    return best_idx
+    n = C.shape[1]
+    half = n // 2
+    num = Y.size // n
+    C1 = C[:, :half]
+    C2 = C[:, half:]
+    sqrtG = np.sqrt(G)
+    recovered = []
+    for k in range(num):
+        Yb = Y[k*n:(k+1)*n]
+        Ye, Yo = Yb[0::2], Yb[1::2]
+        s1 = sqrtG * (Ye @ C1.T) + (Yo @ C2.T)
+        s2 = (Ye @ C1.T) + sqrtG * (Yo @ C2.T)
+        score = np.maximum(s1, s2)
+        best = int(np.argmax(score))
+        recovered.append(ALPHABET[best])
+    return "".join(recovered)
 
 
-def signal_to_text(Y, codebook, r=6):
-    # Reconstruct codebook length (seg_len)
-    _, seg_len, _, _ = construct_codebook(r, 1)
-    text = ''
-    for i in range(40):
-        seg = Y[i * seg_len:(i + 1) * seg_len]
-        idx = decode_message(seg, codebook)
-        text += index_to_char.get(idx, '?')
-    return text
\ No newline at end of file
+def count_errors(orig: str, est: str):
+    """
+    List mismatches between orig and est
+    """
+    return [(i, o, e) for i, (o, e) in enumerate(zip(orig, est)) if o != e]
\ No newline at end of file
diff --git a/encoder.py b/encoder.py
index 92e81a8..de75bba 100644
--- a/encoder.py
+++ b/encoder.py
@@ -1,14 +1,56 @@
-# encoder.py (unchanged except default r)
+# encoder.py
 import numpy as np
-from codebook import construct_codebook
-from utils import char_to_index, normalize_energy
 
-def text_to_signal(text, r=5, Eb=3):
-    assert len(text) == 40, "Message must be exactly 40 characters."
-    codebook, n, m, alpha = construct_codebook(r, Eb)
-    # Map each character to its codeword
-    msg_indices = [char_to_index[c] for c in text]
-    signal = np.concatenate([codebook[i] for i in msg_indices])
-    # Enforce the energy constraint
-    signal = normalize_energy(signal, energy_limit=2000)
-    return signal, codebook
\ No newline at end of file
+# System parameters
+G = 10.0               # power gain for even samples
+ENERGY_LIMIT = 2000.0  # total energy per block
+ALPHABET = (
+    [chr(i) for i in range(ord('a'), ord('z')+1)] +
+    [chr(i) for i in range(ord('A'), ord('Z')+1)] +
+    [str(i) for i in range(10)] +
+    [' ', '.']
+)
+assert len(ALPHABET) == 64, "Alphabet must be size 64"
+
+
+def hadamard(r: int) -> np.ndarray:
+    if r == 0:
+        return np.array([[1]], dtype=float)
+    M = hadamard(r-1)
+    return np.block([[M, M], [M, -M]])
+
+
+def Br(r: int) -> np.ndarray:
+    M = hadamard(r)
+    return np.vstack([M, -M])
+
+
+def make_codebook(r: int, num_blocks: int) -> np.ndarray:
+    """
+    Build 64x64 codebook and scale blocks so energy per block ≤ ENERGY_LIMIT/num_blocks
+    """
+    B = Br(r)
+    C = np.hstack([B, B]).astype(float)
+    raw_norm = np.sum(C[0]**2)
+    margin = 0.95
+    alpha = margin * (ENERGY_LIMIT / num_blocks) / raw_norm
+    return np.sqrt(alpha) * C
+
+
+def interleave(c: np.ndarray) -> np.ndarray:
+    half = c.size // 2
+    x = np.empty(c.size)
+    x[0::2] = c[:half]
+    x[1::2] = c[half:]
+    return x
+
+
+def encode_message(msg: str, C: np.ndarray) -> np.ndarray:
+    """
+    Encode 40-character message into interleaved code symbols
+    """
+    if len(msg) != 40:
+        raise ValueError("Message must be exactly 40 characters.")
+    idx = [ALPHABET.index(ch) for ch in msg]
+    blocks = [interleave(C[i]) for i in idx]
+    return np.concatenate(blocks)
\ No newline at end of file
diff --git a/test_local.py b/test_local.py
index 23a6901..4495240 100644
--- a/test_local.py
+++ b/test_local.py
@@ -1,17 +1,36 @@
-from encoder import text_to_signal
-from decoder import signal_to_text
+# test_local.py
+#!/usr/bin/env python3
+import argparse
+import numpy as np
+from encoder import make_codebook, encode_message
+from decoder import decode_blocks, count_errors
 from channel import channel
 
-def test_local():
-    message = "HelloWorld123 ThisIsATestMessage12345678"
-    x, codebook = text_to_signal(message, r=6, Eb=3)
-    y = channel(x)
-    decoded = signal_to_text(y, codebook, r=6)
 
-    print(f"Original: {message}")
-    print(f"Decoded : {decoded}")
-    errors = sum(1 for a, b in zip(message, decoded) if a != b)
-    print(f"Character errors: {errors}/40")
+def main():
+    parser = argparse.ArgumentParser(description="Local test using channel.py")
+    parser.add_argument("--message", required=True, help="40-character message")
+    args = parser.parse_args()
+
+    msg = args.message
+    if len(msg) != 40:
+        raise ValueError("Message must be exactly 40 characters.")
+    C = make_codebook(r=5, num_blocks=len(msg))
+    x = encode_message(msg, C)
+    print(f"→ Total samples = {x.size}, total energy = {np.sum(x*x):.1f}")
+
+    Y = channel(x)
+
+    msg_hat = decode_blocks(Y, C)
+    print(f"↓ Decoded message: {msg_hat}")
+
+    errors = count_errors(msg, msg_hat)
+    print(f"Errors: {len(errors)} / {len(msg)} characters differ")
+    if errors:
+        for i, o, e in errors:
+            print(f"  Pos {i}: sent '{o}' but got '{e}'")
+    else:
+        print("✔️  No decoding errors!")
 
 if __name__ == "__main__":
-    test_local()
+    main()
diff --git a/test_server.py b/test_server.py
index bb4190f..9201646 100644
--- a/test_server.py
+++ b/test_server.py
@@ -1,28 +1,56 @@
+# test_server.py
+#!/usr/bin/env python3
+import argparse
 import subprocess
 import numpy as np
-from encoder import text_to_signal
-from decoder import signal_to_text
+from encoder import make_codebook, encode_message
+from decoder import decode_blocks, count_errors
 
-def test_server():
-    message = "HelloWorld123 ThisIsATestMessage12345678"
-    x, codebook = text_to_signal(message, r=6, Eb=3)
-    np.savetxt("input.txt", x, fmt="%.10f")
 
+def call_client(input_path, output_path, host, port):
     subprocess.run([
         "python3", "client.py",
-        "--input_file", "input.txt",
-        "--output_file", "output.txt",
-        "--srv_hostname", "iscsrv72.epfl.ch",
-        "--srv_port", "80"
-    ])
+        f"--input_file={input_path}",
+        f"--output_file={output_path}",
+        f"--srv_hostname={host}",
+        f"--srv_port={port}"
+    ], check=True)
 
-    y = np.loadtxt("output.txt")
-    decoded = signal_to_text(y, codebook, r=6)
 
-    print(f"Original: {message}")
-    print(f"Decoded : {decoded}")
-    errors = sum(1 for a, b in zip(message, decoded) if a != b)
-    print(f"Character errors: {errors}/40")
+def main():
+    parser = argparse.ArgumentParser(description="Server test using client.py")
+    parser.add_argument("--message", required=True, help="40-character message to send")
+    parser.add_argument("--srv_hostname", default="iscsrv72.epfl.ch", help="Server hostname")
+    parser.add_argument("--srv_port", type=int, default=80, help="Server port")
+    args = parser.parse_args()
+
+    msg = args.message
+    if len(msg) != 40:
+        raise ValueError("Message must be exactly 40 characters.")
+    C = make_codebook(r=5, num_blocks=len(msg))
+    x = encode_message(msg, C)
+
+    # write encoded symbols to fixed input.txt
+    input_file = "input.txt"
+    output_file = "output.txt"
+    np.savetxt(input_file, x)
+
+    # run client.py to read input.txt and write output.txt
+    call_client(input_file, output_file, args.srv_hostname, args.srv_port)
+
+    # read received samples
+    Y = np.loadtxt(output_file)
+
+    msg_hat = decode_blocks(Y, C)
+    print(f"↓ Decoded message: {msg_hat}")
+
+    errors = count_errors(msg, msg_hat)
+    print(f"Errors: {len(errors)} / {len(msg)} characters differ")
+    if errors:
+        for i, o, e in errors:
+            print(f"  Pos {i}: sent '{o}' but got '{e}'")
+    else:
+        print("✔️  No decoding errors!")
 
 if __name__ == "__main__":
-    test_server()
\ No newline at end of file
+    main()
\ No newline at end of file