agentic-kvc/microbench/plot_interference.py

#!/usr/bin/env python3
"""
Plot prefill-decode interference results (Microbench 1).

Reads interference/results/summary.csv and produces two figures:

1. fig_interference_heatmap.png
     Heatmap of TPOT p90 interference index (during/baseline) over (D, P).

2. fig_interference_lines.png
     Two-panel: TPOT p90 during prefill (absolute, log) and prefill TTFT,
     one line per decode batch size D, x-axis = prefill tokens P.
"""

import csv
from collections import defaultdict
from pathlib import Path

import numpy as np
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt

HERE = Path(__file__).parent
CSV  = HERE / "interference/results/summary.csv"
OUT_DIR = HERE / "interference/results"
OUT_DIR.mkdir(parents=True, exist_ok=True)

# ── load + aggregate (median across reps) ────────────────────────────────────
rows = list(csv.DictReader(open(CSV)))

agg = defaultdict(list)
for r in rows:
    D = int(r["decode_batch_size"])
    P = int(r["new_prefill_tokens"])
    if D == 0:
        continue
    bl_p90  = float(r["tpot_baseline_p90_ms"])
    bl_p50  = float(r["tpot_baseline_p50_ms"])
    dur_p90 = float(r["tpot_during_prefill_p90_ms"])
    dur_p50 = float(r["tpot_during_prefill_p50_ms"])
    ttft    = float(r["prefill_ttft_ms"])
    if bl_p90 <= 0 or dur_p90 <= 0:
        continue
    agg[(D, P)].append({
        "bl_p50": bl_p50, "bl_p90": bl_p90,
        "dur_p50": dur_p50, "dur_p90": dur_p90,
        "ttft": ttft,
        "idx_p90": dur_p90 / bl_p90,
        "idx_p50": dur_p50 / bl_p50 if bl_p50 > 0 else 0,
    })

stat = {k: {kk: float(np.median([e[kk] for e in v])) for kk in v[0]} for k, v in agg.items()}

D_VALUES = sorted({k[0] for k in stat})
P_VALUES = sorted({k[1] for k in stat})

# ── Figure 1: heatmap of interference index (TPOT p90 during / baseline) ─────
mat = np.full((len(D_VALUES), len(P_VALUES)), np.nan)
for i, D in enumerate(D_VALUES):
    for j, P in enumerate(P_VALUES):
        s = stat.get((D, P))
        if s:
            mat[i, j] = s["idx_p90"]

fig, ax = plt.subplots(figsize=(9.5, 5))
im = ax.imshow(mat, cmap="YlOrRd", aspect="auto",
               norm=matplotlib.colors.LogNorm(vmin=1, vmax=mat[~np.isnan(mat)].max()))

ax.set_xticks(range(len(P_VALUES)))
ax.set_xticklabels([f"{P//1024}k" for P in P_VALUES], fontsize=11)
ax.set_yticks(range(len(D_VALUES)))
ax.set_yticklabels([f"D={D}" for D in D_VALUES], fontsize=11)
ax.set_xlabel("Cold prefill size  (P tokens)", fontsize=12)
ax.set_ylabel("Decode batch size", fontsize=12)
ax.set_title("Prefill-Decode Interference Index\n"
             "TPOT p90 during prefill / TPOT p90 baseline   (log color)",
             fontsize=13, fontweight="bold")

# annotate each cell
for i in range(len(D_VALUES)):
    for j in range(len(P_VALUES)):
        v = mat[i, j]
        if not np.isnan(v):
            txt_color = "white" if v > 50 else "black"
            ax.text(j, i, f"{v:.0f}x",
                    ha="center", va="center",
                    fontsize=10, color=txt_color, fontweight="bold")

cbar = plt.colorbar(im, ax=ax, fraction=0.04, pad=0.02)
cbar.set_label("Interference index  (×)", fontsize=10)

plt.tight_layout()
out_heatmap = OUT_DIR / "fig_interference_heatmap.png"
plt.savefig(out_heatmap, dpi=160, bbox_inches="tight")
print(f"Saved: {out_heatmap}")
plt.close(fig)

# ── Figure 2: lines, two panels ──────────────────────────────────────────────
fig, axes = plt.subplots(1, 2, figsize=(13, 5))

D_COLORS = {1: "#1f77b4", 2: "#2ca02c", 4: "#ff7f0e", 8: "#d62728"}

# Panel A: TPOT p90 during prefill (absolute, log y)
ax = axes[0]
for D in D_VALUES:
    ys_dur = [stat.get((D, P), {}).get("dur_p90", np.nan) for P in P_VALUES]
    ys_bl  = [stat.get((D, P), {}).get("bl_p90",  np.nan) for P in P_VALUES]
    color = D_COLORS.get(D, "gray")
    ax.plot(P_VALUES, ys_dur, "o-", color=color, label=f"D={D} (during prefill)",
            linewidth=2, markersize=7)
    ax.plot(P_VALUES, ys_bl, "s--", color=color, alpha=0.4,
            label=f"D={D} (baseline)", linewidth=1, markersize=5)

ax.set_xscale("log", base=2)
ax.set_yscale("log")
ax.set_xticks(P_VALUES)
ax.set_xticklabels([f"{P//1024}k" for P in P_VALUES])
ax.set_xlabel("Cold prefill size  (P tokens)", fontsize=12)
ax.set_ylabel("TPOT p90  (ms, log)", fontsize=12)
ax.set_title("Decode TPOT during prefill chunk", fontsize=12, fontweight="bold")
ax.grid(True, which="both", linestyle="--", alpha=0.4)
ax.legend(fontsize=8, loc="upper left", ncol=2)

# Panel B: prefill TTFT vs P
ax = axes[1]
for D in D_VALUES:
    ys = [stat.get((D, P), {}).get("ttft", np.nan) for P in P_VALUES]
    color = D_COLORS.get(D, "gray")
    ax.plot(P_VALUES, ys, "o-", color=color, label=f"D={D}",
            linewidth=2, markersize=7)

ax.set_xscale("log", base=2)
ax.set_xticks(P_VALUES)
ax.set_xticklabels([f"{P//1024}k" for P in P_VALUES])
ax.set_xlabel("Cold prefill size  (P tokens)", fontsize=12)
ax.set_ylabel("Prefill TTFT  (ms)", fontsize=12)
ax.set_title("Cold prefill duration  (interference window length)",
             fontsize=12, fontweight="bold")
ax.grid(True, linestyle="--", alpha=0.4)
ax.legend(fontsize=9, loc="upper left", title="Decode batch")

fig.suptitle(
    "Prefill-Decode Interference  ·  Qwen3-Coder-30B-A3B  ·  H20  ·  chunk_size=8192",
    fontsize=13, fontweight="bold", y=1.02)

plt.tight_layout()
out_lines = OUT_DIR / "fig_interference_lines.png"
plt.savefig(out_lines, dpi=160, bbox_inches="tight")
print(f"Saved: {out_lines}")
plt.close(fig)

# ── print summary table ──────────────────────────────────────────────────────
print(f"\n{'D':>3} {'P':>6} | {'bl_p90':>7} {'dur_p90':>8} {'idx_p90':>7} | {'ttft':>7}")
print("-" * 55)
for (D, P) in sorted(stat.keys()):
    s = stat[(D, P)]
    print(f"{D:>3} {P:>6} | {s['bl_p90']:>6.2f}  {s['dur_p90']:>7.1f}  {s['idx_p90']:>5.1f}x  | {s['ttft']:>6.0f}")