Optimizer

Optimizer

What this is

A black-box optimization framework. You give it:

• A set of parameters with bounds (e.g. transistor widths, bias currents, resistor values)
• An evaluation function that takes parameters and returns performance metrics
• An objective that combines metrics into a single scalar to minimize

The optimizer iteratively picks parameter values, evaluates them, and converges toward the optimum. It treats the evaluation as a black box — it doesn't need to know whether you're running Spectre, Maestro, a Python model, or anything else.

When to use

• Circuit sizing — find W/L, bias currents, passive values that meet gain/BW/noise/power specs
• Design space exploration — sweep a high-dimensional parameter space that's too large for manual tuning or parametric sweeps
• Multi-objective tradeoffs — minimize power-delay product, noise-power FOM, etc.
• Any expensive black-box function — the evaluation can be slow (seconds to minutes per point); TuRBO is sample-efficient

When NOT to use

• Single-variable sweep — just use a parametric sweep in Maestro or a for-loop
• Analytical solution exists — if you can derive the optimum, don't search for it
• < 5 evaluations budget — TuRBO needs at least 2 * n_params initial samples

Algorithm choice

Prerequisites

• For TuRBO: pip install torch gpytorch and local TuRBO install (pip install -e TuRBO/)
  • TuRBO (Trust Region Bayesian Optimization) comes from uber-research/TuRBO
• For scipy: included in standard Python scientific stack

Core pattern

import numpy as np
from turbo import Turbo1

# 1. Define parameters and bounds
PARAMS = ["W_tail", "W_inp", "R_load"]
LB = np.array([0.5, 0.5, 100.])
UB = np.array([10., 10., 5000.])

# 2. Objective: params → scalar (minimize)
def objective(x):
    try:
        result = evaluate(x, PARAMS)
    except Exception:
        return 1e6                     # penalty on failure, never nan/inf
    return compute_metric(result)

# 3. Run
turbo = Turbo1(f=objective, lb=LB, ub=UB,
               n_init=2*len(LB), max_evals=100, batch_size=1)
turbo.optimize()
best = turbo.X[turbo.fX.argmin()]

Evaluation backends

The evaluate() function is the only part that changes between use cases:

Spectre netlist — parameterize a .scs template and run remotely:

from virtuoso_bridge.spectre.runner import SpectreSimulator
sim = SpectreSimulator.from_env(work_dir="./opt", output_format="psfascii")

def evaluate(x, params):
    text = Path("tb_template.scs").read_text()
    for name, val in zip(params, x):
        text = text.replace(f"@@{name}@@", f"{val:.6g}")
    Path("opt/tb.scs").write_text(text)
    return sim.run_simulation(Path("opt/tb.scs"), {})

Maestro — set design variables and run an existing test via SKILL:

from virtuoso_bridge import ramic_send

def evaluate(x, params):
    for name, val in zip(params, x):
        ramic_send(f'maeSetDesignVar("{name}" {val:.6g})')
    ramic_send('maeRunTest("myTest")')
    gain = float(ramic_send('maeGetTestResult("myTest" "gain_db")'))
    bw = float(ramic_send('maeGetTestResult("myTest" "bw_hz")'))
    return {"gain": gain, "bw": bw}

Any Python callable:

def evaluate(x, params):
    return my_model.predict(dict(zip(params, x)))

Packaged IC optimization workflow — use an external CLI when the task is larger than a single black-box function and already has a project convention:

• multiple Maestro/ADE point roots or testbenches must be aggregated
• scalar metrics should be evaluated by existing OCEAN/SKILL expressions, not reimplemented in Python
• design variables are discrete, quantized, or constrained by legal grids
• runs need durable artifacts: requirement files, reports, plots, manifests, continuation state, and structured failure diagnostics

In that case, keep virtuoso-bridge-lite as the Cadence access layer and call the workflow CLI from the evaluation backend rather than vendoring it into this skill. For example, HAIDERZz/IC-opt-workflow uses an opt_requirement.md project folder, Spectre/OCEAN metric extraction, OpenBox or TuRBO optimizers, multi-testbench/multi-corner aggregation, and fixed-point reruns. Treat it as an optional backend pattern: install it in the same Cadence-capable environment, run its --doctor check first, then let the agent inspect the generated reports/manifests before claiming success.

Objective design

Return a scalar float. Return 1e6 on failure — never nan or inf, because these break the GP surrogate model and cause the optimizer to diverge.

Related skills

• spectre — Spectre simulation runner, netlist syntax, result parsing
• virtuoso — Maestro setup, schematic editing, design variable management