bam-solver

Python wrapper for the BAM (Branch-And-Model) derivative-free global optimization solver.

Three layers of API ergonomics:

1. bam.minimize: SciPy-style functional facade.
2. Bam: full-control mirror of the BAM C API.
3. bam.AskTell: ask/tell interface for off-process or asynchronous evaluators.

Requirements

• Python >= 3.10
• Linux (x86_64, aarch64), macOS (Intel, Apple Silicon), or Windows (x86_64)

No compiler and no separate BAM installation are needed: each wheel bundles libbam and its runtime libraries inside the package. The only runtime dependencies are NumPy and CFFI, installed automatically.

Installation

pip install bam-solver

That is all; there is nothing else to install or configure to start solving. BAM runs in free mode for small problems; larger problems need a license (see Licensing below).

Building from source (maintainers/contributors only) requires a local BAM build providing bam.h and libbam.*:

BAM_INCLUDE_DIR=/path/to/bam/include BAM_LIB_DIR=/path/to/bam/lib \
    uv build --wheel

See release/README.md for the full in-house build/test/publish process.

Quick examples

Functional (SciPy-style): bam.minimize

import bam

def shc(x):
    x1, x2 = x
    return ((4 - 2.1*x1**2 + x1**4/3) * x1**2
            + x1*x2 + (-4 + 4*x2**2) * x2**2)

res = bam.minimize(shc, x0=[0, 0],
                   bounds=[(-3, 3), (-1.5, 1.5)],
                   options={"max_evals": 80})
print(res.x, res.fun, res.nfev, res.message)

bam.minimize is also usable as the method= argument to scipy.optimize.minimize:

from scipy.optimize import minimize
res = minimize(shc, [0, 0], method=bam.minimize,
               bounds=[(-3, 3), (-1.5, 1.5)],
               options={"max_evals": 80})

Bounds are optional: omit them and BAM uses its default box, exactly as the full-control Bam class and the C API do. Common BAM options keys: max_evals, max_time, max_iter, max_no_gain, print_to_screen, outfname, tracefname, evalsfname, prevals; setting outfname/tracefname enables the listing/trace file, and evalsfname is required whenever prevals is nonzero. Any other BAM option is forwarded verbatim with a single warning naming it, or pass it through raw_options={"name": value} to forward without the warning. The wrapper also accepts x_evaluated/f_evaluated (pre-evaluated points) and history=True (attaches the full x_hist/f_hist evaluation trajectory to the result). Use integrality=[0, 1, ...] for mixed-integer problems (SciPy convention).

Ask/tell: bam.AskTell

For evaluators that BAM cannot call directly (a remote simulator, a long-running batch job, an HPC scheduler):

import bam

opt = bam.AskTell(nvars=2, bounds=[(-3, 3), (-1.5, 1.5)], max_evals=80)
while not opt.is_done():
    try:
        x = opt.ask()
    except StopIteration:
        break
    f = my_simulator(x)             # may take seconds, minutes, hours
    opt.tell(x, f)
res = opt.recommendation()
print(res.x, res.fun)

BAM runs in a background thread; ask() blocks until BAM requests a point, tell(x, f) feeds the result back. Bounds are optional here too (nvars gives the dimension). Use the context-manager form (with bam.AskTell(...) as opt: ...) so the worker thread is always cleaned up. One ask outstanding at a time; pickling / cross-process resume is not supported.

Full-control: Bam

import numpy as np
from bam import Bam

with Bam(nvars=2) as solver:
    solver.set_real_vector("xmin", [-3, -1.5])
    solver.set_real_vector("xmax", [ 3,  1.5])
    solver.set_int("maxevals", 80)
    solver.set_objective(shc)
    result = solver.solve(x0=[0.0, 0.0])

print(result.x, result.fun, result.nfev, result.message)

Licensing

BAM is free for problems with up to two variables. Larger problems require a license file, free for academic users at https://minlp.com/bam-licenses.

The wrapper defers to BAM for license-file discovery; BAM searches CWD, the executable's directory, and every entry of $PATH for a file whose name is configured via the licfname string option (default bamlice.txt). To override:

import bam
bam.set_license_file("/path/to/bam.lic")
# or set BAM_LICENSE_FILE in the environment before importing bam

Diagnostics: bam.license_status() returns a dict with state, path, and free_limit_nvars. If BAM is in free mode at solve time the wrapper emits a one-time BamLicenseWarning.

Tests

pytest                                   # runs the in-package suite
BAM_TEST_LICENSE=/usr/local/bin/bamlice.txt pytest    # also exercises licensed-mode paths