Hitachi

Hitachi has developed the CMOS annealing machine, a non-Neumann architecture computer utilizing the structure of SRAM, a storage device, to perform optimization processing with the Ising model.

Solvers

Model	Solvers
Quadratic Unconstrained Binary Optimization (QUBO)	hitachi.cmos_annealer

You can specify the type of machine type to run the process from the following options (see the Hitachi API Reference for more details) and HitachiParameterModel for details on how to set the type:

• 3 : GPU 32bit(int)
• 4 : GPU 32bit(float)
• 5 : ASIC 4bit

QUBO

import strangeworks as sw

from strangeworks_optimization import StrangeworksOptimizer
from strangeworks_optimization_models.parameter_models import HitachiParameterModel
from dimod import BinaryQuadraticModel

sw.authenticate(api_key)

linear = {1: -2, 2: -2, 3: -3, 4: -3, 5: -2}
quadratic = {(1, 2): 2, (1, 3): 2, (2, 4): 2, (3, 4): 2, (3, 5): 2, (4, 5): 2}
model = BinaryQuadraticModel(linear, quadratic, "BINARY")

options = HitachiParameterModel(solver_type=5)

solver = 'hitachi.cmos_annealer'

so = StrangeworksOptimizer(
    model=model,
    options=options,
    solver=solver
)

sw_job = so.run()
print(f"Job slug: {sw_job.slug}")
print(f"Job status: {so.status(sw_job.slug)}")
results = so.results(sw_job.slug)
print(results.solution)

Ising Model

The model parameter is an array of integer values [x0, y0, x1, y1, p] with 5 elements representing the vertices or interactions of the Ising model. The order in which they are specified does not affect the calculation results.

x and y represent the coordinates (x-axis, y-axis) on the Ising model, respectively, and p represents the coefficient. Set the Ising model in the form x0 == x1, y0 == y1 to represent the vertex = first order term (magnetic field), and set x0, y0 and x1, y1 to be adjacent to each other to represent the interaction of two vertices.

Adjacent means up-down, left-right, and diagonal. An error occurs if the coordinate specification of two non-adjacent vertices is included.

import strangeworks as sw

from strangeworks_optimization import StrangeworksOptimizer
from strangeworks_optimization_models.problem_models import HitachiModelList
from strangeworks_optimization_models.parameter_models import HitachiParameterModel

sw.authenticate(api_key)

model = HitachiModelList(
    [
        [0, 0, 0, 1, 117],
        [0, 0, 1, 0, 104],
        [0, 0, 1, 1, 65],
        [0, 1, 1, 0, 72],
        [0, 1, 1, 1, 45],
        [1, 0, 1, 1, 40],
    ]
)

options = HitachiParameterModel(solver_type=5)

solver = 'hitachi.cmos_annealer'

so = StrangeworksOptimizer(
    model=model,
    options=options,
    solver=solver
)

sw_job = so.run()
print(f"Job slug: {sw_job.slug}")
print(f"Job status: {so.status(sw_job.slug)}")
results = so.results(sw_job.slug)
print(results.solution)

Parameters

from strangeworks_optimization_models.parameter_models import HitachiParameterModel

options = HitachiParameterModel(
        .....
    )

Key	Description	Data Type	Default Value	Minimum Value	Maximum Value
type	Execution machine type	integer	3	-	-
num_executions	Annealing execution count	integer	1	1	10
parameters	Execution parameter control setting	object	-	-	-
temperature_num_steps	Temperature change step number	integer	10	1	100
temperature_step_length	Length per temperature step	integer	100	1	1000
temperature_initial	Initial temperature	number	10.0	0 or more	3.402823e+38
temperature_target	Final temperature	number	0.01	0 or more	3.402823e+38
outputs	Control of values included in response	object	-	-	-
energies	Output energy value	boolean	true	-	-
spins	Output spin value array	boolean	true	-	-
execution_time	Output execution time (nsec)	boolean	false	-	-
num_outputs	Number of outputs of spin value and energy value	integer	0	0	num_executions
averaged_spins	Output average value per site of spin	boolean	false	-	-
averaged_energy	Output the average value of energy	boolean	false	-	-

Solvers

• hitachi.cmos_annealer

Embedding

To use embedding with Hitachi solvers, pass the embedding_parameters parameter to the solver.

from strangeworks_optimization_models.parameter_models import HitachiParameterModel

options = HitachiParameterModel(embedding_parameters={
    "chain_strength": 10,
    "anneal_schedule": [[0, 0], [1, 1]],
    "anneal_offsets": [0, 0],
    "annealing_time": 1,
    "auto_scale": True,
})

Parameter	Type	Default	Description
max_no_improvement	int	None	Maximum number of failed iterations to improve the current solution. Each iteration attempts to find an embedding for each variable such that it is adjacent to all its neighbours.
random_seed	int	None	Seed for the random number generator. If set to None, the seed is initialized using os.random().
timeout	int	None	Maximum time (in seconds) before the algorithm gives up.
max_beta	float	None	Qubits are assigned weight based on a formula (beta^n) where n is the number of chains containing that qubit. This value should be greater than 1. If None, max_beta is effectively infinite.
tries	int	None	Number of restart attempts before the algorithm stops. A typical restart takes between 1 and 60 seconds.
inner_rounds	int	None	Maximum number of iterations between restart attempts. If None, inner_rounds is effectively infinite.
chainlength_patience	int	None	Maximum number of failed iterations to improve chain lengths in the current solution.
max_fill	int	None	Restricts the number of chains that can simultaneously incorporate the same qubit during the search. Values above 63 are treated as 63. If None, max_fill is effectively infinite.
threads	int	None	Maximum number of threads to use. Parallelization is only advantageous where the expected degree of variables is significantly greater than the number of threads.
return_overlap	bool	None	Determines the function’s return value. If True, a 2-tuple is returned with the embedding and a boolean representing the embedding validity. If False, only an embedding is returned.
skip_initialization	bool	None	Skips the initialization pass if the chains passed through initial_chains and fixed_chains are semi-valid.
verbose	int	None	Level of output verbosity. Ranges from 0 (quiet) to 4 (detailed debugging).
interactive	bool	None	If True, the verbose output will be printed to stdout/stderr and keyboard interrupts will stop the embedding process, returning the current state to the user.
initial_chains	dict	None	Initial chains to be inserted into an embedding before fixed_chains are placed.
fixed_chains	dict	None	Fixed chains that are inserted into an embedding before the initialization pass and do not change during the algorithm.
restrict_chains	dict	None	Ensures that each chain is a subset of restrict_chains throughout the algorithm.
suspend_chains	dict	None	A metafeature implemented in the Python interface. Each entry is an iterable of iterables representing the target node labels.

Solvers

• DwaveSamplerParameterModel(embedding_parameters)
• HitachiParameterModel(embedding_parameters)