168 lines
7.6 KiB
Markdown
168 lines
7.6 KiB
Markdown
# Quimb MPI Benchmark Suite
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Demonstrates MPI-enabled tensor network simulation using quimb with 2 MPI processes.
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## Files
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- **quimb_mpi.sh** — Main benchmark sweep script using `mpirun -np 2`
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- **expectation_mps_mpi.json** — Expectation mode with MPS (default for expectation)
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- **expectation_dense_mpi.json** — Expectation mode, dense tensor network
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- **dense_vector_mps_mpi.json** — State extraction with MPS (default for state)
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- **dense_vector_dense_mpi.json** — State extraction, dense tensor network
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## Key Differences from `/scripts/quimb/`
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- Each `python compare.py` call wrapped with `mpirun -np 2` to enable MPI parallelization
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- All JSON configs include `"MPI_enabled": true`
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- Default file names include `_mpi` suffix to distinguish from single-process configs
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- Filenames in logs clearly show MPI mode (e.g., `expectation_mps_mpi.json`)
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## Configuration Files
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### Expectation Modes (computing Hamiltonian expectation values)
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- **expectation_mps_mpi.json**: MPI-enabled, uses Matrix Product State (MPS) tensor network ansatz; good for larger systems with limited bond dimension
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- **expectation_dense_mpi.json**: MPI-enabled, uses dense tensor network; full contraction without MPS truncation
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### State Modes (full state vector computation)
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- **dense_vector_mps_mpi.json**: MPI-enabled, extracts full state using MPS contraction (faster, bounded memory)
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- **dense_vector_dense_mpi.json**: MPI-enabled, extracts full state using dense tensor (maximum memory usage)
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## Usage
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```bash
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cd /ssd_data/tankya2/code/ASC_2026_prism/ASC-2026/qibojit-benchmarks/scripts/quimb_mpi
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# Run with defaults (all matching dense_vector*.json and expectation*.json configs)
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./quimb_mpi.sh
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# Test only expectation mode, custom qubit sizes
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modes="expectation" nqubits_list="8 10 12" ./quimb_mpi.sh
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# Test dense vector only with one explicit config
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state_cfg=dense_vector_dense_mpi.json modes="dense_vector" ./quimb_mpi.sh
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# Restrict the sweep to a chosen subset of configs
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EXPECTATION_CONFIGS="expectation_mps_mpi.json expectation_dense_mpi.json" ./quimb_mpi.sh
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# Use 4 MPI processes (if testing scalability)
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np=4 ./quimb_mpi.sh
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```
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## Supported Circuits
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### ✓ Fully Supported (Numerically Validated)
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| Circuit | Alias | Parameters | Status | Notes |
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|---------|-------|------------|--------|-------|
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| **qft** | — | none | ✓ Works | Quantum Fourier Transform; aligned with qibojit |
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| **variational** | — | nlayers | ✓ Works | Parameterized circuit; aligned with qibojit |
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| **bv** | bernstein-vazirani | none | ✓ Works | Bernstein-Vazirani algorithm; aligned with qibojit |
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| **hs** | hidden-shift | none | ✓ Works | Hidden-shift problem; aligned with qibojit |
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| **qaoa** | — | nlayers | ✓ Works | QAOA with RZZ gate support; aligned with qibojit |
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### ❌ Not Supported
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| Circuit | Issue | Notes |
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|---------|-------|-------|
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| **qv** | Qiskit API compatibility | quantum-volume uses deprecated qiskit `.qasm()` method (v3.0+); not specific to quimb |
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## Environment Variables
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| Variable | Default | Description |
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|----------|---------|-------------|
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| `nqubits_list` | `6 8 10` | Space-separated qubit counts to benchmark |
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| `circuits` | `qaoa` | Space-separated circuit names |
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| `modes` | `dense_vector expectation` | Benchmark modes (dense_vector, expectation) |
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| `nlayers` | `2` | Layers for layered circuits (variational, qaoa) |
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| `np` | `2` | Number of MPI processes (mpirun -np) |
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| `nreps` | `1` | Repetitions per benchmark |
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| `filename` | `quimb_benchmark_mpi.dat` | Output log file |
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| `precision` | `complex128` | NumPy dtype (complex128 or complex64) |
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| `exp_cfg` | unset | Optional single expectation config; when unset, all `expectation*.json` files are swept |
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| `state_cfg` | unset | Optional single dense-vector config; when unset, all `dense_vector*.json` files are swept |
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| `EXPECTATION_CONFIGS` | unset | Optional space-separated subset of expectation configs to run |
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| `STATE_CONFIGS` | unset | Optional space-separated subset of dense-vector configs to run |
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## Results
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Results are stored in `/qibojit-benchmarks/benchmarks/results/` with filename prefix `quimb_benchmark_mpi.dat` by default (configurable via `filename=` env var).
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Each benchmark includes:
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- **import_time** — Backend initialization time
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- **creation_time** — Circuit creation time
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- **dry_run_time** — First execution time (warm-up)
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- **simulation_times** — Execution times for nreps runs
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- **expectation_result** — Observable expectation values (for expectation mode)
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## Observable
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By default, expectation uses:
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- **X on qubit 0**, identity on remaining qubits
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- Configurable via `pauli_pattern` in JSON config (e.g., `"XIIII"` for 5 qubits)
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## Reference Validation
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Each benchmark run automatically includes a **qibojit (numba) reference** with the same observable configuration, enabling direct numerical comparison for validation.
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Example:
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```
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[expectation MPI] quimb + variational @ 6q: 0.2019...
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[qibojit ref] numba + variational @ 6q: 0.2019... ✓ aligned
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```
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## Supported Circuits
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### ✓ Fully Supported (Numerically Validated)
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| Circuit | Alias | Parameters | Status | Notes |
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|---------|-------|------------|--------|-------|
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| **qft** | — | none | ✓ Works | Quantum Fourier Transform; aligned with qibojit |
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| **variational** | — | nlayers | ✓ Works | Parameterized circuit; aligned with qibojit |
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| **bv** | bernstein-vazirani | none | ✓ Works | Bernstein-Vazirani algorithm; aligned with qibojit |
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| **hs** | hidden-shift | none | ✓ Works | Hidden-shift problem; aligned with qibojit |
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| **qaoa** | — | nlayers | ✓ Works | QAOA with RZZ gate support; aligned with qibojit |
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### ❌ Not Supported
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| Circuit | Issue | Notes |
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|---------|-------|-------|
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| **qv** | Qiskit API compatibility | quantum-volume uses deprecated qiskit `.qasm()` method (v3.0+); not specific to quimb |
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## Notes
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- **Intel MPI Fabric:** On Prism, automatically sets `I_MPI_FABRICS=shm` (shared-memory fabric) for single-node local runs
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- **Observable:** X on first qubit, identity on rest (configurable via `pauli_pattern` in JSON)
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- **Reference:** qibojit (numba backend) included automatically with aligned observable for validation
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- **RZZ Gate:** Full support for QAOA and algorithms using two-qubit Ising rotations
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- **cu1 Gate:** Fully supported in expectation value mode (QFT compatible)
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- **Numerical Alignment:** All benchmarks automatically include qibojit reference with identical observable for validation
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## MPI Enable/Disable
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To test without MPI, use configs from `/scripts/quimb/` instead:
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```bash
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# Compare: MPI vs no MPI
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./quimb_mpi.sh # with MPI (2 processes)
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cd ../quimb && ./quimb_local.sh # without MPI (single process)
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```
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## Tensor Network Options
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Quimb supports both MPS (Matrix Product State) and dense tensor network contractions. By default the script sweeps every matching JSON file in this folder, or you can target individual configs:
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```bash
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# Compare MPS vs dense at same nqubits with MPI
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exp_cfg=expectation_mps_mpi.json nqubits_list="12" ./quimb_mpi.sh
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exp_cfg=expectation_dense_mpi.json nqubits_list="12" ./quimb_mpi.sh
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```
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MPS is typically faster and uses bounded memory, while dense provides full accuracy without truncation.
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## Additional Notes
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- **Bond Dimension:** MPS modes use max_bond_dimension=20 by default; adjust in JSON for memory/accuracy tradeoff
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- **SVD Cutoff:** Set to 1e-10 for high accuracy; increase for faster execution with acceptable loss tolerance
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- **Scaling:** MPI parallelization enables larger systems; test with np=4, np=8, etc. for scaling studies
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- **Single-Node MPI:** Default `-np 2` demonstrates MPI capability on local machine; for cluster runs, adjust `-np` and node configuration
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