Offline IVF powered by faiss big batch search (facebookresearch#3175)

Summary:
This PR introduces the offline IVF (OIVF) framework  which contains some tooling to run search using IVFPQ indexes (plus OPQ pretransforms) for large batches of queries using [big_batch_search](https://github.com/mlomeli1/faiss/blob/main/contrib/big_batch_search.py) and GPU faiss. See the [README](https://github.com/mlomeli1/faiss/blob/oivf/demos/offline_ivf/README.md) for details about using this framework.

This PR includes the following unit tests, which can be run with the unittest library as so:
````
~/faiss/demos/offline_ivf$ python3 -m unittest tests/test_iterate_input.py -k test_iterate_back
````

In test_offline_ivf:
````
test_consistency_check
test_train_index
test_index_shard_equal_file_sizes
test_index_shard_unequal_file_sizes
 test_search
test_evaluate_without_margin
test_evaluate_without_margin_OPQ
test_evaluate_with_margin
test_split_batch_size_bigger_than_file_sizes
test_split_batch_size_smaller_than_file_sizes
test_split_files_with_corrupted_input_file
````

In test_iterate_input:
````
test_iterate_input_file_larger_than_batch
test_get_vs_iterate
test_iterate_back
````

Pull Request resolved: facebookresearch#3175

Reviewed By: algoriddle

Differential Revision: D52218447

Pulled By: mlomeli1

fbshipit-source-id: 78b12457c79b02eb2c9ae993560f2e295798e7e5

demos/offline_ivf/README.md

@@ -0,0 +1,52 @@
+
+# Offline IVF
+
+This folder contains the code for the offline ivf algorithm powered by faiss big batch search.
+
+Create a conda env:
+
+`conda create --name oivf python=3.10`
+
+`conda activate oivf`
+
+`conda install -c pytorch/label/nightly -c nvidia faiss-gpu=1.7.4`
+
+`conda install tqdm`
+
+`conda install pyyaml`
+
+`conda install -c conda-forge submitit`
+
+
+## Run book
+
+1. Optionally shard your dataset (see create_sharded_dataset.py) and create the corresponding yaml file `config_ssnpp.yaml`. You can use `generate_config.py` by specifying the root directory of your dataset and the files with the data shards
+
+`python generate_config`
+
+2. Run the train index command
+
+`python run.py --command train_index --config config_ssnpp.yaml --xb ssnpp_1B`
+
+
+3. Run the index-shard command so it produces sharded indexes, required for the search step
+
+`python run.py --command index_shard --config config_ssnpp.yaml --xb ssnpp_1B`
+
+
+6. Send jobs to the cluster to run search
+
+`python run.py  --command search --config config_ssnpp.yaml --xb ssnpp_1B  --cluster_run --partition <PARTITION-NAME>`
+
+
+Remarks about the `search` command: it is assumed that the database vectors are the query vectors when performing the search step.
+a. If the query vectors are different than the database vectors, it should be passed in the xq argument
+b. A new dataset needs to be prepared (step 1) before passing it to the query vectors argument `–xq`
+
+`python run.py --command search --config config_ssnpp.yaml --xb ssnpp_1B --xq <QUERIES_DATASET_NAME>`
+
+
+6. We can always run the consistency-check for sanity checks!
+
+`python run.py  --command consistency_check--config config_ssnpp.yaml --xb ssnpp_1B`
+

demos/offline_ivf/config_ssnpp.yaml

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+d: 256
+output: /checkpoint/marialomeli/offline_faiss/ssnpp
+index:
+  prod:
+  - 'IVF8192,PQ128'
+  non-prod:
+  - 'IVF16384,PQ128'
+  - 'IVF32768,PQ128'
+nprobe:
+  prod:
+    - 512
+  non-prod:
+    - 256
+    - 128
+    - 1024
+    - 2048
+    - 4096
+    - 8192
+
+k: 50
+index_shard_size: 50000000
+query_batch_size: 50000000
+evaluation_sample: 10000
+training_sample: 1572864
+datasets:
+  ssnpp_1B:
+    root: /checkpoint/marialomeli/ssnpp_data
+    size: 1000000000
+    files:
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000000.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000001.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000002.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000003.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000004.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000005.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000006.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000007.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000008.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000009.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000010.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000011.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000012.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000013.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000014.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000015.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000016.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000017.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000018.npy
+      size: 50000000
+    - dtype: uint8
+      format: npy
+      name: ssnpp_0000000019.npy
+      size: 50000000

demos/offline_ivf/create_sharded_ssnpp_files.py

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+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+import numpy as np
+import argparse
+import os
+
+
+def xbin_mmap(fname, dtype, maxn=-1):
+    """
+    Code from
+    https://github.com/harsha-simhadri/big-ann-benchmarks/blob/main/benchmark/dataset_io.py#L94
+    mmap the competition file format for a given type of items
+    """
+    n, d = map(int, np.fromfile(fname, dtype="uint32", count=2))
+    assert os.stat(fname).st_size == 8 + n * d * np.dtype(dtype).itemsize
+    if maxn > 0:
+        n = min(n, maxn)
+    return np.memmap(fname, dtype=dtype, mode="r", offset=8, shape=(n, d))
+
+
+def main(args: argparse.Namespace):
+    ssnpp_data = xbin_mmap(fname=args.filepath, dtype="uint8")
+    num_batches = ssnpp_data.shape[0] // args.data_batch
+    assert (
+        ssnpp_data.shape[0] % args.data_batch == 0
+    ), "num of embeddings per file should divide total num of embeddings"
+    for i in range(num_batches):
+        xb_batch = ssnpp_data[
+            i * args.data_batch : (i + 1) * args.data_batch, :
+        ]
+        filename = args.output_dir + f"/ssnpp_{(i):010}.npy"
+        np.save(filename, xb_batch)
+        print(f"File {filename} is saved!")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--data_batch",
+        dest="data_batch",
+        type=int,
+        default=50000000,
+        help="Number of embeddings per file, should be a divisor of 1B",
+    )
+    parser.add_argument(
+        "--filepath",
+        dest="filepath",
+        type=str,
+        default="/datasets01/big-ann-challenge-data/FB_ssnpp/FB_ssnpp_database.u8bin",
+        help="path of 1B ssnpp database vectors' original file",
+    )
+    parser.add_argument(
+        "--filepath",
+        dest="output_dir",
+        type=str,
+        default="/checkpoint/marialomeli/ssnpp_data",
+        help="path to put sharded files",
+    )
+
+    args = parser.parse_args()
+    main(args)