Selection of GPU and data quantity in IndexIVFPQ experiment

[Aurevoir-68]

Summary

Platform

OS:

Faiss version:

Installed from:

Faiss compilation options:

Running on:

• CPU
• GPU

Interface:

• C++
• Python

Reproduction instructions

The experiment was carried out in NVIDIA docker，nb = 500w, d = 512, There are three graphics cards：

0. 1080(8G)
1. 2080ti(11G)
2. 1080(8G)

I encountered the following problems in the ivfpq experiment:

(1) When running a program with multiple GPUs, the difference between faiss::gpu::index_ cpu_ to_ gpu_multiple method and faiss::gpu::GpuiIndexIVFPQ?

(2) Can faiss::gpu::GpuiIndexIVFPQ method control the number of graphics cards and which one ?(I know the method of faiss:: GPU:: index_ cpu_to_gpu_ Multiple can control the number of GPUs)

(3) When I use nb = 4000000, d = 512,there is no problem. **When I modify nb = 5000000, an error is reported:

terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc
Aborted(core dumped)

In addition, the graphics card uses one 2080ti by default. Shouldn't it be 1080 in order?

faiss::IndexFlatL2 quantizer(d);
faiss::IndexIVFPQ cpu_index(&quantizer,d,nlist,m,8);
faiss::Index * gpu_index=faiss::gpu::index_cpu_to_gpu_multiple(res,devs,&cpu_index);

faiss::gpu::GpuIndexIVFPQConfig config;
config.device = 1;
faiss::gpu::GpuIndexIVFPQ index(&res,d,nlist,m,8,faiss::METRIC_L2,config);

[wickedfoo]

1. index_cpu_to_gpu_multiple is just a wrapper around calling the GpuIndexIVFPQ constructor. In C++ I'd probably prefer calling the constructor yourself, though the multiple part wraps the indices in an IndexShards or IndexReplicas object, which dedicates a separate thread to each GPU. In order to effectively use multiple GPUs you'll want a separate CPU thread for each index on each GPU.

2. The GpuIndexIVFPQConfig object contains a field device that says which GPU a particular index will use.

3. yes. Note that 5000000 x 512 x sizeof(float) is 10.24 GB, which is likely exceeding the memory available/remaining on your GPU.

4. 2080ti vs 1080, you are specifying config.device = 1. Nvidia specifies devices numbered from 0. You yourself have the 2080ti device as device Faiss not working #1 above, so don't see what the issue is here?

[mdouze]

no activity, closing.