Alternatives to Vmap

[pharringtonp19]

I recognize that vmap is helpful for writing code without having to explicitly think about "batching".

I am wondering though if is the preferred way to execute "generic" jax code in parallel on a single device?

For instance, let's say I want to execute multiple functions in parallel, what would be the preferred way I do this within Jax?

[selamw1]

Hi @pharringtonp19,

Considering recent advancements in JAX, while vmap excels at vectorizing batch operations, for complex scenarios involving parallel execution on single or multiple devices, JAX offers advanced strategies: jit for automatic parallelism and shard_map for explicit control over parallelism.

• jax.jit for Automatic Parallelism: jit enables Just-In-Time compilation, optimizing code execution by automatically partitioning computation and managing data sharding. Designed for both single and multi-device environments, jit simplifies parallel execution, enhancing performance without requiring manual intervention. This automatic compiler-based parallelization allows you to write code as if for a single device, while JAX’s compiler efficiently distributes the workload across available resources.

• shard_map for Explicit Control over Parallelism: shard_map introduces a single-program multiple-data (SPMD) model for explicit control over parallelism. This approach is ideal for scenarios requiring precise control over how data is distributed and computations are parallelized. Unlike jit, shard_map allows you to manually write partitioned code and define explicit collective communication operations, offering granular control. Notably, shard_map complements jit and can be used together, providing a flexible framework for both automatic and manual parallelization strategies depending on the complexity and requirements of your tasks.

Choosing between jit and shard_map depends on your control needs. For automatic optimization (simpler code), use jit. For fine-tuning parallelism (more control), use shard_map. See: when should you use shmap and when should you use pjit?

Note:

• Previously experimental, shard_map API is now stable and recommended for explicit parallelization (shmap is moving out of experimental [shard-map] move shmap out of experimental, add docstring #20124).

[pharringtonp19]

@selamw1 Thanks for the thorough explanation!