Grid Configuration

Beyond simple lists, Malet’s YAML config supports list comprehensions, grid sequences, and field grouping for complex experiment designs.

List comprehension

Generate grid values using Python-like expressions inside the YAML config:

lr: [10**{-i};1:1:5]

The general syntax is [{expression};{start}:{step}:{end}], which is equivalent to [expression for i in range(start, end, step)]. The expression can use the variable i and standard arithmetic operators.

More examples:

lr: [10**{-i};1:1:5]          # [0.1, 0.01, 0.001, 0.0001]
width: [2**{i};5:1:10]        # [32, 64, 128, 256, 512]
dropout: [{i*0.1};1:1:6]      # [0.1, 0.2, 0.3, 0.4, 0.5]

Grid sequences

Run a sequence of different grids by passing a list of dictionaries under grid:

grid:
    - optimizer: sgd
      lr: [0.001, 0.01]
      seed: [1, 2, 3]

    - optimizer: adam
      lr: [0.005]
      seed: [1, 2, 3]

This runs 2 x 3 = 6 configs for SGD, then 1 x 3 = 3 configs for Adam (9 total), instead of the full Cartesian product. This is useful when certain hyperparameter combinations are irrelevant and you don’t want to waste compute.

Grouping

Grouping ties multiple fields together so they vary in lockstep rather than forming a Cartesian product:

grid:
    group:
        optimizer: [[sgd], [adam]]
        lr: [[0.001, 0.01], [0.005]]
    seed: [1, 2, 3]

Here optimizer and lr are paired — (sgd, [0.001, 0.01]) and (adam, [0.005]) — then crossed with seed. This is equivalent to the grid sequence above but more compact.

The general pattern:

grid:
    group:
        cfg1: [A1, B1]
        cfg2: [A2, B2]
    cfg3: [1, 2, 3]

produces the same runs as:

grid:
    - cfg1: A1
      cfg2: A2
      cfg3: [1, 2, 3]

    - cfg1: B1
      cfg2: B2
      cfg3: [1, 2, 3]

The grouped fields cfg1 and cfg2 have paired values (A1, A2) and (B1, B2) — they are not crossed against each other.

Multiple groups

You can create multiple independent groups using a list under group:

grid:
    group:
        - cfg1: [A1, B1]
          cfg2: [A2, B2]
        - cfg3: [C1, D1]
          cfg4: [C2, D2]
    cfg5: [1, 2, 3]

Each group (cfg1, cfg2) and (cfg3, cfg4) is internally paired, but the two groups are crossed against each other and against cfg5.