skainet-data-dsl

Building blocks for tensor data: creation, initialisation, slicing, and transform pipelines for preprocessing. This skill is a cheatsheet — DSL skills teach usage rather than enforce constraints.

When to use

• Constructing a tensor literal with a known shape and fill (zeros, ones, fill, random, fromArray).
• Slicing or viewing an existing tensor.
• Building a preprocessing pipeline (rescale → normalize → unsqueeze → reshape).
• Choosing a dtype tag (FP32, FP16, Int8, Int32, Int4, Ternary).

When NOT to use

• Asserting on tensor values in tests — skainet-testing.
• Defining neural network architecture with sequential { } / dag { } — skainet-nn-dsl.
• Exposing a tensor builder to Java — skainet-java-interop.
• Editing where a tensor file lives in source sets — kmp.

Cheatsheet

Two equivalent tensor entry points

// (a) Direct entry — tensor(executionContext, dtypeKClass) { ... }
val t = tensor<FP32, Float>(ctx, FP32::class) {
    tensor {
        shape(2, 3) {
            from(0f, 1f, 2f, 10f, 11f, 12f)
        }
    }
}
// from: SKaiNET/skainet-lang/skainet-lang-core/src/commonMain/kotlin/sk/ainet/lang/tensor/dsl/TensorDSL.kt:17-25

// (b) Phase-aware entry — data<T, V>(ctx) { tensor { ... } }
val t = data<FP32, Float>(ctx) {
    tensor {
        shape(2, 3) {
            from(0f, 1f, 2f, 10f, 11f, 12f)
        }
    }
}
// from: SKaiNET/skainet-lang/skainet-lang-core/src/commonTest/kotlin/sk/ainet/readme/ReadmeSnippetsTest.kt:18-32

Use form (b) when you're already inside a phase-aware execution context (training vs eval) and want phase-tagged tensors. Use form (a) for plain inference / tests / examples.

Initialisation strategies inside shape(...) { ... }

shape(28, 28) { zeros() }           // FloatArray of zeros
shape(28, 28) { ones() }
shape(28, 28) { full(0.5f) }        // every element = 0.5
shape(2, 3)   { from(1f, 2f, 3f, 4f, 5f, 6f) }  // explicit values, length must equal shape volume
shape(2, 3)   { fromArray(myFloatArray) }
shape(28, 28) { randn(mean = 0f, std = 0.02f) }
shape(28, 28) { uniform(min = -1f, max = 1f) }
shape(28, 28) { init { idx -> (idx[0] + idx[1]).toFloat() } }
shape(28, 28) { randomInit({ rng -> rng.nextFloat() }) }
// from: SKaiNET/skainet-lang/skainet-lang-core/src/commonMain/kotlin/sk/ainet/lang/tensor/dsl/TensorDSL.kt:50-108

Slice views — sliceView { segment { ... } }

val view = bigTensor.sliceView {
    segment { range(0, 10) }      // dim 0: indices 0..9 (exclusive end)
    segment { at(5) }             // dim 1: pick exactly index 5
    segment { all() }             // dim 2: keep everything
    segment { step(0, 20, 2) }    // dim 3: every 2nd index from 0 to 20
}
// from: SKaiNET/skainet-lang/skainet-lang-core/src/commonMain/kotlin/sk/ainet/lang/tensor/TensorSliceBuilder.kt:18-26

The number of segment { } blocks MUST equal the rank of the tensor — validate(tensorShape) throws otherwise.

Transform pipelines

val preprocess = pipeline<Tensor<FP32, Float>>()
    .rescale(ctx, scale = 255f)
    .normalize(ctx, mean = imagenetMean, std = imagenetStd, channelAxis = -1)
    .unsqueeze(0)                 // add batch dim at position 0

val batch = preprocess(rawImageTensor)
// from: SKaiNET/skainet-data/skainet-data-transform/src/commonMain/kotlin/sk/ainet/data/transform/TensorTransformDsl.kt:18-50

Available transform extensions: rescale, normalize, scaleAndShift, clamp, reshape (more to follow — file is the source of truth).

Dtype tags

tensor<FP32, Float>(...) — the value-type parameter follows the table above. tensor<FP32, Int>(...) will not type-check.

Workflow

1. Decide whether the tensor is part of a phase (training-aware) or a plain literal — pick tensor(...) { tensor { } } or data(...) { tensor { } } accordingly.
2. Pick the dtype + value-type pair from the table.
3. Pick the initialisation: deterministic literals (from, fromArray, full) for tests; randn / uniform for parameter init; init / randomInit for custom generators.
4. For preprocessing chains, compose transforms in pipeline<...>() — every step takes the ExecutionContext so the tensors land in the right backend.
5. Reach for sliceView { segment { ... } } only when the operation isn't already covered by a tensor-op like narrow, unsqueeze, squeeze, flatten (those are simpler and cheaper).

Related skills

• The ExecutionContext itself comes from DirectCpuExecutionContext.create() (CPU) or DefaultNeuralNetworkExecutionContext() for the phase-aware form — see ../skainet-inference/SKILL.md.
• Feeding the tensor into a network — see ../skainet-nn-dsl/SKILL.md.
• Adding the SKaiNET dependency that exposes tensor { } to your Gradle project — see ../skainet-consumer-setup/SKILL.md.
• Calling these from Java — see ../skainet-java-consumer/SKILL.md.
• (In-repo only) Comparing computed tensors against expected values in tests — see the contributor skainet-testing skill.

Anti-patterns

// WRONG — wrong value-type for the dtype
val t = tensor<FP32, Int>(ctx, FP32::class) { tensor { shape(2) { from(1, 2) } } }

// RIGHT — match the dtype/value-type table
val t = tensor<FP32, Float>(ctx, FP32::class) { tensor { shape(2) { from(1f, 2f) } } }
val ti = tensor<Int32, Int>(ctx, Int32::class) { tensor { shape(2) { from(1, 2) } } }

// WRONG — manually slicing with index loops in user code
val rows = (0 until 10).map { i -> bigTensor[i] }

// RIGHT — sliceView
val rows = bigTensor.sliceView { segment { range(0, 10) }; segment { all() } }

// WRONG — chained scalar ops to do preprocessing
val x1 = raw.ops.divScalar(raw, 255f)
val x2 = x1.ops.subScalar(x1, mean)
val x3 = x2.ops.divScalar(x2, std)

// RIGHT — a transform pipeline
val pre = pipeline<Tensor<FP32, Float>>()
    .rescale(ctx, 255f)
    .normalize(ctx, floatArrayOf(mean), floatArrayOf(std))
val out = pre(raw)

References

• references/tensor-builders.md — every entry point on TensorCreationScope and ShapeBuilder, with signatures.
• references/transform-ops.md — every transform extension function in skainet-data-transform, with arguments and defaults.