Glossary

hawk’s own terms. For words shared across the family (manifest, sample, DLPack, certification row, …) see the family glossary.

plane

The role one argument plays for every sample: a per-sample input (Scalar), a shared constant (Param) or an output (Mutable[...]).

kernel kind

A declared shared shape for a family of kernels (KernelKind), grown by ordinary Python inheritance.

primitive

A function you register with hawk.ext.primitive together with its forward and, optionally, jvp/vjp rules, so it can appear in a kernel.

guard

Which masks gate a sample (hawk.ext.Guard): a sample runs only when none of the named masks, such as terminated or rejected, is set.

dispatch policy

How a per-sample branch between several formulas is compiled. It never changes what is computed.

tape

The record of the state a stepping kernel read at each step, kept so a gradient can be taken backward through a whole rollout.

jvp

Forward-mode derivative: how an output moves for a given change of the inputs.

vjp

Reverse-mode derivative: how a change of the output maps back to the inputs.

step vjp

The vjp of one step of a kernel that updates its planes in place (hawk.diff.step_vjp). It reads each plane’s value before the step, takes bar_<plane>_next (the gradient with respect to the value after the step) and returns bar_<plane> (the gradient with respect to the value before it).

derived

A kernel that hawk builds from another one, such as its jvp, vjp or taping twin.

compile cache

The store of compiled kernels. Building the same kernel again copies it from the cache instead of recompiling.

device image

The compiled GPU code (DeviceImage, PTX or SASS) hawk produces for a kernel; eagle launches it.

integer plane

A per-sample plane of 32-bit integers, declared Int32 (np.int32) or UInt32 (np.uint32); Param[Int32] declares an integer parameter. + - * wrap modulo 2^32, // and % follow Python’s sign rules (a zero divisor gives 0), & | ^ ~ << >> act on the bits (a shift count outside [0, 32) gives 0, or -1 for a negative value shifted right), as NumPy does. An integer never mixes with a float without a cast: hawk.math.real(n) gives the float, hawk.math.int32(x) / hawk.math.uint32(x) the integer (truncating toward zero, saturating at the type’s range, NaN to 0). An integer plane is never differentiated. Index is the separate 64-bit index type for addresses and selectors.

payload

The sealed bundle of aether’s C++ headers that hawk’s runtime GPU compiles build against. It ships in the aether-dsc package, so a GPU build needs no aether checkout.