package optint

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Efficient integer types on 64-bit architectures

Install

Dune Dependency

Authors

Maintainers

Sources

optint-0.2.0.tbz
sha256=1dcbe0b6b6031f77db33028c87138fdb3bf90f92915e3b6629ddeb30a0d3000b
sha512=7d4b63c82b1dc1e363a892895c1a612bac3dcd33c27e2c27e8ea2e8868d659413226c7a0d7bdcac423f7fb016069d0de90c3eaa68986da6aea69e1f1ca583f18

Description

This library provides two new integer types, Optint.t and Int63.t, which guarantee efficient representation on 64-bit architectures and provide a best-effort boxed representation on 32-bit architectures.

Implementation depends on target architecture.

Published: 08 Apr 2022

README

Optint - Efficient integer types on 64-bit architectures

This library provides two new integer types, Optint.t and Int63.t, which guarantee efficient representation on 64-bit architectures and provide a best-effort boxed representation on 32-bit architectures.

Goal

The standard Int32.t and Int64.t types provided by the standard library have the same heap-allocated representation on all architectures. This consistent representation has costs in both memory and run-time performance.

On 64-bit architectures, it's often more efficient to use the native int directly. This library provides types to do exactly this:

  • Optint.t: an integer containing at least 32 bits. On 64-bit, this is an immediate integer; on 32-bit, it is a boxed 32-bit value. The overflow behaviour is platform-dependent.

  • Int63.t: an integer containing exactly 63 bits. On 64-bit, this is an immediate integer; on 32-bit, it is a boxed 64-bit integer that is wrapped to provide 63-bit two's complement semantics. The two implementations are observationally equivalent, modulo use of Marshal and Obj.

In summary:

Integer type 32-bit representation 64-bit representation Semantics
Stdlib.Int.t 31-bit immediate ✅ 63-bit immediate ✅ Always immediate
Stdlib.Nativeint.t 32-bit boxed ❌ 64-bit boxed ❌ Exactly word size
Stdlib.Int32.t 32-bit boxed ❌ 32-bit boxed ❌ Exactly 32 bits
Stdlib.Int64.t 64-bit boxed ❌ 64-bit boxed ❌ Exactly 64 bits
Optint.t (new) 32-bit boxed ❌ 63-bit immediate ✅ At least 32 bits
Int63.t (new) 64-bit boxed ❌ 63-bit immediate ✅ Exactly 63 bits

These new types are safe and well-tested, but their architecture-dependent implementation makes them unsuitable for use with the Marshal module. Use the provided encode and decode functions instead.

Dependencies (2)

  1. dune
  2. ocaml >= "4.07.0"

Dev Dependencies (3)

  1. fmt with-test
  2. monolith with-test
  3. crowbar with-test & >= "0.2"

Conflicts

None

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