package optint

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Efficient integer types on 64-bit architectures

Install

Dune Dependency

Authors

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Sources

optint-0.3.0.tbz
sha256=295cff2c134b0385b13ba81d5005d9f841ba40d4a502aed10c997f239ef1147b
sha512=15ec97a076584e8ea28c589f1db3b9a0dd6fd5a7950528a1d136761cc13bca0e6e7bf6e0f87c73578a37393c213a7a0f3e7beaabd924e176459b29af52b8dd11

README.md.html

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.

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