ulid() slow vs monotonic #126

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1. cmcnicholas commented on Sep 12, 2025

   

   cmcnicholas

   on Sep 12, 2025

   More actions

   Does it make sense that ulid() is so slow relative to monothonic? I ran this simple benchmark multiple times to test this library vs uuidv7, and it always returns around the same results:

   import { ulid, monotonicFactory } from 'ulid';
   
   function bench(name, fn, N = 5_000_000) {
     // warmup
     for (let i = 0; i < 200_000; i++) fn();
     const t0 = performance.now();
     for (let i = 0; i < N; i++) fn();
     const t1 = performance.now();
     console.log(`${name}: ${(N / ((t1 - t0) / 1000)).toFixed(1)} ids/sec`);
   }
   
   bench('uuidv7', uuidv7);
   bench('ulid', ulid);
   bench('ulid(monotonic)', monotonicFactory());
   

   The results

   uuidv7: 5486105.0 ids/sec
   ulid: 31140.8 ids/sec
   ulid(monotonic): 2054127.8 ids/sec
   

   why is ulid() much slower than monotonic? and why is monotonic slower than uuidv7?

   Looks like some work is done on every call to ulid in detectPRNG() and seed creation (tiny but it is repeated).

   A way to improve that without needing the factory is if they allowed us to call detectPRNG() so we could store it once. e.g.

   import { ulid, detectPRNG } from 'ulid';
   
   const prng = detectPRNG();
   
   export function id() {
     return ulid(Date.now(), prng);
   }

   this avoids the repeated testing of detectPRNG.

   I think there might be room for improvement though, I can see allocating the Uint32Array each time a call is made is also pretty expensive: https://github.com/ulid/javascript/blob/master/source/ulid.ts#L51

   Suggestion would be they move the array initialisation to the outer part of the function and reuse it.

           const buffer = new Uint8Array(1);
           return () => {
               globalCrypto.getRandomValues(buffer);
               return buffer[0] / 0xff;
           };

   If you know your environment its running in you can just add this today e.g.

   import { ulid } from 'ulid';
   
   const buffer = new Uint8Array(1);
   function prng() {
     crypton.getRandomValues(buffer);
     return buffer[0] / 0xff;
   }
   
   export function id() {
     return ulid(undefined, prng);
   }

   Anyway, just some thoughts.
2. cmcnicholas commented on Sep 13, 2025

   

   cmcnicholas

   on Sep 13, 2025

   More actions

   Does it make sense that ulid() is so slow relative to monothonic? I ran this simple benchmark multiple times to test this library vs uuidv7, and it always returns around the same results:

   import { ulid, monotonicFactory } from 'ulid';
   
   function bench(name, fn, N = 5_000_000) {
     // warmup
     for (let i = 0; i < 200_000; i++) fn();
     const t0 = performance.now();
     for (let i = 0; i < N; i++) fn();
     const t1 = performance.now();
     console.log(`${name}: ${(N / ((t1 - t0) / 1000)).toFixed(1)} ids/sec`);
   }
   
   bench('uuidv7', uuidv7);
   bench('ulid', ulid);
   bench('ulid(monotonic)', monotonicFactory());
   

   The results

   uuidv7: 5486105.0 ids/sec
   ulid: 31140.8 ids/sec
   ulid(monotonic): 2054127.8 ids/sec
   

   why is ulid() much slower than monotonic? and why is monotonic slower than uuidv7?

   just opened a PR after I went on a bit of a dive through the code #127 makes ulid work about 45% faster.