is it in a file or in memory, does in come in chunks and in what formats is it.

Sorry, but I don't get your drift?

1. The values will be in memory before I can manipulate them.

   They will be persisted to disk between runs.

2. Does what come in chunks?

   They (the millions of 24-byte values) will be accessed via memory mapped IO.

3. The format is as described. 32x6-bit values encoded as a 24-byte bitstring.

   On disk each record will consist of the 24-byte value + 8 associated bytes.

It matters if you can optimise the I/O from disk. The drift is that performance should rarely be addressed too specifically.

One world, one people

It matters if you can optimise the I/O from disk.

Why? They are only read or written from disk once or a few times per run. Runs last many hours, or days. They are decoded many millions of times. The two are unrelated.

The values are compressed because there are many millions of them, and the 25% space saving is crucial both on disk and in memory. They are kept compressed whilst in memory because otherwise they would need to be paged to disk far more often.

The drift is that performance should rarely be addressed too specifically.

Hm. So you'd optimise IO performance but not decode performance?

This is a crock. I bet you'd be the first to complain if the p5p guys couldn't be bothered to consider the performance of the code they write.

I know my application's requirements, and with potentially, 2^47 states to explore, performance is crucial.

If you can't be bothered to make effective use of your users time, money and hardware by writing efficient code; why bother responding to a question clearly aimed at improving performance?

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.