# Talk:Prime triangle

## An Observation

It may help some of the entries to note that primes greater than 2 are odd, and 1+1 is not valid, which implies that if you are looking for n+g=prime if a is even g must be odd and vv.--Nigel Galloway (talk) 10:44, 20 April 2022 (UTC)

- Yes. ... I can get a 30% speedup on the C implementation by changing
`for (size_t i = 1; i + 1 != length; ++i) {`to`for (size_t i = 1; i + 1 < length; i+= 2) {`.

- But I am leaving that alone for now -- this little laptop I am working on is so slow that the timings I would report would look like a significant slowdown even after that speedup (for me it's 1.64 seconds down to 1.25 seconds, and the code reports how long it takes to run). --Rdm (talk) 15:55, 21 April 2022 (UTC)

- Does seem to give a worthwhile performance boost, thanks Nigel - I've adjusted the VB.NET and Algol 68 samples accordingly. --Tigerofdarkness (talk) 18:27, 21 April 2022 (UTC)

- I've made this change to the C entry and a couple of my other ones. In the case of C++ and Swift (which is much slower than the others - about 12s?!) it made very little difference to the runtime so I've left them as is. --Simonjsaunders (talk) 21:29, 21 April 2022 (UTC)
- Also applied to Swift now, and I've made it much faster by not using ArraySlice. --Simonjsaunders (talk) 07:49, 22 April 2022 (UTC)

- I've made this change to the C entry and a couple of my other ones. In the case of C++ and Swift (which is much slower than the others - about 12s?!) it made very little difference to the runtime so I've left them as is. --Simonjsaunders (talk) 21:29, 21 April 2022 (UTC)