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30-Dec-20 8:06

In looking at this JPL/Nasa code, it makes references to doing this and that for "performance".

In some cases, their loop variable is an int; in others a short; in others a long.

Given a choice which is best?

Probably an int, unless you "need" a long.

Ironic that for the sake of "storage" (2 bytes), they've sacrificed performance.

asp.net - Why should I use int instead of a byte or short in C# - Stack Overflow

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

C^hris L^osinger30-Dec-20 8:12

30-Dec-20 8:12

what does the compiler turn those into and what's the CPU word size?

Gerry Schmitz30-Dec-20 8:20

30-Dec-20 8:20

You mean it might be code that assumes a particular multi-platform optimizing compiler?

And only if the index has no other function than to "iterate"?

And refactoring is not an option?

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

C^hris L^osinger30-Dec-20 8:24

30-Dec-20 8:24

I mean: where does the code in question run? And what does the compiler generate, and how does that mesh with the target CPU?

If it's hardware that's going to space, it's probably not running on a common commercial CPU, so you can't make assumptions about word size and what a 'short' is, etc..

[I don't actually know which code you're talking about]

Gerry Schmitz wrote:
And refactoring is not an option?

if it's commented as being there for performance reasons, you can probably assume it was profiled and tested for performance.

Gerry Schmitz30-Dec-20 8:35

30-Dec-20 8:35

You make a lot of assumptions.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

C^hris L^osinger30-Dec-20 8:39

30-Dec-20 8:39

WTF.

if you don't know anything about the hardware that runs it, you can't make assumptions about the software.

Gerry Schmitz30-Dec-20 8:51

30-Dec-20 8:51

It can run on anything with a C compiler. I could put it on my phone / watch.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

C^hris L^osinger30-Dec-20 9:01

30-Dec-20 9:01

maybe it can run on anything with a C compiler ... as long as it was deliberately written to work on any OS with any CRT implementation, using no system-specific libraries, and making no assumptions about the underlying hardware. Laugh | :laugh:

the C spec only specifies minimum sizes for short, int and long. int and short must be at least 16 bits. long must be at least 32 bits.

so what any of those types means in terms of storage and CPU handling (aka performance) depends on the compiler and the target architecture.

Gerry Schmitz30-Dec-20 9:11

30-Dec-20 9:11

They've built a Python shell for it. Does that help or confuse?

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

obermd31-Dec-20 6:19

obermd

31-Dec-20 6:19

No, your assessment that they're making an invalid tradeoff is the assumption. JPL writes real-time code for memory limited systems that cannot fail. Their use case is far different from almost everyone else.

rnbergren30-Dec-20 8:16

rnbergren

30-Dec-20 8:16

When is the code from? There are times were storage does matter alot more than performance. And in the past for NASA they had some very strict storage requirements. I can see this being a huge discussion at the code review.

Interesting to say the least.

Me no, I never really think about it. I almost always use an int and move on with life.

To err is human to really elephant it up you need a computer

Slacker00730-Dec-20 8:26

Slacker007

30-Dec-20 8:26

rnbergren wrote:
I never really think about it. I almost always use an int and move on with life.

exactly.

Gerry Schmitz30-Dec-20 8:34

30-Dec-20 8:34

"Not thinking" is not something I ever boasted about. It was a thought exercise; regardless of what the compiler "might do".

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Slacker00730-Dec-20 9:33

Slacker007

30-Dec-20 9:33

an int is just fine. for me, it is a no brainer. If you want to spend hours thinking about it, go for it.

Gerry Schmitz30-Dec-20 8:28