- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

Consider this test program

```
use iso_fortran_env
write(*,'(g0)') 5.67e-14_real64
end
```

When compiled with "-assume old_e0g0_format", which is the default with ifx, I get something reasonable:

```
$ ifx -assume old_e0g0_format intel-20231213.f90
$ ./a.out
.5670000000000000E-13
```

But with "-assume noold_e0g0_format" which uses "F2018 formatting rules", I get this:

```
$ ifx -assume noold_e0g0_format intel-20231213.f90
$ ./a.out
.6E-13
```

That seems awfully extreme; there's not a single correct digit there. Can that possibly be valid?

I'll also note that "-standard-conforming" appears to imply "-assume noold_e0g0_format" even though the man page for ifx does not mention this one.

Link Copied

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

There is indeed a correct digit. The standard says, "Reasonable processor-dependent values of w, d (if not specified), and e are used with each output value." and "On output, with I, B, O, Z, F, and G editing, the specified value of the field width w may be zero. In such cases, the processor selects the **smallest positive actual field width that does not result in a field filled with asterisks.**" (emphasis mine).

The issue here, I think, is that someone at Intel took the latter part too seriously and didn't consider that a d of one was not "reasonable". I note that NAG's output is much the same as Intel's "old" output. I'd be curious to learn what prompted Intel to add this option.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

Thanks for your reply @Steve_Lionel . I can see now that what they've done is strictly okay: when Intel decides to write the number using an exponent, the smallest field width must include a single mantissa digit, and that's what they do (rounded correctly). 1.25d-2 is written ".1E-01". But funnily, 1.25d-1 is written without an exponent as ".1250000000000000", and so forth for larger values. I think Intel needs to seriously rethink how they've implemented this option, **which importantly is implied by -standard-semantics**, so they regard this as the proper standard behavior (and not a peculiar tweak) -- which for me makes g0 unusable.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

I agree.

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

Indeed (see j3-fortran.org/doc/year/21/21-172r1.txt) , but not for this case, where there are no changes.

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page