Can nvfortran handle large direct access I/O?

Accelerated Computing HPC Compilers nvc, nvc++ and nvfortran
1

Hello,

We ran into a problem with the nvfortran compiler (version 21.7). It appears that nvfortran fails to handle Fortran direct access I/O when the record length (recl) exceeds the maximum value of a 32-bit integer. I created a mini reproducer here: GitHub - vyu16/test_direct_io

gfortran worked:

$ gfortran --version
GNU Fortran (GCC) 11.2.0
Copyright (C) 2021 Free Software Foundation, Inc.

$ gfortran -o test.x test.f90 
$ ./test.x 
  record length should be:          19110297600
  record length returned by inquire:          19110297600
  record length in file:          19110297600

nvfortran failed:

$ nvfortran --version
nvfortran 21.7-0 64-bit target on x86-64 Linux -tp zen 
NVIDIA Compilers and Tools
Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES.  All rights reserved.

$ nvfortran -o test.x test.f90
$ ./test.x 
  record length should be:              19110297600
  record length returned by inquire:                        3
  record length in file:                        3
  cannot write, error:          219

Am I missing a compiler flag or something? Or is this currently not supported by nvfortran?

Thank you for your help!

Victor

2

I suspect we don’t support record lengths > 2 GB. I will do a little more research and check with engineering.

3

I think another problem is with that form of the inquire statement. It should return a default integer, but even if I compile with -i8, it doesn’t seem to return a valid 8-byte value.

4

Thank you for investigating! Indeed, inquire doesn’t seem to return the correct value. We just replaced all “direct” with “stream” in our code we. Everything is working now. Would be great to have “direct” working in future releases of nvfortran!

Thanks,
Victor

5

I opened an RFE for this, FS#30769. It would have to be an opt-in, as the record length is a part of the file format, and changing that would break existing direct i/o to existing files. But, might be something to consider with Flang/F18. I know we have tried to be compatible with Intel; sounds like we are not with gfortran.

6

Dear Brent,

I was bitten by this again … Wasted an hour debugging my code only to realize that it’s the same issue. Is there any update on this? I checked the man page of nvfortran 23.5 and didn’t seem to see anything relevant.

Thanks,
Victor

7

Hi Victor,

I took a look at the report and this has been assigned to the Flang team so not something we’ll add to nvfortran. Since we’ll eventually replace nvfortran with our version of Flang, new features requests are being directed there.

-Mat