Initialization fails all the time

[Former user]

Hello, Nathanael,

I have sucessfully compiled the fortran example code "SHT_example.f", but when I run it, I always get the following output. It seems the initialization fails due to bad SHT accuracy. I compiled the example code using Intel fortran compiler 15 with options: -lshtns_omp -lfftw3_omp -lm -lrt. My system is Linux 64 bit. Please help me identify the problem. Thank you for providing such a great library!

 NLM=          12
[SHTns 2.6.5] built Jun 28 2016, 15:50:25, id: avx
        Lmax=5, Mmax*Mres=4, Mres=2, Nlm=12  [3 threads, orthonormalized]
        => using FFTW : Mmax=2, Nphi=6, Nlat=8  (data layout : phi_inc=1, theta_inc=6, phi_embed=6)
        => using Gauss nodes
        + polar optimization threshold = 1.0e-10
        + SHT accuracy = 0.214
Lmax=5, Mmax*Mres=4, Mres=2, Nlm=12  [3 threads, orthonormalized]
Gauss grid : Nlat=8, Nphi=6
        syn   ana   vsy   van   gsp   gto   v3s   v3a 
   std:  mem   mem   mem   mem   mem   mem   mem   mem 
   ltr:  mem   mem   mem   mem   mem   mem   mem   mem 
     m: none  none  none  none  none  none  none  none 
*** [SHTns] Run-time error : bad SHT accuracy

[Nathanaël Schaeffer]

Hello,

I have been able to reproduce the bug. It happens only when the intel compilers are used together with OpenMP. If you use gcc / gfortran, or if you disable openmp, it works well.

I will need to investigate this issue further

[Nathanaël Schaeffer]

After more investigation, it appears to me as a compiler bug:

• It does not happen with gcc/gfortran
• It does not happen with icc/ifort 14
• It does not happen without -fopenmp
• It does not happen without optimizations ( -O0 )

Suggested workaround : in the Makefile, replace the line

cc = $(CC) $(go) -O2

with

 cc = $(CC) $(go) -O0

It will slow down the initialization process a bit, but not the actual transforms. Please confirm that this fixes the problem for you too.

[plw0315]

Hello,

Thanks for your quick reply and through investigation! Since I use your library on a computer cluster managed by my university, I am not able to reinstall your library with a different compiler. Today is a holiday (US independent day) here, I have to wait tomorrow and ask the cluster technician to reinstall it. For your suggestions about openmp and optimizations, I did the following tests:

For system Linux 64 bit and compiler ifort 15 with options: -lfftw3_omp -lshtns_omp -lm –lrt:

1) The problem remains with or without option -openmp.

2) The problem remains with any optimization from -o0 to -o3.

I will update again when I have a change to test the example code with a different compiler. Thanks again.

[plw0315]

Hello,

The fortran example code "SHT_example.f" works properly when compiled with ifort 13, but not with ifort 15 or 16. The fortran compiler ifort 14 and gfortran has not been tested. Thanks for your help!

[plw0315]

Hello again,

You are right about Intel compiler 15, if I one followed the workaround as you suggested and change the line in the makefile:

cc = $(CC) $(go) -O2

to

cc = $(CC) $(go) -O0

The example fortran code will work properly. I think this issue has been solved. Thank you very much!