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This page has a list of known issues for the Intel compilers (all versions).
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Intel compiler
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Use of MKL library can cause irreproducible results |
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OpenIFS includes a compilation configuration for the Intel compiler with the Intel MKL library (for optimized LAPACK/BLAS). However, please be aware use of this library can cause the model to be irreproducible, even on the same core count in successive runs. We recommend not using it if reproducibility is a concern. OpenIFS also only provides a compilation configuration for the MKL and the Intel library. Linking MKL with other compilers is possible, though complicated and is not tried or tested with OpenIFS. For help with linking the MKL library with other compilers, please see: https://software.intel.com/en-us/articles/intel-mkl-link-line-advisor |
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OpenIFS can fail with Intel compiler at -O2 |
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There is an issue with OpenIFS when compiling with the Intel compiler at optimization level -O2 or above on chipsets that support SSE4.1 & AVX instructions. Intel compilers are generally more aggressive at optimisations for -O2 than other compilers. Users will see failure with the T21 test job similar to the following:
It arises because this compiler makes use of 2-way vectorization when compiling both branches of IF statements which can generate floating point exceptions if a zero divide is possible in the unexecuted branch and the IFS internal signal handler (DRHOOK) is enabled. There are several possible workarounds:
OpenIFS uses a default of -O1 in the configuration files. If you increase the optimisation level, please be aware of this issue. For more help with this issue, please contact openifs-support@ecmwf.int. |
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OpenIFS fails writing GRIB if grib_api compiled with Intel and -O2 |
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We are aware of a problem in grib_api when using the Intel compiler that seems to affect different versions of grib_api and causes the model to fail with a floating point exception (SIGFPE). This is known to happen in the routine PRESET_GRIB_TEMPLATE or in the GRIB_F_SET_REAL8_ARRAY in the grib_api library. The advice is to reduce the optimization level when compiling grib_api to -O1 rather than -O2 or try a more recent version of the Intel compiler. The error message that typifies this problem is:
or a traceback like this:
Note that the grib packing can also fail if the model has produced fields with a very large range of values, such that the grib library can't pack the values into a smaller bit range. For further help, please contact openifs-support@ecmwf.int. |
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