Using the ILP64 Interface vs. LP64 Interface

Developer Guide

Contents

Using the ILP64 Interface vs. LP64 Interface

The
Intel® oneAPI Math Kernel Library
 ILP64 libraries use the 64-bit integer type (necessary for indexing large arrays, with more than 2
31
-1 elements), whereas the LP64 libraries index arrays with the 32-bit integer type.
The LP64 and ILP64 interfaces are implemented in the Interface layer. Link with the following interface libraries for the LP64 or ILP64 interface, respectively:
  • lib
    mkl_intel_lp64.
    a
     or
    lib
    mkl_intel_ilp64.
    a
     for static linking
  • lib
    mkl_intel_lp64
    .dylib
     or
    lib
    mkl_intel_ilp64
    .dylib
     for dynamic linking
The ILP64 interface provides for the following:
  • Support large data arrays (with more than 2
    31
    -1 elements)
  • Enable compiling your Fortran code with the
    -i
    8
     compiler option
The LP64 interface provides compatibility with the previous
Intel® oneAPI Math Kernel Library
 versions because "LP64" is just a new name for the only interface that the
Intel® oneAPI Math Kernel Library
 versions lower than 9.1 provided. Choose the ILP64 interface if your application uses
Intel® oneAPI Math Kernel Library
 for calculations with large data arrays or the library may be used so in the future.
Selected domains provide API extensions with the
_64
 suffix (for example,
SGEMM_64
) for supporting large data arrays in the LP64 library, which enables you to mix data types in one application:
  • BLAS: Fortran-style API for C applications only on 64-bit platform
  • LAPACK: Fortran-style API for C applications only on 64-bit platform
Intel® oneAPI Math Kernel Library
 provides the same include directory for the ILP64 and LP64 interfaces.

Compiling for LP64/ILP64

The table below shows how to compile for the ILP64 and LP64 interfaces:
Fortran
Compiling for ILP64
ifort
-i
8
-
I
<mkl directory>
/
include ...
Compiling for LP64
ifort
-
I
<mkl directory>
/
include ...
C or C++
Compiling for ILP64
ic
c
-
DMKL_ILP64
-
I
<mkl directory>
/
include ...
Compiling for LP64
ic
c
-
I
<mkl directory>
/
include ...
Linking of an application compiled with the
-i
8
 or
-
DMKL_ILP64
 option to the LP64 libraries may result in unpredictable consequences and erroneous output.

Coding for ILP64

You do not need to change existing code if you are not using the ILP64 interface.
To migrate to ILP64 or write new code for ILP64, use appropriate types for parameters of the
Intel® oneAPI Math Kernel Library
 functions and subroutines:
Integer Types
Fortran
C or C++
32-bit integers
INTEGER*4 or
INTEGER(KIND=4)
int
Universal integers for ILP64/LP64:
  • 64-bit for ILP64
  • 32-bit otherwise
INTEGER
 without specifying
KIND
MKL_INT
Universal integers for ILP64/LP64:
  • 64-bit integers
INTEGER*8
 or
INTEGER(KIND=8)
MKL_INT64
FFT interface integers for ILP64/LP64
INTEGER
 without specifying
KIND
MKL_LONG
To determine the type of an integer parameter of a function, use appropriate include files. For functions that support only a Fortran interface, use the C/C++ include files
*.h
.
The above table explains which integer parameters of functions become 64-bit and which remain 32-bit for ILP64. The table applies to most
Intel® oneAPI Math Kernel Library
 functions except some Vector Mathematics and Vector Statistics functions, which require integer parameters to be 64-bit or 32-bit regardless of the interface:
  • Vector Mathematics:
     The
    mode
     parameter of the functions is 64-bit.
  • Random Number Generators (RNG):
    All discrete RNG except
    viRngUniformBits64
     are 32-bit.
    The
    viRngUniformBits64
     generator function and
    vslSkipAheadStream
     service function are 64-bit.
  • Summary Statistics:
     The
    estimate
     parameter of the
    vslsSSCompute/vsldSSCompute
     function is 64-bit.
Refer to the
Intel® oneAPI Math Kernel Library
 Developer Reference
 for more information.
To better understand ILP64 interface details, see also examples.

Limitations

All
Intel® oneAPI Math Kernel Library
 function domains support ILP64 programming but FFTW interfaces to
Intel® oneAPI Math Kernel Library
:
  • FFTW 2.x wrappers do not support ILP64.
  • FFTW 3.x wrappers support ILP64 by a dedicated set of functions
    plan_guru64
    .

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.