9. Migration from other systems

9.1. Overview

Here indicates about main compile option which is incompatible when migrating the program from other Fujitsu system (PC cluster and Supercomputer K) to Supercomputer Fugaku and other company’s compiler (Intel compiler and gcc).

9.2. Migration from K

Here indicates main difference between Supercomputer Fugaku and Supercomputer K.

Item	K	Fugaku	Note
Executable file	SPARC VIIIfx format	Armv8.2-A format	Incompatible. Re-compile is required.
Staging	Yes	No
Recommended number of process in node	1	4	Due to having 4 CMG (Core Memory Group, NUMA node) in 1 node
Maximum number of thread in node	8	48	12 thread/process when 4 process/node
Large page	4MiB/32MiB/256MiB	4MiB
Endian	Big endian	Little Endian	Incompatible on binary data
Language environment setting direction	Uses Env_base file	Uses Environment Modules	Default environment is loaded when logging in and job execution

Please refer to “14. Migration from K” of “Supercomputer Fugaku Users Guide -Language and development environment- “ about main incompatible of language environment.

Based on the difference in above, we indicate the change example of job script in below.

[Supercomputer K job script example]

#!/bin/sh -x
#PJM --rsc-list  "node=8"                   # Number of assign node 8  (1 dementional format)
#PJM --rsc-list  "elapse=01:00:00"          # Running time limit 1 hour
#PJM --stg-transfiles all
#PJM --mpi "use-rankdir"                    # Rank number directory use declaration
#PJM --stgin "rank=* ./a.out %r:./"         # Stage in ./a.out to each rank
#PJM -s                                     # Output statistic information
#
. /work/system/Env_base                     # Set environment variables
#
export OMP_NUM_THREADS=8
mpiexec -n 8 ./a.out    # Execute a.out

Change job script as following.

• Delete the definition about staging (–stg-transfiles, use-rankdir, –stgin, –stgout etc). If definition is still existing, nothing works.

• Since 1node 4 process, it is using max-proc-per-node=4 here.

• To make number of process to 8, change number of node to 2. If number of node is 8, it executes with 32 process.

• Since default language environment is set when job execution, delete environment variables setting.

[Supercomputer Fugaku job script example]

#!/bin/sh -x
#PJM --rsc-list  "node=2"                   # Number of assign node 2 (1 dementional format)
#PJM --rsc-list  "elapse=01:00:00"          # Running time limit 1 hour
#PJM --mpi max-proc-per-node=4              # Upper limit of number of MPI process that created at 1 node
#PJM -g groupname                         # group name
#PJM -x PJM_LLIO_GFSCACHE=/vol000N          # volume names that job uses
#PJM -s                                     # Output statistic information
#

export OMP_NUM_THREADS=12
mpiexec -n 8 ./a.out    # Execute a.out

When executing a job, the directory where pjsub is executed operates as the current directory of the job. When executing multiple jobs at the same time, make sure that input / output data does not conflict between jobs.

9.3. Migration from other Fujitsu systems

This indicates about the migration from other Fujitsu systems, compile option and the difference of optimization directive.

9.3.1. Option difference

Here indicates representative option because of migration from other systems.

PC cluster	“K”	FX100	Fugaku	Changed point
-Kfast	-Kfast	-Kfast	-Kfast
-Kparallel	-Kparallel	-Kparallel	-Kparallel
-Kopenmp	-Kopenmp	-Kopenmp	-Kopenmp
None	-KXFILL	-KXFILL	-Kzfill	Changed option name at “Fugaku”
None	-Kuxsimd	-Kuxsimd	None	Abolished option at “Fugaku”
-Kopenmp_tls	-Kopenmp_tls	-Kopenmp_tls	None	Abolished option at “Fugaku”

9.3.2. Optimization indicator (OCL) difference

Here indicates added to changed representative OCL.

PC cluster	“K”	FX100	Fugaku	Changed point
None	XFILL	XFILL	ZFILL	Name changed at “Fugaku”
None	UXSIMD	UXSIMD	None	Abolished at “Fugaku”

9.4. Migration from other systems

Here indicates main option difference about Intel compiler and GNU.

Item	Induces optimisation option for speeding up	Automatic parallel	OpenMP	Change local variables to automatic variables
Supercomputer Fugaku	-Kfast	-Kparallel	-Kopenmp	-Kauto
Intel compiler	-O3 -xHost	-parallel	-openmp	-auto
GNU	-O3	-	-fopenmp	-

See also

1. If change to fccpx from GCC (gcc)

   In addition to fccpx, C11 specification understand based on GNU C extentional specification.
2. If change to fccpx from Intel compiler (ifort)
   Display option to extend Fortran fixed specification.

   Supercomputer Fugaku:-Fwide(Up to 255 letters)

   Intel compiler :-132

9.5. Endian

Here explains about Endian and about comparing with Supercomputer K and target compilers.

9.5.1. Overview

At Supercomputer K, Big Endian is used. On the other hands, Supercomputer Fugaku and around devices uses Little Endian.

Indicates Endian used on each node.

Endian on each node

Node type	K	Fugaku
Computing node	Big Endian	Little Endian
Login node	Little Endian	Little Endian

It is required to change Endian to use the binary data that is created with Supercomputer K. Indicates the policy of change at Data migration (change) policy .

Data migration (change) policy

Language	Change direction
Fortran (Input and output without style)	Uses language software change function
Fortran(Other)	Change by the user
C	Change by the user
C++	Change by the user
MPI-IO	Change by the user

9.5.2. Target compiler

The target compiler in this section is as following. On these compilers, Some Endian conversion functions are provided for Fortran binary data.

9.5.2.1. Fujitsu compiler

At Fujitsu compiler, execution option and change command are offered.

Function	Explanation
Execution option	By putting -Wl,-T to the execution option of Fortran program, Endian change is exeuted when Fortran input/output.
Change command	Offeres fcvendianpx command. Use as fcvendianpx inputfilename outputfilename typetype specifies data type to change (one of these values: 2, 4, 8, 16).

9.5.2.2. Intel compiler

At Intel compiler, compile option and environment variables when execution are offered.

Function	Explanation
Compile option	By compiling with putting -convert big_endian , -convert little_endian, it is possible to make numeric data format without style to Big Endian or Little Endian.
Environment variables when execution	Specify environment variables F_UFMTENDIAN = MODE (MODE = big | little).

9.5.2.3. GNU compiler(GCC)

At gfortran, convert specifier by extending the OPEN statement and execution option are offered.

Function	Explanation
OPEN statement’s extention	Specify CONVERT='BIG_ENDIAN' and CONVERT='LITTLE_ENDIAN' to OPEN statement. Specify such as open(file='big.dat',form='unformatted', convert='big_endian').
Execution option	Specify -fconvert=big-endian and -fconvert=little-endian.