Add MPI+OpenMP hybrid parallelism (48 ranks x 2 threads) for full 96-core utilization

Enable OpenMP threading in finite-difference kernels (diff_new, diff_new_sh, diff_newwb,
lopsidediff, kodiss, kodiss_sh) with collapse(3) directives on 36 triple-nested loops.
Update build flags (-qopenmp), MPI process binding, and runtime configuration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

AMSS_NCKU_source/diff_new.f90

@@ -997,6 +997,7 @@
   fy = ZEO
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1151,6 +1152,7 @@
 
   fx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1227,6 +1229,7 @@
 
   fy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1297,6 +1300,7 @@
 
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1401,6 +1405,7 @@
   fxz = ZEO
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1576,6 +1581,7 @@
 
   fxx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1643,6 +1649,7 @@
 
   fyy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1712,6 +1719,7 @@
 
   fzz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1781,6 +1789,7 @@
 
   fxy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1851,6 +1860,7 @@
 
   fxz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1
@@ -1919,6 +1929,7 @@
 
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1

AMSS_NCKU_source/diff_new_sh.f90

@@ -1019,6 +1019,7 @@
   fy = ZEO
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1134,6 +1135,7 @@
 
   fx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1227,6 +1229,7 @@
 
   fy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1314,6 +1317,7 @@
 
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1430,6 +1434,7 @@
   fxz = ZEO
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1580,6 +1585,7 @@
 
   fxx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1659,6 +1665,7 @@
 
   fyy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1740,6 +1747,7 @@
 
   fzz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1821,6 +1829,7 @@
 
   fxy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1903,6 +1912,7 @@
 
   fxz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1983,6 +1993,7 @@
 
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)

AMSS_NCKU_source/diff_newwb.f90

@@ -1186,6 +1186,7 @@
   fy = ZEO
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1300,6 +1301,7 @@
 
   fx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1381,6 +1383,7 @@
 
   fy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1456,6 +1459,7 @@
 
   fz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1565,6 +1569,7 @@
   fxz = ZEO
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1781,6 +1786,7 @@
 
   fxx = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1856,6 +1862,7 @@
 
   fyy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -1933,6 +1940,7 @@
 
   fzz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -2010,6 +2018,7 @@
 
   fxy = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -2098,6 +2107,7 @@
 
   fxz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)
@@ -2184,6 +2194,7 @@
 
   fyz = ZEO
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)

AMSS_NCKU_source/kodiss.f90

@@ -159,6 +159,7 @@ integer, parameter :: NO_SYMM=0, OCTANT=2
 
   call symmetry_bd(3,ex,f,fh,SoA)
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)

AMSS_NCKU_source/kodiss_sh.f90

@@ -369,6 +369,7 @@ integer, parameter :: NO_SYMM=0, EQ_SYMM=1, OCTANT=2
 
   call symmetry_stbd(3,ex,f,fh,SoA)
 
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)
   do j=1,ex(2)
   do i=1,ex(1)

AMSS_NCKU_source/lopsidediff.f90

@@ -233,6 +233,7 @@ subroutine lopsided(ex,X,Y,Z,f,f_rhs,Sfx,Sfy,Sfz,Symmetry,SoA)
 
 ! upper bound set ex-1 only for efficiency,
 ! the loop body will set ex 0 also
+  !$omp parallel do collapse(3) private(i,j,k) if(ex(1)*ex(2)*ex(3) > 4096)
   do k=1,ex(3)-1
   do j=1,ex(2)-1
   do i=1,ex(1)-1

AMSS_NCKU_source/makefile.inc

@@ -7,19 +7,18 @@
 filein  = -I/usr/include/ -I${MKLROOT}/include
 
 ## Using sequential MKL (OpenMP disabled for better single-threaded performance)
-LDLIBS  = -L/usr/lib/x86_64-linux-gnu -L/usr/lib64 -lifcore -limf -lmpi \
-          -L${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_sequential -lmkl_core \
-          -lpthread -lm -ldl
+## Added -lifcore for Intel Fortran runtime and -limf for Intel math library
+LDLIBS  = -L${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lifcore -limf -lpthread -lm -ldl -qopenmp
 
 ## Aggressive optimization flags:
 ## -O3: Maximum optimization
 ## -xHost: Optimize for the host CPU architecture (Intel/AMD compatible)
 ## -fp-model fast=2: Aggressive floating-point optimizations
 ## -fma: Enable fused multiply-add instructions
-## Note: OpenMP has been disabled (-qopenmp removed) due to performance issues
-CXXAPPFLAGS  = -O3 -xHost -fp-model fast=2 -fma \
+## OpenMP re-enabled for MPI+OpenMP hybrid parallelism (MKL stays sequential to avoid nested parallelism)
+CXXAPPFLAGS  = -O3 -xHost -fp-model fast=2 -fma -qopenmp \
                -Dfortran3 -Dnewc -I${MKLROOT}/include
-f90appflags  = -O3 -xHost -fp-model fast=2 -fma \
+f90appflags  = -O3 -xHost -fp-model fast=2 -fma -qopenmp \
                -fpp -I${MKLROOT}/include
 f90          = ifx
 f77          = ifx

makefile_and_run.py

@@ -13,13 +13,9 @@ import subprocess
 
 ## CPU core binding configuration using taskset
 ## taskset ensures all child processes inherit the CPU affinity mask
-## This forces make and all compiler processes to use only nohz_full cores (4-55, 60-111)
-## Format: taskset -c 4-55,60-111 ensures processes only run on these cores
-NUMACTL_CPU_BIND = "taskset -c 4-55,60-111"
+NUMACTL_CPU_BIND = "taskset -c 0-111"
 
 ## Build parallelism configuration
-## Use nohz_full cores (4-55, 60-111) for compilation: 52 + 52 = 104 cores
-## Set make -j to utilize available cores for faster builds
 BUILD_JOBS = 104
 
 
@@ -114,12 +110,18 @@ def run_ABE():
     print(                                                      )
 
     ## Define the command to run; cast other values to strings as needed
+    ## MPI+OpenMP hybrid: compute threads per rank from total cores / MPI ranks
+    omp_threads = max(1, 96 // input_data.MPI_processes)
+    omp_env = (f" -genv OMP_NUM_THREADS={omp_threads}"
+               f" -genv OMP_PROC_BIND=close"
+               f" -genv OMP_PLACES=cores"
+               f" -genv I_MPI_PIN_DOMAIN=omp")
 
     if (input_data.GPU_Calculation == "no"):
-        mpi_command         = NUMACTL_CPU_BIND + " mpirun -np " + str(input_data.MPI_processes) + " ./ABE"
+        mpi_command         = NUMACTL_CPU_BIND + " mpirun -np " + str(input_data.MPI_processes) + omp_env + " ./ABE"
         mpi_command_outfile = "ABE_out.log"
     elif (input_data.GPU_Calculation == "yes"):
-        mpi_command         = NUMACTL_CPU_BIND + " mpirun -np " + str(input_data.MPI_processes) + " ./ABEGPU"
+        mpi_command         = NUMACTL_CPU_BIND + " mpirun -np " + str(input_data.MPI_processes) + omp_env + " ./ABEGPU"
         mpi_command_outfile = "ABEGPU_out.log"
  
     ## Execute the MPI command and stream output