Contents of /MITgcm_contrib/cg2d_bench/README

#	$Id$	
Benchmarking routine of the CG2D solver in MITgcm (barotropic solve)

To build:

a) Parameterization of SIZE.h:
sNx = size of tile in x-direction (ideally fits in cache, 30-60)
sNy = size of tile in y-direction (ideally fits in cache, 30-60)
OLx = overlap size in x-direction (1 or 3 usually)
OLy = overlap size in y-direction (1 or 3 usually)
b) Compilation
$CC $CFLAGS -c tim.c
$FC $DEFINES $INCLUDES $FCFLAGS -o cg2d *.F tim.o $LIBS -lm

$DEFINES:
1) For single precision add
-DUSE_SINGLE_PRECISION
2) For mixed (single for most ops, double for reductions) precision add
-DUSE_MIXED_PRECISION to -DUSE_SINGLE_PRECISION
3) Parallel (MPI) operation
-DALLOW_MPI -DUSE_MPI_INIT -DUSE_MPI_GSUM -DUSE_MPI_EXCH
4) Use MPI timing routines
-DUSE_MPI_TIME
5) Use of MPI_Sendrecv() instead of MPI_Isend/MPI_Irecv()/MPI_Waitall()
-DUSE_SNDRCV
6) Use of JAM for exchanges (not available without the hardware)
-DUSE_JAM_EXCH
7) Use of JAM for the global sum (not available without the hardware)
-DUSE_JAM_GSUM
8) In order to avoid doing the global sum in MPI do not define
-DUSE_MPI_GSUM
and all processors will see their own residual instead (dangerous)
9) In order to avoid doing the exchanges in MPI do not define
-DUSE_MPI_EXCH
and all processors avoid exchanging shadow regions (dangerous)
10) Performance counters
-DUSE_PAPI_FLOPS	To use PAPI to produce Mflop/s
or
-DUSE_PAPI_FLIPS	To use PAPI to produce Mflip/s
To produce this information for every iteration instead of each "timestep" 
add a -DPAPI_PER_ITERATION to the above
11) Extra (nearest neighbor) exchange steps to stress comms
-DTEN_EXTRA_EXCHS
12) Extra (global) sum steps to stress comms
-DHUNDRED_EXTRA_SUMS
13) 2D (PxQ) vs 1D decomposition
-DDECOMP2D
14) To output the residual every iteration:
-DRESIDUAL_PER_ITERATION

$INCLUDES (if using PAPI)
-I$PAPI_ROOT/include

$LIBS (if using PAPI - depending on the platform extra libs may be needed)
-L$PAPI_ROOT/lib -lpapi

c) Running

1) Allowing the system to choose the PxQ decomposition if setup for it:
mpiexec -n $NPROCS ./cg2d
2) Create a decomp.touse with the P & Q dimensions declared in the first
two lines as two integers, eg.

cat > decomp.touse << EOF
10
20
EOF

mpiexec -n 200 ./cg2d
1	# $Id$
2	Benchmarking routine of the CG2D solver in MITgcm (barotropic solve)
3
4	To build:
5
6	a) Parameterization of SIZE.h:
7	sNx = size of tile in x-direction (ideally fits in cache, 30-60)
8	sNy = size of tile in y-direction (ideally fits in cache, 30-60)
9	OLx = overlap size in x-direction (1 or 3 usually)
10	OLy = overlap size in y-direction (1 or 3 usually)
11	b) Compilation
12	$CC $CFLAGS -c tim.c
13	$FC $DEFINES $INCLUDES $FCFLAGS -o cg2d *.F tim.o $LIBS -lm
14
15	$DEFINES:
16	1) For single precision add
17	-DUSE_SINGLE_PRECISION
18	2) For mixed (single for most ops, double for reductions) precision add
19	-DUSE_MIXED_PRECISION to -DUSE_SINGLE_PRECISION
20	3) Parallel (MPI) operation
21	-DALLOW_MPI -DUSE_MPI_INIT -DUSE_MPI_GSUM -DUSE_MPI_EXCH
22	4) Use MPI timing routines
23	-DUSE_MPI_TIME
24	5) Use of MPI_Sendrecv() instead of MPI_Isend/MPI_Irecv()/MPI_Waitall()
25	-DUSE_SNDRCV
26	6) Use of JAM for exchanges (not available without the hardware)
27	-DUSE_JAM_EXCH
28	7) Use of JAM for the global sum (not available without the hardware)
29	-DUSE_JAM_GSUM
30	8) In order to avoid doing the global sum in MPI do not define
31	-DUSE_MPI_GSUM
32	and all processors will see their own residual instead (dangerous)
33	9) In order to avoid doing the exchanges in MPI do not define
34	-DUSE_MPI_EXCH
35	and all processors avoid exchanging shadow regions (dangerous)
36	10) Performance counters
37	-DUSE_PAPI_FLOPS To use PAPI to produce Mflop/s
38	or
39	-DUSE_PAPI_FLIPS To use PAPI to produce Mflip/s
40	To produce this information for every iteration instead of each "timestep"
41	add a -DPAPI_PER_ITERATION to the above
42	11) Extra (nearest neighbor) exchange steps to stress comms
43	-DTEN_EXTRA_EXCHS
44	12) Extra (global) sum steps to stress comms
45	-DHUNDRED_EXTRA_SUMS
46	13) 2D (PxQ) vs 1D decomposition
47	-DDECOMP2D
48	14) To output the residual every iteration:
49	-DRESIDUAL_PER_ITERATION
50
51	$INCLUDES (if using PAPI)
52	-I$PAPI_ROOT/include
53
54	$LIBS (if using PAPI - depending on the platform extra libs may be needed)
55	-L$PAPI_ROOT/lib -lpapi
56
57	c) Running
58
59	1) Allowing the system to choose the PxQ decomposition if setup for it:
60	mpiexec -n $NPROCS ./cg2d
61	2) Create a decomp.touse with the P & Q dimensions declared in the first
62	two lines as two integers, eg.
63
64	cat > decomp.touse << EOF
65	10
66	20
67	EOF
68
69	mpiexec -n 200 ./cg2d