Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

  • Congratulations strongm on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!

Auto-parallelized code runs, but why no speedup?

Status
Not open for further replies.

FiascoBurnett

Programmer
May 25, 2015
6
ZA
I have a working program (Fortran 77) that I’m trying to auto-parallelize on a cluster. The changes made in the compiling makefiles (abbreviated) are shown in the curly brackets below.
Build library:
FOR=ifort -c -O3 {-parallel}
LINK=ifort {-parallel}
PROG_DIR=/export/home/mydir/
HJS=$(PROG_DIR)/hjs
.f.o:
$(FOR) $<
rm libprog.a
$(FOR) $(HJS)/*.f
ar -rv $(PROG_DIR)/libprog.a *.o
rm *.o
Compile executable:
FOR=ifort -c -O3 {-parallel}
LINK=ifort {-parallel}
PROG_DIR=/export/home/mydir/
LIBPROG=-L$(PROG_DIR) -lprog
.f.o:
$(FOR) $(OPT) $<
prog_hjs.o: prog_hjs.f
$(FOR) prog_hjs.f
prog_hjs: prog_hjs.o
$(LINK) -o prog_hjs prog_hjs.o $(LIBPROG)
The program appears to utilize as many cores as are given to it, but execution speed is unchanged. What is missing? Is anything more required in the compilation above?
 
Impossible to say without examing the code.

But in general, it is better to implement yourself parallel instructions using OpenMP for instance. This is much more efficient than automatic parallelization. But this is not easy to do.

François Jacq
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor

Back
Top