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High Performance Scientific Computing
AMath 483/583 Class Notes Spring Quarter, 2013 |
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High Performance Scientific Computing
AMath 483/583 Class Notes Spring Quarter, 2013 |
The directory $UWHPSC/codes/fortran/multifile1 contains a Fortran code fullcode.f90 that consists of a main program and two subroutines:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | ! $UWHPSC/codes/fortran/multifile1/fullcode.f90
program demo
print *, "In main program"
call sub1()
call sub2()
end program demo
subroutine sub1()
print *, "In sub1"
end subroutine sub1
subroutine sub2()
print *, "In sub2"
end subroutine sub2
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To illustrate the construction of a Makefile, we first break this up into three separate files:
1 2 3 4 5 6 7 | ! $UWHPSC/codes/fortran/multifile1/main.f90
program demo
print *, "In main program"
call sub1()
call sub2()
end program demo
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1 2 3 4 5 | ! $UWHPSC/codes/fortran/multifile1/sub1.f90
subroutine sub1()
print *, "In sub1"
end subroutine sub1
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1 2 3 4 5 | ! $UWHPSC/codes/fortran/multifile1/sub2.f90
subroutine sub2()
print *, "In sub2"
end subroutine sub2
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The directory $UWHPSC/codes/fortran/multifile1 contains several Makefiles that get successively more sophisticated to compile the codes in this directory.
In the first version we write out explicitly what to do for each file:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | # $UWHPSC/codes/fortran/multifile1/Makefile
output.txt: main.exe
./main.exe > output.txt
main.exe: main.o sub1.o sub2.o
gfortran main.o sub1.o sub2.o -o main.exe
main.o: main.f90
gfortran -c main.f90
sub1.o: sub1.f90
gfortran -c sub1.f90
sub2.o: sub2.f90
gfortran -c sub2.f90
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In the second version there is a general rule for creating .o files from .f90 files:
1 2 3 4 5 6 7 8 9 10 | # $UWHPSC/codes/fortran/multifile1/Makefile2
output.txt: main.exe
./main.exe > output.txt
main.exe: main.o sub1.o sub2.o
gfortran main.o sub1.o sub2.o -o main.exe
%.o : %.f90
gfortran -c $<
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In the third version we define a macro OBJECTS so we only have to write out this list once, which minimizes the chance of introducing errors:
1 2 3 4 5 6 7 8 9 10 11 12 | # $UWHPSC/codes/fortran/multifile1/Makefile3
OBJECTS = main.o sub1.o sub2.o
output.txt: main.exe
./main.exe > output.txt
main.exe: $(OBJECTS)
gfortran $(OBJECTS) -o main.exe
%.o : %.f90
gfortran -c $<
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In the fourth version, we add a Fortran compile flag (for level 3 optimization) and an linker flag (blank in this example):
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | # $UWHPSC/codes/fortran/multifile1/Makefile4
FC = gfortran
FFLAGS = -O3
LFLAGS =
OBJECTS = main.o sub1.o sub2.o
output.txt: main.exe
./main.exe > output.txt
main.exe: $(OBJECTS)
$(FC) $(LFLAGS) $(OBJECTS) -o main.exe
%.o : %.f90
$(FC) $(FFLAGS) -c $<
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Next we add a phony target clean that removes the files created when compiling the code in order to facilitate cleanup. It is phony because it does not create a file named clean.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | # $UWHPSC/codes/fortran/multifile1/Makefile5
OBJECTS = main.o sub1.o sub2.o
.PHONY: clean
output.txt: main.exe
./main.exe > output.txt
main.exe: $(OBJECTS)
gfortran $(OBJECTS) -o main.exe
%.o : %.f90
gfortran -c $<
clean:
rm -f $(OBJECTS) main.exe
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Finally we add a help message so that make help says something useful:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | # $UWHPSC/codes/fortran/multifile1/Makefile6
OBJECTS = main.o sub1.o sub2.o
.PHONY: clean help
output.txt: main.exe
./main.exe > output.txt
main.exe: $(OBJECTS)
gfortran $(OBJECTS) -o main.exe
%.o : %.f90
gfortran -c $<
clean:
rm -f $(OBJECTS) main.exe
help:
@echo "Valid targets:"
@echo " main.exe"
@echo " main.o"
@echo " sub1.o"
@echo " sub2.o"
@echo " clean: removes .o and .exe files"
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Fancier things are also possible, for example automatically detecting all the .f90 files in the directory to construct the list of SOURCES and OBJECTS:
1 2 3 4 5 6 7 8 9 10 | # $UWHPSC/codes/fortran/multifile1/Makefile7
SOURCES = $(wildcard *.f90)
OBJECTS = $(subst .f90,.o,$(SOURCES))
.PHONY: test
test:
@echo "Sources are: " $(SOURCES)
@echo "Objects are: " $(OBJECTS)
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