Hi, Thank you. I noticed that it is not working with the following error: No rule to make target 'test.0', So I changed it to this: $(PROGS): test.% : $(SRC) $(DEPS) > $(CC) -o $@ $(CFLAGS) $(LDLAGS) -O$* $(SRC) But now another problem: make: *** No rule to make target 'levmarg.c', needed by 'test.0'. Stop. > Do you have any idea how to fix it? Sincerely, Aran On Fri, Dec 22, 2023 at 10:26 AM David Brown via Gcc-help < gcc-help@xxxxxxxxxxx> wrote: > On 21/12/2023 20:57, Jonathan Wakely via Gcc-help wrote: > > On Thu, 21 Dec 2023, 19:33 Aran Nokan via Gcc-help, < > gcc-help@xxxxxxxxxxx> > > wrote: > > > >> Hello GCC Community, > >> > >> I recently conducted an experiment where I tested the impact of > different > >> GCC optimization levels on the performance of a code > >> <https://github.com/leechwort/levenberg-maquardt-example>. I observed > that > >> higher optimization levels didn't necessarily result in faster code > >> execution. > >> > >> Is it correct or I have made a mistake? Do we have any other parameters > for > >> optimization? > >> > > > > There is no guarantee that optimization make code faster, except that -O0 > > will invariably be slower. > > > > > > However, I suspect the problem is that your makefile only builds the .o > > objects once, for the first target that needs them. That means they will > be > > optimized (or not optimized) according to the CFLAGS set when building > that > > first target. > > > > Unless you do 'make clean' before building each target, you weren't > > actually testing what you intend to test. > > > > > > For this test, since there are not many source files, I'd put them all > on the same gcc line : > > > default: all > .PHONY: all > > > OPTS = 0 1 2 3 g fast > > PROGS = $(foreach opt, $(OPTS), test.$(opt)) > all: $(PROGS) > > CC = gcc > CFLAGS_COMMON = -I. > LDLAGS = -lm > DEPS = levmarq.h makefile > SRC = main.c levmarg.c > > test.% : $(SRC) $(DEPS) > gcc -o $@ $(CFLAGS) $(LDLAGS) -O$* $(SRC) > > clean: > rm -f $(PROGS) > > > > (I haven't tried the makefile at all, but it might be a starting point > for the OP.) > > > >> > >> My make file was as follows: > >> > >> > >> CC=gcc > >>> CFLAGS_COMMON=-I. > >>> LDLAGS=-lm > >>> DEPS = levmarq.h > >>> OBJ = main.o levmarq.o > >>> > >>> %.o: %.c $(DEPS) > >>> $(CC) -c -o $@ $< $(CFLAGS) $(LDLAGS) > >>> > >>> main: $(OBJ) > >>> gcc -o $@ $^ $(CFLAGS) $(LDLAGS) > >>> > >>> # No optimization > >>> main_no_opt: CFLAGS += -O0 > >>> main_no_opt: $(OBJ) > >>> gcc -o $@ $^ $(CFLAGS) $(LDLAGS) > >>> > >>> # Basic optimization > >>> main_opt1: CFLAGS += -O1 > >>> main_opt1: $(OBJ) > >>> gcc -o $@ $^ $(CFLAGS) $(LDLAGS) > >>> > >>> # Moderate optimization > >>> main_opt2: CFLAGS += -O2 > >>> main_opt2: $(OBJ) > >>> gcc -o $@ $^ $(CFLAGS) $(LDLAGS) > >>> > >>> # High optimization > >>> main_opt3: CFLAGS += -O3 > >>> main_opt3: $(OBJ) > >>> gcc -o $@ $^ $(CFLAGS) $(LDLAGS) > >>> > >>> # Clean rule > >>> clean: > >>> rm -f *.o main main_no_opt main_opt2 main_opt3 > >>> > >> > >> Best regards, > >> Aran > >> > > > > >
