GCC Optimization Levels - Seeking Insights

[Aran Nokan via Gcc-help <gcc-help@xxxxxxxxxxx>]

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?


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