I am using the gcc compiler and I am new to using flags.
Can any one tell me a source for it.
e.g. I wanted to use -funroll-loops but I dont know the proper syntax. Can any one help.

The usual place to look for options to a program are the man pages of that program. Typeing man gcc at the command prompt will give you a good start.

I just cant figure out the syntax.

gcc -O2 -funroll-loops -dgemm-blocked.c

optimazation Level flag name file name

What am I missing?

A space between the flag and the file name.