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42 Cray T3E User’s Guide
File extension Type Notes
.f Fixed source form (72 columns) No preprocessing
.f90 Free source form (132 columns) No preprocessing
.F Fixed source form (72 columns) Preprocessing
.F90 Free source form (132 columns) Preprocessing
.o Object file Passed to linker
.a Object library file Passed to linker
.s Assembly language file Passed to assembler
Table 5.1: The interpretation of some filename extensions.
5.4 Compiler options
You can control the compilation process using compiler options. The
most common situation is to increase the optimization level. The fol-
lowing command sequence illustrates a typical compilation process and
creation of an executable (master.x). The source code is in the files
master.f90 and shallow.f90.
t3e% f90 -c master.f90
t3e% f90 -c -O3 -Obl,aggress,split2,unroll2 shallow.f90
t3e% f90 -o master.x master.o shallow.o
In the previous example we used the option -O3. This normally gener-
ates faster programs with reduced turnaround time. The cost of code
optimization is increased compilation time which can sometimes be ex-
cessive. The size of the executable can also increase.
You may also request more information about the optimizations made
by the compiler in the form of a listing file. Compiler options can also
be used to activate debugging or performance tracing (see Chapter 9).
The default size of REAL and INTEGER variables is 8 bytes or 64 bits,
which can be changed to 32 bits with the option -s default32.
Table 5.2 lists the most important CF90 compiler options.
Without explicit compiler options, the compiler assumes conservative
optimization levels, which do not introduce side effects. Some features
can be enabled or disabled with the -e and -d options, see Table 5.3.
5.5 Optimization options
It is very important to note that single-CPU code optimization is essential
in getting good performance on the Cray T3E. If the speed of your code
is only 10 Mflop/s per processor, compared to the peak performance of
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