9.1.4.1 Removing I/O From Key Loops

I/O within a loop or loop nest enclosing the significant computational work of a program will seriously degrade performance. The amount of CPU time spent in the I/O library might be a major portion of the time spent in the loop. (I/O also causes process interrupts, thereby degrading program throughput.) By moving I/O out of the computation loop wherever possible, the number of calls to the I/O library can be greatly reduced.