From the Preface:
The C programs for several algorithms that are discussed in this book. All these codes were developed and tested using the widely available Gnu GCC compiler. Note that these codes are not optimally tuned, indeed, fine tuning C code is usually specific to a single compiler version and often hurt the code’s legibility. Where timings are given, they were measured on an Intel Core 2 Duo at 2.4 Ghz