Method, data processing system and computer program for comparing floating point numbers

A data processing system for comparing first and second floating point numbers to generate a result indicative of the comparison unless one or more exception conditions exist, comprising:

• a storage for storing a hierarchy of tests arranged to identify from said first and second floating point numbers whether said one or more exception conditions exist, a first test in said hierarchy predicting whether said one or more exception conditions exist, and each subsequent test in the hierarchy being arranged to determine with more accuracy than a previous test whether said one or more exception conditions exist, each test being arranged to generate a hit signal if that test predicts that said one or more exception conditions exist;
• a processor for executing the first test in said hierarchy and arranged to perform following tasks;
• (a) if the executed test does not generate a hit signal, the processor being arranged to branch to a compare function, and to execute the compare function to generate the result indicative of the comparison of the first and second floating point numbers;
• (b) if the executed test generates a hit signal and is not a final test in the hierarchy, the processor being arranged to branch to a next test in the hierarchy and to execute that next test, and to return to task (a);
• and
• (c) if the executed test generates a hit signal and is the final test in the hierarchy to generate an exception signal indicating a presence of said one or more exception conditions.

A computer program product on a computer readable medium comprising a computer program for configuring a data processing system to perform a method of comparing first and second floating point numbers to generate a result indicative of the comparison unless one or more exception conditions exist, the method comprising the steps of:

• (a) providing a hierarchy of tests arranged to identify from said first and second floating point numbers whether said one or more exception conditions exist, a first test in said hierarchy predicting whether said one or more exception conditions a exist, and each subsequent test in the hierarchy being arranged to determine with more accuracy than a previous test whether said one or more exception conditions exist, each test being arranged to generate a hit signal if that test predicts that said one or more exception conditions exist;
• (b) executing the first test in said hierarchy;
• (c) if the executed test does not generate a hit signal, branching to a compare function, and executing the compare function to generate the result indicative of the comparison of the first and second floating point numbers;
• (d) if the executed test generates a hit signal and is not a final test in the hierarchy, performing the steps of:
• d)(i) branching to a next test in the hierarchy;
• (d)(ii) executing the next test branched to at said step (d)(i);
• and
• (d)(iii)returning to said step (c);
• (e) if the executed test generates a hit signal and is the final test in the hierarchy, generating an exception signal indicating a presence of said one or more exception conditions.