GAT Documentation

Now, as the turbid, conceptual backwaters of the resource management package are, hopefully, a little less murky, we can move on to the process of putting all these abstractions into practice. We will begin this process by examining the creation and destruction of a GATHardwareResourceDescription.

The class GATHardwareResourceDescription can most simply be conceptualized as a container for a GATTable, a class covered in Appendix

. So, it's a small wonder that to create a GATHardware Description instance one uses a function of the following form

The first argument to this function is a GATTable instance. This GATTable instance, the contents of which we will cover below, contains the description of the hardware resource we are trying to represent. This function returns a GATHardwareResourceDescription or NULL upon the occurrence of an error.

A hardware resource, at least as far as GAT is concerned, can be described by a set of name/value pairs. For example, one could specify that a hardware resource has a PowerPC CPU through the following name/value pair

One similarly could specify that a hardware resource be a Power Macintosh by using the next name/value pair

To construct a GATHardwareResourceDescription, as we saw above, one requires a GATTable instance. It is this GATTable instance which contains the various name/value pairs describing the resultant GATHardwareResourceDescription.

So, you may ask, can I place any name/value pairs in such a GATTable. Well, the answer is yes; however, GAT is only required to support a certain set of name value pairs. The extra name/value pairs may be ignored by GAT. The full set of supported name/value pairs, along with each value's type, can be found in table

Name	Type	Description
`memory.size`	`Float`	The minimum memory in GB.
`memory.accesstime`	`Float`	The minimum memory access time in ns.
`memory.str`	`Float`	The minimum sustained transfer rate in GB/s.
`machine.type`	`String`	The machine type as returned from `uname -m`.
`machine.node`	`String`	The machine node name as returned from `uname -n`.
`cpu.type`	`String`	The generic cpu type as returned from `uname -p`.
`cpu.speed`	`Float`	The minimum cpu speed in GHz.
`disk.size`	`Float`	The minimum size of the hard drive in GB.
`disk.accesstime`	`Float`	The minimum disk access time in ms.
`disk.str`	`Float`	The minimum sustained transfer rate in MB/s.

If a particular name/value pair is not specified in a particular GATTable instance, then GAT assumes that this name/value pair can take on any value. So, for example, if the there is no key disk.accesstime in a GATTable instance, then GAT assumes that this property can take on any value. In addition, if one specifies a particular name/value pair, say memory.size=1024, GAT will make the obvious assumption that this specification would describe a hardware resource with

or more GB of memory.

To destroy the so created GATHardwareResourceDescription one uses the following function

This function takes as its first argument a pointer to a GATHardwareResourceDescription. This points to the GATHardwareResourceDescription to be destroyed. Upon successful completion this any resources this GATHardwareResourceDescription maintained will be released.

Constructing and Destroying HardwareDescription Instances