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README_USC
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--------------------------------------------------------------------
| README (Summary documentation for the Microsecond Clock package) |
| |
| This file briefly describes the functionality and the user |
| interface for the USC system. |
| |
| Written by: Arun Nanda (07/17/91) |
| |
--------------------------------------------------------------------
This directory contains the source files for the Microsecond Clock
package (USC).
The machine classes that are supported are those that have a hardware
clock available with at least 1 microsecond resolution. In that case,
true microsecond resolution is obtained. For other machines (like SUN),
any real-time clock that is available (e.g. gettimeofday) is used and
scaled to a microsecond value. Thus, the clock value returned on such
machines will not yield true microsecond resolution.
CLOCK DATA TYPE
===============
For the purpose of maintaining portability of an application across a
range of architectures, a machine independent data type, denoted by
"usc_time_t", has been defined in the USC package. The current clock
value and the clock rollover point (see below) are returned as data type
usc_time_t. Hence, all variables within an user application used to
store and manipulate microsecond clock values must be declared as type
"usc_time_t".
MICROSECOND CLOCK INTERFACE
===========================
The package comprises of the following macros/functions that are
provided via the include file "usc.h" and the object module "usc.o".
usc_init() : (with no parameters)
This function must be called exactly once
at the beginning before the microsecond
clock can be used.
usc_clock() : (with no parameters)
This function returns the current value of
the microsecond clock as a data item of
type "usc_time_t". The microsecond clock
is a free running counter that rolls over
after the maximum value which is machine
dependent. No assumptions should be made
about what the rollover point for a given
machine is. Instead, the generic macro
usc_rollover_val() should used to determine
this value.
usc_rollover_val(): (with no parameters)
This macro is a generic interface to obtain
the maximum value that the microsecond
clock can take before rolling over to begin
a new cycle. This macro must always be used
to determine the clock rollover point.
An application that uses the USC functional interface must do the
following:
1) Include the file "usc.h" at the beginning of the program.
2) Link the application with the object module "usc.o" and the machine-
specific library mentioned below.
INCLUDE FILE
============
usc.h
OBJECT FILE TO LINK
===================
usc.o
ADDITIONAL MACHINE DEPENDENT LIBRARIES
======================================
The application will also have to be linked with the following machine
dependent libraries in order to enable the microsecond clock to function
properly:
MULTIMAX -lpp
BALANCE -lseq
SYMMETRY -lseq
LIST OF MACHINES SUPPORTED
==========================
ALLIANT
BALANCE
BFLY1
BFLY2
BFLY2_TCMP
DELTA
IBM3090
RS6000
IPSC860_HOST
IPSC860_NODE
MULTIMAX
NEXT
SGI
SUN
SYMMETRY
TITAN