08-18-2011
It's not the ugly triply-nested for-loop that's making it slow, it's the running of multiple external processes per loop. It's wasteful to run awk, grep, sed, and so forth for individual lines -- they are efficient when run on batches of data, but take time to load and quit. Imagine being only allowed to say one word per telephone call... Or in your case, having to say 10,000 words per phone call but only one of them with any meaning.
You're also using externals like expr when your shell (probably) supports better ways of doing math. expr is inefficient for the reason listed above but some shells have nothing better.
How one could do this more efficiently depends on what utilities are available and what system you have. what are they?
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LEARN ABOUT HPUX
serialize
serialize(2) System Calls Manual serialize(2)
NAME
serialize() - force target process to run serially with other processes
SYNOPSIS
DESCRIPTION
The system call is used to force the target process referenced by the pid value passed in to run serially with other processes also marked
for serialization. If the value of pid is zero, then the currently running process is marked for serialization. Once a process has been
marked by the process stays marked until process completion, unless is reissued on the serialized process with timeshare set to 1. If
timeshare is set to 1, the process specified in pid will be returned to normal timeshare scheduling algorithms.
This call is used to improve process throughput since process throughput usually increases for large processes when they are executed seri-
ally instead of allowing each program to run for only a short period of time. By running large processes one at a time, the system makes
more efficient use of the CPU as well as system memory, since each process does not end up constantly faulting in its working set, to only
have the pages stolen when another process starts running. As long as there is enough memory in the system, processes marked by behave no
differently from other processes in the system. However, once memory becomes tight, processes marked by are run one at a time with the
highest priority processes being run first. Each process runs for a finite interval of time before another serialized process is allowed
to run.
RETURN VALUE
returns zero upon successful completion, or nonzero if the system call failed.
ERRORS
If fails, it sets (see errno(2)) to the following value:
The pid passed in does not exist.
WARNINGS
The user has no way of forcing an execution order on serialized processes.
AUTHOR
was developed by HP.
SEE ALSO
serialize(1), privileges(5).
serialize(2)