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Full Discussion: any way to speed up calculations in bash script
Top Forums Shell Programming and Scripting any way to speed up calculations in bash script Post 302276886 by cfajohnson on Thursday 15th of January 2009 12:08:39 AM
Old 01-15-2009
Quote:
Originally Posted by npatwardhan
is there any way i can speed it up?

Don't call the external command 21,000 times. Pipe your calculations to a single instance of it.

And I would use awk rather than bc.

Code:
while [ $j -lt $outer ];do
  i=0
  while [ $i -lt $count1 ];do
    printf "%f\n" "${ARRAY1[k]} - ${ARRAY2[j]}"
    i=$(( $i + 1 ))
    k=$(( $k + 1 ))
  done 
  echo
  j=$(( $j + 1 ))
done | awk '/^$/ { print; next }
{ printf "%.1f," $1 - $2 }
'  > "$count.diff"

If you are processing the entire arrays:

Code:
for a in "${ARRAY1[@]}"
do
  printf "%f $a\n" ${ARRAY2[@]}
  echo
done | awk '/^$/ { print; next }
{ printf "%.1f,", $1 - $2 }
'

 

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LEARN ABOUT OSX

echo

ECHO(1) 						    BSD General Commands Manual 						   ECHO(1)

NAME

     echo -- write arguments to the standard output

SYNOPSIS

     echo [-n] [string ...]

DESCRIPTION

     The echo utility writes any specified operands, separated by single blank (' ') characters and followed by a newline ('
') character, to the
     standard output.

     The following option is available:

     -n    Do not print the trailing newline character.  This may also be achieved by appending 'c' to the end of the string, as is done by iBCS2
	   compatible systems.	Note that this option as well as the effect of 'c' are implementation-defined in IEEE Std 1003.1-2001
	   (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for maximum portability are strongly encouraged to use printf(1) to sup-
	   press the newline character.

     Some shells may provide a builtin echo command which is similar or identical to this utility.  Most notably, the builtin echo in sh(1) does
     not accept the -n option.	Consult the builtin(1) manual page.

EXIT STATUS

     The echo utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

     builtin(1), csh(1), printf(1), sh(1)

STANDARDS

     The echo utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'') as amended by Cor. 1-2002.

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								  April 12, 2003							       BSD
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