Matrix multiplication: Difference between revisions

=={{header|UNIX Shell}}==

<lang bash>

#!/bin/bash

DELAY=0 # increase this if printing of matrices should be slower

echo "This script takes two matrices, henceforth called A and B,

and returns their product, AB.

For the time being, matrices can have integer components only.

"

read -p "Number of rows of matrix A: " arows

read -p "Number of columns of matrix A: " acols

brows="$acols"

echo

echo "Number of rows of matrix B: "$brows

read -p "Number of columns of matrix B: " bcols

crows="$arows"

ccols="$bcols"

echo

echo "Number of rows of matrix AB: " $crows

echo "Number of columns of matrix AB: " $ccols

echo

echo

matrixa=( )

matrixb=( )

# input matrix A

maxlengtha=0

for ((row=1; row<=arows; row++)); do

for ((col=1; col<=acols; col++)); do

checkentry="false"

while [ "$checkentry" != "true" ]; do

read -p "Enter component A[$row, $col]: " number

index=$(((row-1)*acols+col))

matrixa[$index]="$number"

[ "${matrixa[$index]}" -eq "$number" ] && checkentry="true"

echo

done

entry="${matrixa[$index]}"

[ "${#entry}" -gt "$maxlengtha" ] && maxlengtha="${#entry}"

done

echo

done

# print matrix A to guard against errors

if [ "$maxlengtha" -le "5" ]; then

width=8

else

width=$((maxlengtha + 3))

fi

echo "This is matrix A:

"

for ((row=1; row<=arows; row++)); do

for ((col=1; col<=acols; col++)); do

index=$(((row-1)*acols+col))

printf "%${width}d" "${matrixa[$index]}"

sleep "$DELAY"

done

echo; echo # printf %s "\n\n" does not work...

done

echo

echo

# input matrix B

maxlengthb=0

for ((row=1; row<=brows; row++)); do

for ((col=1; col<=bcols; col++)); do

checkentry="false"

while [ "$checkentry" != "true" ]; do

read -p "Enter component B[$row, $col]: " number

index=$(((row-1)*bcols+col))

matrixb[$index]="$number"

[ "${matrixb[$index]}" -eq "$number" ] && checkentry="true"

echo

done

entry="${matrixb[$index]}"

[ "${#entry}" -gt "$maxlengthb" ] && maxlengthb="${#entry}"

done

echo

done

# print matrix B to guard against errors

if [ "$maxlengthb" -le "5" ]; then

width=8

else

width=$((maxlengthb + 3))

fi

echo "This is matrix B:

"

for ((row=1; row<=brows; row++)); do

for ((col=1; col<=bcols; col++)); do

index=$(((row-1)*bcols+col))

printf "%${width}d" "${matrixb[$index]}"

sleep "$DELAY"

done

echo; echo # printf %s "\n\n" does not work...

done

read -p "Hit enter to continue"

# calculate matrix C := AB

maxlengthc=0

time for ((row=1; row<=crows; row++)); do

for ((col=1; col<=ccols; col++)); do

# calculate component C[$row, $col]

runningtotal=0

for ((j=1; j<=acols; j++)); do

rowa="$row"

cola="$j"

indexa=$(((rowa-1)*acols+cola))

rowb="$j"

colb="$col"

indexb=$(((rowb-1)*bcols+colb))

entry_from_A=${matrixa[$indexa]}

entry_from_B=${matrixb[$indexb]}

subtotal=$((entry_from_A * entry_from_B))

((runningtotal+=subtotal))

done

number="$runningtotal"

# store component in the result array

index=$(((row-1)*ccols+col))

matrixc[$index]="$number"

entry="${matrixc[$index]}"

[ "${#entry}" -gt "$maxlengthc" ] && maxlengthc="${#entry}"

done

done

echo

read -p "Hit enter to continue"

echo

# print the matrix C

if [ "$maxlengthc" -le "5" ]; then

width=8

else

width=$((maxlengthc + 3))

fi

echo "The product matrix is:

"

for ((row=1; row<=crows; row++)); do

for ((col=1; col<=ccols; col++)); do

index=$(((row-1)*ccols+col))

printf "%${width}d" "${matrixc[$index]}"

sleep "$DELAY"

done

echo; echo # printf %s "\n\n" does not work...

done

echo

echo

</lang>