code-variants

#!/bin/bash

INFO='
Generate code variants based on formatted comments, e.g.:

x = 0 ### 0 / 1 / 2
y = x + 1 ### x + 1 / x * x

Usage:
    code-variants [ ... options ... ] <source file> [ <prefix> ]

Options:
    --run              Execute generated files in parallel
    --copies <n>       Create identical copies of each variant
    --print            Print generated file names
'

RUN=0
COPIES=
PRINT=

while [ "x${1::2}" = x-- ]; do
    case "x$1" in
        x--run) RUN=1 ;;
        x--copies)
            shift
            COPIES="$(seq $1)" || exit 1
        ;;
        x--print) PRINT=1 ;;
        *)
            echo "$INFO" 1>&2
            exit 1
        ;;
    esac
    shift
done

INPUT_FILE="$1"
PREFIX="${2:-variants/}"

if [ "x$INPUT_FILE" = x ]; then
    echo "$INFO" 1>&2
    exit 1
fi

SOURCES=( "" )
LABELS=( "" )

trim() {
    local v="${1#"${1%%[![:space:]]*}"}"
    v="${v%"${v##*[![:space:]]}"}"
    echo -n "$v"
}

add_branch() {
    IFS='/' read -r -a options <<< "$2"
    if [ "${#options[@]}" -lt 2 ]; then
        echo "Error: invalid format: '$2'" 1>&2
        exit 1
    fi
    REPLACE=
    for option in "${options[@]}"; do
        option=$(trim "$option")
        if [ "x${1/$option}" != "x$1" ]; then
            if [ ${#option} -gt ${#REPLACE} ]; then
                REPLACE="$option"
            fi
        fi
    done
    if [ "x$REPLACE" = x ]; then
        echo "Error: variants not found in line: '$2'" 1>&2
        exit 1
    fi
    NEW_SOURCES=()
    for source in "${SOURCES[@]}"; do
        for option in "${options[@]}"; do
            option=$(trim "$option")
            NEW_SOURCES+=( "$source${1/$REPLACE/$option}"$'\n' )
        done
    done
    SOURCES=( "${NEW_SOURCES[@]}" )
    NEW_LABELS=()
    for label in "${LABELS[@]}"; do
        for option in "${options[@]}"; do
            option="${option,,}"
            NEW_LABELS+=( "${label}_$(echo ${option//[^a-z0-9_.-]/})" )
        done
    done
    LABELS=( "${NEW_LABELS[@]/#_/}" )
}

while IFS='' read -r line; do
    COMMENT="${line##*###}"
    if [ "x$COMMENT" != "x$line" ]; then
        if add_branch "${line%###*}" "$COMMENT"; then
            continue
        fi
    fi
    line="$line"$'\n'
    SOURCES=( "${SOURCES[@]/%/$line}" )
done < "$INPUT_FILE"

if [ "x$COPIES" != x ]; then
    NEW_SOURCES=()
    for source in "${SOURCES[@]}"; do
        for copy in $COPIES; do
            NEW_SOURCES+=( "$source" )
        done
    done
    SOURCES=( "${NEW_SOURCES[@]}" )
    NEW_LABELS=()
    for label in "${LABELS[@]}"; do
        for copy in $COPIES; do
            NEW_LABELS+=( "${label}_copy$copy" )
        done
    done
    LABELS=( "${NEW_LABELS[@]/#_/}" )
fi

if [ "${#SOURCES[@]}" -lt 2 ]; then
    echo "Error: no variants found in '$INPUT_FILE'" 1>&2
    exit 1
fi

if [ "x$PRINT" != x ]; then
    for label in "${LABELS[@]}"; do
        echo "$label"
    done
fi

if [ "x$RUN" != x1 ]; then
    for id in "${!SOURCES[@]}"; do
        OUTPUT_FILE="$PREFIX${LABELS[$id]}"
        mkdir -p "$(dirname "$OUTPUT_FILE")" || exit 1
        echo "${SOURCES[$id]}" > "$OUTPUT_FILE" || exit 1
        chmod "$OUTPUT_FILE" --reference="$INPUT_FILE" || true
    done
    exit 0
fi

TMPDIR=$(mktemp -d) || exit 1
trap "rm -rf $TMPDIR" EXIT

for id in "${!SOURCES[@]}"; do
    OUTPUT_FILE="$TMPDIR/${LABELS[$id]}.run"
    echo "${SOURCES[$id]}" > "$OUTPUT_FILE" || exit 1
    chmod +x "$OUTPUT_FILE"
done

echo '
all: $(patsubst %,'"$PREFIX"'%.out, '"${LABELS[@]}"')

'"$PREFIX"'%.out:
'$'\t''@echo Running variant: $*...
'$'\t''@'"$TMPDIR"'/$*.run > '"$TMPDIR"'/$*.out
'$'\t''@mkdir -p $(dir $@)
'$'\t''@cp '"$TMPDIR"'/$*.out $@
' > "$TMPDIR/makefile"

NUM_THREADS=$(grep -c ^processor /proc/cpuinfo) || exit 1
echo "Max threads: $NUM_THREADS" 1>&2
make -f "$TMPDIR/makefile" -j "$NUM_THREADS" 1>&2 || exit 1