cpanm Devel::NYTProf

# 运行分析
perl -d:NYTProf myapp.pl

# 生成 HTML 报告
nytprofhtml --open

# 或在浏览器查看
python3 -m http.server 8000 -d nytprof/

use Benchmark qw(timeit timethese cmpthese);

# 计时
my $result = timeit(10000, sub {
    my @sorted = sort { $a <=> $b } (1..100);
});
print "耗时: ", $result->real, " 秒\n";

# 比较多个方案
cmpthese(-5, {
    'sort'    => sub { my @s = sort { $a <=> $b } 1..100 },
    'min_max' => sub { my ($min, $max) = (999, 0); for (1..100) { $min = $_ if $_ < $min; $max = $_ if $_ > $max; } },
});

# 慢：多次 print
for my $i (1..10000) {
    print $fh "$i\n";
}

# 快：一次性写入
my $output = join("\n", 1..10000) . "\n";
print $fh $output;

# 更快：使用数组和 join
my @lines;
for my $i (1..10000) {
    push @lines, "$i\n";
}
print $fh join("", @lines);

# 慢：每次编译正则
for my $line (@lines) {
    if ($line =~ m/\d{4}-\d{2}-\d{2}/) { ... }
}

# 快：预编译正则
my $date_re = qr/\d{4}-\d{2}-\d{2}/;
for my $line (@lines) {
    if ($line =~ $date_re) { ... }
}

# 避免 $&（全局性能惩罚）
# 慢
if ($str =~ /pattern/) { use $& }

# 快
if ($str =~ /pattern/p) { use ${^MATCH} }

# 非贪婪量词在某些场景下更慢
# 可能慢
if ($str =~ m/<.*?>/) { ... }

# 可能快（如果不需要多次匹配）
if ($str =~ m/<[^>]+>/) { ... }

# 慢：数组查找
my @list = (1..10000);
my $found = grep { $_ == 5000 } @list;  # O(n)

# 快：哈希查找
my %hash = map { $_ => 1 } (1..10000);
my $found = exists $hash{5000};          # O(1)

# 慢：传递大数组
sub process { my @data = @_; ... }
process(@huge_array);

# 快：传递引用
sub process { my $data_ref = shift; ... }
process(\@huge_array);

# 慢：创建新哈希
my %copy = %original;

# 快：使用引用
my $ref = \%original;

# 慢：逐行处理
open my $fh, '<', 'bigfile.txt' or die $!;
while (my $line = <$fh>) {
    chomp $line;
    process($line);
}

# 快：一次 slurp（适合小文件）
{
    local $/;
    open my $fh, '<', 'smallfile.txt' or die $!;
    my $content = <$fh>;
    process($content);
}

# 更快：使用 sysread（适合大文件）
open my $fh, '<:raw', 'bigfile.bin' or die $!;
while (sysread($fh, my $buf, 65536)) {
    process($buf);
}

# 慢
for my $i (0..$#array) {
    do_something($array[$i]);
}

# 快：直接遍历
for my $item (@array) {
    do_something($item);
}

# 更快：使用 $_
for (@array) {
    do_something($_);
}

# 慢：创建大量临时列表
my @result = map { transform($_) } grep { filter($_) } @data;

# 快：使用迭代器模式
for my $item (@data) {
    next unless filter($item);
    push @result, transform($item);
}

# 使用 undef 释放内存
my @huge = (1..1_000_000);
# ... 使用 @huge
@huge = ();        # 释放内存
# 或
undef @huge;       # 释放内存

# 大文件处理：逐行读取而非 slurp
# 慢
my @lines = <$fh>;  # 所有行加载到内存

# 快
while (my $line = <$fh>) {
    process($line);   # 逐行处理
}

use Devel::Size qw(total_size);

my @data = (1..1000);
printf "数组内存: %d bytes\n", total_size(\@data);

my %hash = map { $_ => $_ * 2 } (1..1000);
printf "哈希内存: %d bytes\n", total_size(\%hash);

use Inline C;

# 在 Perl 中直接嵌入 C 代码
my $result = fibonacci(30);
print "fibonacci(30) = $result\n";

__END__
__C__

long fibonacci(int n) {
    if (n <= 1) return n;
    return fibonacci(n-1) + fibonacci(n-2);
}

use Benchmark qw(timethese);
use Inline C;

# Perl 版本
sub perl_fib {
    my $n = shift;
    return $n if $n <= 1;
    return perl_fib($n-1) + perl_fib($n-2);
}

# C 版本（在 __C__ 中定义）
timethese(100_000, {
    'perl' => sub { perl_fib(20) },
    'C'    => sub { c_fib(20) },
});

// MyMath.xs
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

MODULE = MyMath   PACKAGE = MyMath

int
add(int a, int b)
    CODE:
        RETVAL = a + b;
    OUTPUT:
        RETVAL

use constant PI => 3.14159265358979;

# 编译时计算
my $area = PI * 5 * 5;   # 常量在编译时替换

# 整数运算（避免浮点开销）
use integer;
my $result = 10 / 3;    # 3（整数除法）

# 小函数可能被编译器内联
sub is_positive { $_[0] > 0 }

# 使用 constant 创建内联常量
use constant MAX_SIZE => 1024;

#!/usr/bin/env perl
use strict;
use warnings;
use Benchmark qw(timeit);

# 方案 1：逐行正则匹配
sub analyze_v1 {
    my ($file) = @_;
    open my $fh, '<', $file or die $!;
    my %counts;
    while (my $line = <$fh>) {
        if ($line =~ /^(\d+\.\d+\.\d+\.\d+)/) {
            $counts{$1}++;
        }
    }
    close $fh;
    return \%counts;
}

# 方案 2：预编译正则
sub analyze_v2 {
    my ($file) = @_;
    open my $fh, '<', $file or die $!;
    my %counts;
    my $ip_re = qr/^(\d+\.\d+\.\d+\.\d+)/;
    while (my $line = <$fh>) {
        if ($line =~ $ip_re) {
            $counts{$1}++;
        }
    }
    close $fh;
    return \%counts;
}

# 方案 3：使用 index 替代正则
sub analyze_v3 {
    my ($file) = @_;
    open my $fh, '<', $file or die $!;
    my %counts;
    while (my $line = <$fh>) {
        my $sp_pos = index($line, ' ');
        next if $sp_pos < 0;
        my $ip = substr($line, 0, $sp_pos);
        $counts{$ip}++;
    }
    close $fh;
    return \%counts;
}

# 对比
# my $t1 = timeit(10, sub { analyze_v1('access.log') });
# my $t2 = timeit(10, sub { analyze_v2('access.log') });
# my $t3 = timeit(10, sub { analyze_v3('access.log') });