ループ計算にPHPのCOSH関数を使用するときにパフォーマンスのボトルネックをトラブルシューティングする方法は？いくつかの最適化の提案は何ですか？

gitbox 2025-06-12

在进行数值计算密集型操作时、即使是诸如cosh（）这样的标准数学函数、也可能成为性能瓶颈的来源。cosh （）是php中计算双曲余弦的内置函数、广泛用于物理模拟、金融建模或其他科学计算中。当它在循环中被频繁调用时、就有可能出现性能下降的问题。

本文将以cosh（）函数为例、分析在php中如何排查性能瓶颈、并给出相应的优化建议。

一、性能瓶颈排查方法

1。

microtime（true）对循环进行包裹、测量函数运行前后时间差。例如：

 <span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-variable">$start</span></span><span> = </span><span><span class="hljs-title function_ invoke__">microtime</span></span><span>(</span><span><span class="hljs-literal">true</span></span><span>);

</span><span><span class="hljs-keyword">for</span></span><span> (</span><span><span class="hljs-variable">$i</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span> < </span><span><span class="hljs-number">1000000</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span>++) {
    </span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">cosh</span></span><span>(</span><span><span class="hljs-variable">$i</span></span><span> * </span><span><span class="hljs-number">0.0001</span></span><span>);
}

</span><span><span class="hljs-variable">$end</span></span><span> = </span><span><span class="hljs-title function_ invoke__">microtime</span></span><span>(</span><span><span class="hljs-literal">true</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"&#25191;&#34892;&#26102;&#38388;: "</span></span><span> . (</span><span><span class="hljs-variable">$end</span></span><span> - </span><span><span class="hljs-variable">$start</span></span><span>) . </span><span><span class="hljs-string">" &#31186;"</span></span><span>;
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>

通过这种方式可以初步判断是否cosh（）函数成为了主要的性能消耗源。

2。

Xdebug

安装完Xdebug后、开启性能分析：

 <span><span><span class="hljs-attr">xdebug.mode</span></span><span>=profile
</span><span><span class="hljs-attr">xdebug.output_dir</span></span><span>=</span><span><span class="hljs-string">"/tmp"</span></span><span>
</span></span>

运行目标脚本后、会生成、 cachegrind文件、然后通过webgrind打开分析、查看cosh（）函数在整个调用栈中所占时间比例。

更多信息可以参考： https：//gitbox.net/docs/php-xdebug-profiler-usage

3。分析内存占用与cpu使用情况

如果你运行的是长时间执行的php 脚本（如 cli 任务）、可以使用トップ、 htop等命令实时查看php

二、优化建议

1 。

如果cosh（）函数的参数是重复的或可以被缓存、可以使用数组缓存其结果、避免重复计算：

 <span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-variable">$cache</span></span><span> = [];
</span><span><span class="hljs-keyword">for</span></span><span> (</span><span><span class="hljs-variable">$i</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span> < </span><span><span class="hljs-number">1000000</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span>++) {
    </span><span><span class="hljs-variable">$arg</span></span><span> = </span><span><span class="hljs-variable">$i</span></span><span> * </span><span><span class="hljs-number">0.0001</span></span><span>;
    </span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-keyword">isset</span></span><span>(</span><span><span class="hljs-variable">$cache</span></span><span>[</span><span><span class="hljs-variable">$arg</span></span><span>])) {
        </span><span><span class="hljs-variable">$cache</span></span><span>[</span><span><span class="hljs-variable">$arg</span></span><span>] = </span><span><span class="hljs-title function_ invoke__">cosh</span></span><span>(</span><span><span class="hljs-variable">$arg</span></span><span>);
    }
    </span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$cache</span></span><span>[</span><span><span class="hljs-variable">$arg</span></span><span>];
}
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>

2。精简精度、换用近似算法

对于一些应用场景、特别是图形渲染或实时性要求较高的系统、可以考虑用双曲余弦的泰勒级数近似实现来替代内置函数。

 <span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">cosh_approx</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$x</span></span></span><span>, </span><span><span class="hljs-variable">$terms</span></span><span> = </span><span><span class="hljs-number">5</span></span><span>) {
    </span><span><span class="hljs-variable">$sum</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>;
    </span><span><span class="hljs-keyword">for</span></span><span> (</span><span><span class="hljs-variable">$n</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-variable">$n</span></span><span> < </span><span><span class="hljs-variable">$terms</span></span><span>; </span><span><span class="hljs-variable">$n</span></span><span>++) {
        </span><span><span class="hljs-variable">$sum</span></span><span> += </span><span><span class="hljs-title function_ invoke__">pow</span></span><span>(</span><span><span class="hljs-variable">$x</span></span><span>, </span><span><span class="hljs-number">2</span></span><span> * </span><span><span class="hljs-variable">$n</span></span><span>) / </span><span><span class="hljs-title function_ invoke__">gmp_intval</span></span><span>(</span><span><span class="hljs-title function_ invoke__">gmp_fact</span></span><span>(</span><span><span class="hljs-number">2</span></span><span> * </span><span><span class="hljs-variable">$n</span></span><span>));
    }
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$sum</span></span><span>;
}
</span></span>

注意这种方式适用于参数范围较小的情形、且结果精度需评估。

3。

在cli环境中、如果要并行处理大量数据、可以使用pcntl_fork（）或者並列扩展进行任务并发、提升整体吞吐量。例如：

 <span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-variable">$processes</span></span><span> = </span><span><span class="hljs-number">4</span></span><span>;
</span><span><span class="hljs-variable">$segment</span></span><span> = </span><span><span class="hljs-number">250000</span></span><span>;

</span><span><span class="hljs-keyword">for</span></span><span> (</span><span><span class="hljs-variable">$i</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span> < </span><span><span class="hljs-variable">$processes</span></span><span>; </span><span><span class="hljs-variable">$i</span></span><span>++) {
    </span><span><span class="hljs-variable">$pid</span></span><span> = </span><span><span class="hljs-title function_ invoke__">pcntl_fork</span></span><span>();
    </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$pid</span></span><span> === </span><span><span class="hljs-number">0</span></span><span>) {
        </span><span><span class="hljs-keyword">for</span></span><span> (</span><span><span class="hljs-variable">$j</span></span><span> = </span><span><span class="hljs-variable">$i</span></span><span> * </span><span><span class="hljs-variable">$segment</span></span><span>; </span><span><span class="hljs-variable">$j</span></span><span> < (</span><span><span class="hljs-variable">$i</span></span><span> + </span><span><span class="hljs-number">1</span></span><span>) * </span><span><span class="hljs-variable">$segment</span></span><span>; </span><span><span class="hljs-variable">$j</span></span><span>++) {
            </span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">cosh</span></span><span>(</span><span><span class="hljs-variable">$j</span></span><span> * </span><span><span class="hljs-number">0.0001</span></span><span>);
        }
        </span><span><span class="hljs-keyword">exit</span></span><span>;
    }
}
</span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-title function_ invoke__">pcntl_waitpid</span></span><span>(</span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-variable">$status</span></span><span>) !== -</span><span><span class="hljs-number">1</span></span><span>);
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>

4。考虑调用更高效的c扩展或通过ffi

对于极限性能需求、可以考虑将部分计算用、c编写为扩展模块、或使用php 7.4+的ffi功能、调用外部的高性能数学库。

https://gitbox.net/articles/php-ffi-performance-math

三、结语

虽然php并非为高性能科学计算设计、但通过合理的优化策略、仍然可以在某些场景下发挥其潜力。在使用如cosh（）这类数学函数进行大规模循环计算时、务必借助性能分析工具找出瓶颈、并采用缓存、并行处理或本地扩展等方式加以优化。这样既能提升运行效率、又能保持代码的可维护性与稳定性。