Comment dépanner les goulots d'étranglement des performances lors de l'utilisation de la fonction COSH de PHP pour le calcul de la boucle? Quelles sont les suggestions d'optimisation?

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. 使用 MicroTime () 精准测量耗时

最基础的方式是使用Microme (vrai)对循环进行包裹，：:

 <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. 使用 xdebug + webgrind 可视化分析

Xdebug 是 php 的强大调试和性能分析工具，通过它配合 webgrind 或 qcachegrind ，可以详细分析函数调用的耗时。

安装完 xdebug 后，：：

 <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TOP 、 HTOP等命令实时查看 PHP 进程的 CPU 和内存使用状况。也可以在脚本中使用Memory_get_usage ()进行内存快照记录。

二、优化建议

1. 减少不必要的Cosh ()调用

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，：:

 <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. 使用多进程或多线程处理

在 CLI 环境中，如果要并行处理大量数据，可以使用PCNTL_FORK ()或者Parallèle扩展进行任务并发，：：

 <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>