奇怪了,我怎么感覺3-3和3-4中間少講了一段代碼?
$arr=[[1,2],[3,4]];
//正常輸出
foreach ($arr as $val)
{
foreach ($val as $key1=>$val1)
{
echo $val1;
}
echo "<br/>";
}
//轉(zhuǎn)置
foreach ($arr as $keyi=>$vali)
{
foreach ($vali as $keyj=>$valj)
{
echo $arr[$keyj][$keyi];
}
echo "<br/>";
}
//正常輸出
foreach ($arr as $val)
{
foreach ($val as $key1=>$val1)
{
echo $val1;
}
echo "<br/>";
}
//轉(zhuǎn)置
foreach ($arr as $keyi=>$vali)
{
foreach ($vali as $keyj=>$valj)
{
echo $arr[$keyj][$keyi];
}
echo "<br/>";
}
2018-01-09
數(shù)據(jù)向量化之后,處理數(shù)據(jù)的效率將會大大提升。numpy包中的dot函數(shù)計算兩個矩陣相乘的時間,要比傳統(tǒng)for循環(huán)遍歷后再相乘的時間要大大減小,大概會減小500倍,感興趣的可以使用Timer的time()函數(shù)計算一下。因此搭建神經(jīng)網(wǎng)絡(luò),所用到的數(shù)據(jù)基本上都是向量化的,這會大大提升開發(fā)的效率。
2017-12-01