// 找到最大的列主元
for(j = i; j < size; j++)
{
if(p[j][i] > largest)
{
largest = p[j][i];
swap_index = j;
}
}
//如果最大列主元不在子块的第一行，那么进行交换
if(i != swap_index)
{
double temp = 0;
for(j = 0; j < size; j++)
{
temp = p[i][j];
p[i][j] = p[swap_index][j];
p[swap_index][j] = temp;
}
temp = B[i];
B[i] = B[swap_index];
B[swap_index] = temp;
}
//进行消元
double mi = 1.0;
for(j = i + 1; j < size; j++)
{
mi = p[j][i]/p[i][i];
for(int k = i; k < size; k++)
{
p[j][k] = p[j][k] - mi * p[i][k];
}
B[j] = B[j] - mi * B[i];
}
}