系统GMM问题：stata回归中出现如下警告，不明白什么意思，要怎么解决 Favoring spa

系统GMM问题：stata回归中出现如下警告，不明白什么意思，要怎么解决 Favoring space over speed. To switch, type or click on mata: mata set matafavor speed, perm. Warning: Number of instruments may be large relative to number of observations. Warning: Two-step estimated covariance matrix of moments is singular. Using a generalized inverse to calculate robust weighting matrix for Hansen test. Difference-in-Sargan/Hansen statistics may be negative.