de>(int y | matrix x, real alpha, vector beta)</code><br>The log Poisson probability mass of <code>y</code> given the log-rate <code>alpha + x * beta</code>, where the same intercept <code>alpha</code> and dependent variable value <code>y</code> are used for all observations. The number of columns of <code>x</code> needs to match the size of the coefficient vector <code>beta</code>. If <code>x</code> and <code>y</code> are data (not parameters) this function can be executed on a GPU.</p>
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