Add MWE

Author: nsiccha

mwe/Project.toml

@@ -0,0 +1,2 @@
+[deps]
+BridgeStan = "c88b6f0a-829e-4b0b-94b7-f06ab5908f5a"

mwe/mwe.jl

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+using BridgeStan
+
+stan_code = """
+functions {
+  real partial_sum(array[] real slice, int start, int end,
+                   tuple(real, int) params) {
+    real mu = params.1;
+    int K = params.2;
+    real lp = 0;
+    for (i in 1:size(slice)) {
+      lp += normal_lpdf(slice[i] | mu, K);
+    }
+    return lp;
+  }
+}
+data {
+  int N;
+  int K;
+  array[N] real y;
+}
+parameters {
+  real mu;
+}
+model {
+  mu ~ normal(0, 10);
+  target += reduce_sum(partial_sum, y, 1, (mu, K));
+}
+"""
+
+stan_math = ENV["MWE_RUN_DIR"]
+label = ENV["MWE_LABEL"]
+
+workdir = mktempdir()
+stan_file = joinpath(workdir, "mwe.stan")
+write(stan_file, stan_code)
+
+lib = compile_model(stan_file; make_args=["MATH=$stan_math/", "STAN_THREADS=true"])
+
+data = """{"N": 5, "K": 2, "y": [1.0, 2.0, 3.0, 4.0, 5.0]}"""
+sm = StanModel(lib, data)
+
+params = [3.0]  # mu (unconstrained)
+lp = log_density(sm, params)
+lp_grad, grad = log_density_gradient(sm, params)
+
+println("[$label] log_density = $lp")
+println("[$label] gradient = $grad")
+
+@assert isfinite(lp) "log_density should be finite"
+@assert all(isfinite, grad) "gradient should be finite"
+@assert lp ≈ lp_grad "log_density values should match"
+@assert length(grad) == 1 "gradient should have 1 element"
+
+println("[$label] All checks passed!")