Increase atol on specific tests for x86 (#2449)

Author: penelopeysm

test/mcmc/ess.jl

@@ -71,7 +71,11 @@ using Turing
                 @varname(mu2) => ESS(),
             )
             chain = sample(StableRNG(seed), MoGtest_default, alg, 2000)
-            check_MoGtest_default(chain; atol=0.1)
+            # (penelopeysm) Note that the tolerance for x86 needs to be larger
+            # because CSMC (i.e. PG) is not reproducible across architectures.
+            # See https://github.com/TuringLang/Turing.jl/issues/2446.
+            atol = Sys.ARCH == :i686 ? 0.12 : 0.1
+            check_MoGtest_default(chain; atol=atol)
         end
 
         @testset "TestModels" begin

test/mcmc/gibbs.jl

@@ -481,7 +481,13 @@ end
         # the posterior is analytically known? Doing 10_000 samples to run the test suite
         # is not ideal
         # Issue ref: https://github.com/TuringLang/Turing.jl/issues/2402
-        @test isapprox(mean(num_ms), 8.6087; atol=0.8)
+
+        # (penelopeysm) Note also the larger atol on x86 runners. This is
+        # needed because PG is not fully reproducible across architectures,
+        # even when seeded as above. See
+        # https://github.com/TuringLang/Turing.jl/issues/2446
+        mean_atol = Sys.ARCH == :i686 ? 1.3 : 0.8
+        @test isapprox(mean(num_ms), 8.6087; atol=mean_atol)
         @test isapprox(std(num_ms), 1.8865; atol=0.02)
     end