fix test proposal

Author: francoisbonneau

include/geode/stochastic/sampling/mcmc/proposal/classical_proposals.hpp

@@ -32,9 +32,7 @@ namespace geode
 {
     template < typename Geometry >
     std::unique_ptr< ProposalKernel< Geometry > > create_birth_death_kernel(
-        const MarkedObjectSampler< Geometry >& sampler,
-        double birth_prob = 0.5,
-        double death_prob = 0.5 )
+        const MarkedObjectSampler< Geometry >& sampler, double birth_prob )
     {
         auto kernel = std::make_unique< ProposalKernel< Geometry > >();
         kernel->add_move( std::make_unique< BirthDeathMove< Geometry > >(
@@ -46,16 +44,17 @@ namespace geode
     std::unique_ptr< ProposalKernel< Geometry > >
         create_birth_death_change_kernel(
             const MarkedObjectSampler< Geometry >& sampler,
-            double birth_prob = 0.33,
-            double death_prob = 0.33,
-            double change_prob = 0.34 )
+            double birth_prob,
+            double death_prob )
     {
-        auto kernel = std::make_unique< ProposalKernel< Geometry > >();
         auto birth_death_prob = birth_prob + death_prob;
+        OPENGEODE_EXCEPTION( birth_death_prob < 1.,
+            "[Proposal Kernel] - changes should be allowed." );
+        auto kernel = std::make_unique< ProposalKernel< Geometry > >();
         kernel->add_move( std::make_unique< BirthDeathMove< Geometry > >(
             sampler, birth_death_prob, birth_prob / birth_death_prob ) );
         kernel->add_move( std::make_unique< ChangeMove< Geometry > >(
-            sampler, change_prob ) );
+            sampler, 1. - birth_death_prob ) );
         return kernel;
     }
 } // namespace geode

tests/stochastic/sampling/mcmc/proposal/test-proposal-kernel.cpp

@@ -62,7 +62,7 @@ namespace
 
         // Create classical birth-death-change kernel
         auto kernel = geode::create_birth_death_change_kernel< geode::Point2D >(
-            sampler, 0.5 );
+            sampler, 0.4, 0.4 );
 
         geode::RandomEngine engine;
 
@@ -85,9 +85,11 @@ namespace
                     OPENGEODE_EXCEPTION( prop.log_forward_prob <= 0.0,
                         "[test proposal] Birth forward log-prob must be <= "
                         "0." );
+
                     OPENGEODE_EXCEPTION(
                         std::abs( prop.log_backward_prob
-                                  - ( -std::log( config.size() + 1.0 ) ) )
+                                  - ( std::log( 0.8 * 0.5 )
+                                      - std::log( config.size() + 1.0 ) ) )
                             < geode::GLOBAL_EPSILON,
                         "[test proposal] Birth backward log-prob mismatch." );
                     break;

tests/stochastic/sampling/mcmc/test-metropolis-hasting-sampler.cpp

@@ -177,7 +177,7 @@ int main()
 
         // Create classical birth-death-change kernel
         auto kernel = geode::create_birth_death_change_kernel< geode::Point2D >(
-            sampler, 0.1, 0.1, 0.8 );
+            sampler, 0.1, 0.1 );
 
         geode::GibbsEnergy< geode::Point2D > poisson_energy;