diff --git a/src/modules/cm-precompute.ts b/src/modules/cm-precompute.ts
index 3ee35c829..a0e55602b 100644
--- a/src/modules/cm-precompute.ts
+++ b/src/modules/cm-precompute.ts
@@ -205,7 +205,7 @@ const listCandidateCount = (ncList: NameCount.List): number => {
 };
 
 export const preCompute = (first: number, last: number, args: any): boolean => {
-    const maxSum = last;
+    const maxSum = args.load_max;
     const merge_only = args.merge_only || false;
 
     const begin = new Date();
diff --git a/src/native-modules/experiment/filter-stream.cpp b/src/native-modules/experiment/filter-stream.cpp
index 3343a2c54..62264630f 100644
--- a/src/native-modules/experiment/filter-stream.cpp
+++ b/src/native-modules/experiment/filter-stream.cpp
@@ -14,7 +14,7 @@ extern __constant__ FilterStreamData::Device stream_data_[kMaxStreams];
 void FilterStreamData::Device::init(FilterStream& stream, FilterData& mfd) {
   if (!stream.host.device_initialized) {
     assert(stream.host.stream_idx() < kMaxStreams);
-    alloc_buffers(mfd, stream.cuda_stream);
+    alloc_buffers(mfd, stream.stride, stream.cuda_stream);
     copy_to_symbol(stream.host.stream_idx(), stream.cuda_stream);
     stream.host.device_initialized = true;
   }
@@ -32,10 +32,10 @@ void FilterStreamData::Device::alloc_copy_source_index_list(const Host& host,
     }
     cuda_malloc_async((void**)&src_idx_list, num_bytes, stream,
         "device.src_idx_list");
-    num_src_idx = num_host_src_idx;
-    // device members updated; need to (re)copy to symbol
-    copy_to_symbol(host.stream_idx(), stream);
   }
+  num_src_idx = num_host_src_idx;
+  // num_src_idx may shrink between sums, so always refresh constant memory.
+  copy_to_symbol(host.stream_idx(), stream);
   // copy source indices
   auto err = cudaMemcpyAsync(src_idx_list, host.src_idx_list.data(), num_bytes,
       cudaMemcpyHostToDevice, stream);
@@ -43,8 +43,9 @@ void FilterStreamData::Device::alloc_copy_source_index_list(const Host& host,
 }
 
 void FilterStreamData::Device::alloc_buffers(FilterData& mfd,
-    cudaStream_t stream) {
-  const auto [grid_size, _] = get_filter_kernel_grid_block_sizes();
+    size_t max_active_sources, cudaStream_t stream) {
+  const auto [grid_size, _] =
+      get_filter_kernel_grid_block_sizes(max_active_sources);
   if (mfd.device_xor.num_unique_variations) {
     const auto num_bytes = mfd.device_xor.num_unique_variations * grid_size
         * sizeof(index_t);
diff --git a/src/native-modules/experiment/filter-stream.h b/src/native-modules/experiment/filter-stream.h
index 47713d31e..74b94c668 100644
--- a/src/native-modules/experiment/filter-stream.h
+++ b/src/native-modules/experiment/filter-stream.h
@@ -27,6 +27,13 @@ struct FilterStreamData {
   struct Device {
     void init() {
       src_idx_list = nullptr;
+      xor_src_compat_uv_indices = nullptr;
+      or_xor_compat_uv_indices = nullptr;
+#ifdef VARIATIONS_RESULTS
+      variations_compat_results = nullptr;
+      num_variations_results_per_block = 0;
+#endif
+      or_src_bits_compat_results = nullptr;
       num_src_idx = 0;
     }
     void init(FilterStream& stream, FilterData& mfd);
@@ -61,7 +68,8 @@ struct FilterStreamData {
     index_t num_src_idx;
 
   private:
-    void alloc_buffers(FilterData& fd, cudaStream_t stream);
+    void alloc_buffers(FilterData& fd, size_t max_active_sources,
+        cudaStream_t stream);
     void copy_to_symbol(index_t idx, cudaStream_t stream);
   };  // struct Device
 };  // struct FilterStreamData
diff --git a/src/native-modules/experiment/filter-support.cpp b/src/native-modules/experiment/filter-support.cpp
index dc1032e45..4c09176df 100644
--- a/src/native-modules/experiment/filter-support.cpp
+++ b/src/native-modules/experiment/filter-support.cpp
@@ -500,8 +500,6 @@ filter_sources(FilterSwarm& swarm, const FilterParams& params,
 
   // TODO: FilterStreamData::Host, resize_results()
   std::vector<result_t> results(num_results);
-  // TODO: this is dumb
-  swarm.init(stride);
   auto t = util::Timer::start_timer();
   const auto [num_processed, num_compat] =  //
       run_concurrent_filter_kernels(params.sum, swarm, params.threads_per_block,
@@ -655,6 +653,8 @@ filter_task_result_t filter_task(FilterData& mfd, FilterParams params) {
   auto& swarm = swarm_pool_.acquire();
   const auto num_streams = params.num_streams ? params.num_streams : 1;
   swarm.ensure_streams(num_streams); // set_num_streams might be better
+  const auto stride = params.stride ? params.stride : int(idx_lists.size());
+  swarm.init(stride);
 
   const auto& stream = swarm.at(0);
   stream.copy_start.record(stream.cuda_stream);
diff --git a/src/native-modules/experiment/filter.cu b/src/native-modules/experiment/filter.cu
index 2bb39f6ab..d28e55d89 100644
--- a/src/native-modules/experiment/filter.cu
+++ b/src/native-modules/experiment/filter.cu
@@ -778,13 +778,15 @@ __global__ void filter_kernel(result_t* RESTRICT results, index_t swarm_idx,
 
 }  // anonymous namespace
 
-std::pair<int, int> get_filter_kernel_grid_block_sizes() {
+std::pair<int, int> get_filter_kernel_grid_block_sizes(size_t num_sources) {
   // hard-code 64 due to cub::BlockScan
   const auto block_size = 64;  // threads_per_block ? threads_per_block : 64;
   const auto max_threads_per_sm = CudaDevice::get().max_threads_per_sm();
   const auto blocks_per_sm = max_threads_per_sm / block_size;
   assert(blocks_per_sm * block_size == max_threads_per_sm);
-  const auto grid_size = CudaDevice::get().num_sm() * blocks_per_sm;
+  const auto max_grid_size = CudaDevice::get().num_sm() * blocks_per_sm;
+  assert(num_sources > 0);
+  const auto grid_size = std::min<int>(max_grid_size, int(num_sources));
   return std::make_pair(grid_size, block_size);
 }
 
@@ -805,7 +807,8 @@ void run_filter_kernel(int /*threads_per_block*/, index_t swarm_idx,
     FilterStream& stream, result_t* device_results) {
   stream.is_running = true;
   stream.increment_sequence_num();
-  const auto [grid_size, block_size] = get_filter_kernel_grid_block_sizes();
+  const auto [grid_size, block_size] =
+      get_filter_kernel_grid_block_sizes(stream.host.src_idx_list.size());
   // xor_results could probably be moved to global
   const auto shared_bytes = kSharedIndexCount
           * sizeof(shared_index_t)            // indices
diff --git a/src/native-modules/experiment/filter.cuh b/src/native-modules/experiment/filter.cuh
index e7f191bd1..31c73c5bf 100644
--- a/src/native-modules/experiment/filter.cuh
+++ b/src/native-modules/experiment/filter.cuh
@@ -20,7 +20,7 @@ void run_get_compatible_sources_kernel(
     size_t num_src_desc_pairs, result_t* device_resultsy,
     cudaStream_t sync_stream, cudaStream_t stream);
 
-std::pair<int, int> get_filter_kernel_grid_block_sizes();
+std::pair<int, int> get_filter_kernel_grid_block_sizes(size_t num_sources);
 
 void copy_filter_data_to_symbols(const FilterData& mfd, cudaStream_t stream);
 
@@ -42,4 +42,3 @@ inline constexpr void dump_compat_src_indices(
 #endif
 
 }  // namespace cm
-