feat: comptime configurable thread count

We can set threadcount with -Dthread-count=<NUMBER>, or leave it up to
the default of @max(std.Thread.getCpuCount() - 1, 1).

Author: spiral-ladder

bindings/napi/root.zig

@@ -3,6 +3,7 @@ const napi = @import("zapi:zapi");
 const pool = @import("./pool.zig");
 const pubkeys = @import("./pubkeys.zig");
 const config = @import("./config.zig");
+const options = @import("bls_options");
 const shuffle = @import("./shuffle.zig");
 const metrics = @import("./metrics.zig");
 const BeaconStateView = @import("./BeaconStateView.zig");
@@ -36,7 +37,13 @@ var env_cleanup: EnvCleanup = .{};
 fn register(env: napi.Env, exports: napi.Value) !void {
     if (env_refcount.fetchAdd(1, .monotonic) == 0) {
         // First environment — initialize shared state.
-        const cpu_count = std.Thread.getCpuCount() catch 1;
+        // in your threadpool init
+        var cpu_count: usize = options.thread_count;
+        if (options.thread_count == 0) {
+            std.debug.print("Note: no -Dthread-count set, will use runtime CPU count minus 1: {}\n", .{cpu_count});
+            cpu_count = @max((try std.Thread.getCpuCount()) - 1, 1);
+        }
+
         const n_workers = @min(cpu_count, @import("bls").ThreadPool.MAX_WORKERS);
         try blst.initThreadPool(@intCast(n_workers));
         try pool.state.init();

build.zig

@@ -13,6 +13,11 @@ pub fn build(b: *std.Build) void {
     options_build_options.addOption([]const u8, "preset", option_preset);
     const options_module_build_options = options_build_options.createModule();
 
+    const options_bls_options = b.addOptions();
+    const option_thread_count = b.option(u8, "thread_count", "") orelse 0;
+    options_bls_options.addOption(u8, "thread_count", option_thread_count);
+    const options_module_bls_options = options_bls_options.createModule();
+
     const options_download_era_options = b.addOptions();
     const option_era_base_url = b.option([]const u8, "era_base_url", "") orelse "https://mainnet.era.nimbus.team";
     options_download_era_options.addOption([]const u8, "era_base_url", option_era_base_url);
@@ -1153,6 +1158,7 @@ pub fn build(b: *std.Build) void {
     module_bench_process_epoch.addImport("era", module_era);
 
     module_bindings.addImport("bls", module_bls);
+    module_bindings.addImport("bls_options", options_module_bls_options);
     module_bindings.addImport("persistent_merkle_tree", module_persistent_merkle_tree);
     module_bindings.addImport("ssz", module_ssz);
     module_bindings.addImport("consensus_types", module_consensus_types);

zbuild.zon

@@ -44,6 +44,12 @@
                 .type = "string",
             },
         },
+        .bls_options = .{
+            .thread_count = .{
+                .default = 0,
+                .type = "u8",
+            },
+        },
         .download_era_options = .{
             .era_base_url = .{
                 .default = "https://mainnet.era.nimbus.team",
@@ -245,6 +251,7 @@
                 .root_source_file = "bindings/napi/root.zig",
                 .imports = .{
                     .bls,
+                    .bls_options,
                     .persistent_merkle_tree,
                     .ssz,
                     .consensus_types,