fix: don't use pinned memory in cpu_backend (PROOF-921) (#196)

don't use pinned memory in cpu_backend

cbindings/fixed_pedersen.t.cc

@@ -95,6 +95,29 @@ TEST_CASE("we can compute multi-exponentiations with a fixed set of generators")
     sxt_multiexp_handle_free(hp);
   }
 
+  SECTION("we can read and write a handle to a file with cpu backend") {
+    cbn::reset_backend_for_testing();
+    const sxt_config config = {SXT_CPU_BACKEND, 0};
+
+    REQUIRE(sxt_init(&config) == 0);
+    bastst::temp_file temp_file{std::ios::binary};
+    temp_file.stream().close();
+
+    wrapped_handle h{generators.data(), 2};
+    REQUIRE(h.h != nullptr);
+
+    sxt_multiexp_handle_write_to_file(h.h, temp_file.name().c_str());
+
+    auto hp = sxt_multiexp_handle_new_from_file(SXT_CURVE_RISTRETTO255, temp_file.name().c_str());
+
+    uint8_t scalars[] = {1, 0, 0, 2};
+    c21t::element_p3 res;
+    sxt_fixed_multiexponentiation(&res, hp, 2, 1, 2, scalars);
+    REQUIRE(res == generators[0] + 2 * 256 * generators[1]);
+
+    sxt_multiexp_handle_free(hp);
+  }
+
   SECTION("we can compute a multiexponentiation in packed form") {
     cbn::reset_backend_for_testing();
     const sxt_config config = {SXT_GPU_BACKEND, 0};

sxt/cbindings/backend/computational_backend.cc

@@ -21,20 +21,6 @@
 #include "sxt/multiexp/pippenger2/in_memory_partition_table_accessor.h"
 
 namespace sxt::cbnbck {
-//--------------------------------------------------------------------------------------------------
-// read_partition_table_accessor
-//--------------------------------------------------------------------------------------------------
-std::unique_ptr<mtxpp2::partition_table_accessor_base>
-computational_backend::read_partition_table_accessor(cbnb::curve_id_t curve_id,
-                                                     const char* filename) const noexcept {
-  std::unique_ptr<mtxpp2::partition_table_accessor_base> res;
-  cbnb::switch_curve_type(
-      curve_id, [&]<class U, class T>(std::type_identity<U>, std::type_identity<T>) noexcept {
-        res = std::make_unique<mtxpp2::in_memory_partition_table_accessor<U>>(filename);
-      });
-  return res;
-}
-
 //--------------------------------------------------------------------------------------------------
 // write_partition_table_accessor
 //--------------------------------------------------------------------------------------------------

sxt/cbindings/backend/computational_backend.h

@@ -124,8 +124,8 @@ class computational_backend {
                                          const unsigned* output_lengths, unsigned num_outputs,
                                          const uint8_t* scalars) const noexcept = 0;
 
-  std::unique_ptr<mtxpp2::partition_table_accessor_base>
-  read_partition_table_accessor(cbnb::curve_id_t curve_id, const char* filename) const noexcept;
+  virtual std::unique_ptr<mtxpp2::partition_table_accessor_base>
+  read_partition_table_accessor(cbnb::curve_id_t curve_id, const char* filename) const noexcept = 0;
 
   void write_partition_table_accessor(cbnb::curve_id_t curve_id,
                                       const mtxpp2::partition_table_accessor_base& accessor,

sxt/cbindings/backend/cpu_backend.cc

@@ -213,6 +213,21 @@ void cpu_backend::fixed_multiexponentiation(void* res, cbnb::curve_id_t curve_id
   });
 }
 
+//--------------------------------------------------------------------------------------------------
+// read_partition_table_accessor
+//--------------------------------------------------------------------------------------------------
+std::unique_ptr<mtxpp2::partition_table_accessor_base>
+cpu_backend::read_partition_table_accessor(cbnb::curve_id_t curve_id,
+                                           const char* filename) const noexcept {
+  std::unique_ptr<mtxpp2::partition_table_accessor_base> res;
+  cbnb::switch_curve_type(curve_id, [&]<class U, class T>(std::type_identity<U>,
+                                                          std::type_identity<T>) noexcept {
+    res =
+        std::make_unique<mtxpp2::in_memory_partition_table_accessor<U>>(filename, basm::alloc_t{});
+  });
+  return res;
+}
+
 //--------------------------------------------------------------------------------------------------
 // get_cpu_backend
 //--------------------------------------------------------------------------------------------------

sxt/cbindings/backend/cpu_backend.h

@@ -78,6 +78,10 @@ class cpu_backend final : public computational_backend {
                                  const unsigned* output_bit_table, const unsigned* output_lengths,
                                  unsigned num_outputs,
                                  const uint8_t* scalars) const noexcept override;
+
+  std::unique_ptr<mtxpp2::partition_table_accessor_base>
+  read_partition_table_accessor(cbnb::curve_id_t curve_id,
+                                const char* filename) const noexcept override;
 };
 
 //--------------------------------------------------------------------------------------------------

sxt/cbindings/backend/gpu_backend.cc

@@ -255,6 +255,20 @@ void gpu_backend::fixed_multiexponentiation(void* res, cbnb::curve_id_t curve_id
       });
 }
 
+//--------------------------------------------------------------------------------------------------
+// read_partition_table_accessor
+//--------------------------------------------------------------------------------------------------
+std::unique_ptr<mtxpp2::partition_table_accessor_base>
+gpu_backend::read_partition_table_accessor(cbnb::curve_id_t curve_id,
+                                           const char* filename) const noexcept {
+  std::unique_ptr<mtxpp2::partition_table_accessor_base> res;
+  cbnb::switch_curve_type(
+      curve_id, [&]<class U, class T>(std::type_identity<U>, std::type_identity<T>) noexcept {
+        res = std::make_unique<mtxpp2::in_memory_partition_table_accessor<U>>(filename);
+      });
+  return res;
+}
+
 //--------------------------------------------------------------------------------------------------
 // get_gpu_backend
 //--------------------------------------------------------------------------------------------------

sxt/cbindings/backend/gpu_backend.h

@@ -80,6 +80,10 @@ class gpu_backend final : public computational_backend {
                                  const unsigned* output_bit_table, const unsigned* output_lengths,
                                  unsigned num_outputs,
                                  const uint8_t* scalars) const noexcept override;
+
+  std::unique_ptr<mtxpp2::partition_table_accessor_base>
+  read_partition_table_accessor(cbnb::curve_id_t curve_id,
+                                const char* filename) const noexcept override;
 };
 
 //--------------------------------------------------------------------------------------------------

sxt/multiexp/pippenger2/BUILD

@@ -153,6 +153,7 @@ sxt_cc_component(
         "//sxt/base/device:memory_utility",
         "//sxt/base/error:assert",
         "//sxt/base/error:panic",
+        "//sxt/base/memory:alloc",
         "//sxt/memory/management:managed_array",
         "//sxt/memory/resource:pinned_resource",
     ],

sxt/multiexp/pippenger2/in_memory_partition_table_accessor.h

@@ -25,6 +25,7 @@
 #include "sxt/base/device/memory_utility.h"
 #include "sxt/base/error/assert.h"
 #include "sxt/base/error/panic.h"
+#include "sxt/base/memory/alloc.h"
 #include "sxt/memory/management/managed_array.h"
 #include "sxt/memory/resource/pinned_resource.h"
 #include "sxt/multiexp/pippenger2/partition_table_accessor.h"
@@ -37,8 +38,9 @@ template <class T>
 class in_memory_partition_table_accessor final : public partition_table_accessor<T> {
 
 public:
-  explicit in_memory_partition_table_accessor(std::string_view filename) noexcept
-      : table_{memr::get_pinned_resource()} {
+  explicit in_memory_partition_table_accessor(
+      std::string_view filename, basm::alloc_t alloc = memr::get_pinned_resource()) noexcept
+      : table_{alloc} {
     std::ifstream in{std::string{filename}, std::ios::binary};
     if (!in.good()) {
       baser::panic("failed to open {}: {}", filename, std::strerror(errno));