Accept string for ArrayInterface constructor.

src/data/array_interface.h

@@ -1,7 +1,7 @@
 /*!
  * Copyright 2019 by Contributors
  * \file array_interface.h
- * \brief Basic structure holding a reference to arrow columnar data format.
+ * \brief View of __array_interface__
  */
 #ifndef XGBOOST_DATA_ARRAY_INTERFACE_H_
 #define XGBOOST_DATA_ARRAY_INTERFACE_H_
@@ -11,6 +11,7 @@
 #include <string>
 #include <utility>
 
+#include "xgboost/base.h"
 #include "xgboost/data.h"
 #include "xgboost/json.h"
 #include "xgboost/logging.h"
@@ -113,6 +114,7 @@ class ArrayInterfaceHandler {
             get<Array const>(
                 obj.at("data"))
             .at(0))));
+    CHECK(p_data);
     return p_data;
   }
 
@@ -186,7 +188,7 @@ class ArrayInterfaceHandler {
     return 0;
   }
 
-  static std::pair<size_t, size_t> ExtractShape(
+  static std::pair<bst_row_t, bst_feature_t> ExtractShape(
       std::map<std::string, Json> const& column) {
     auto j_shape = get<Array const>(column.at("shape"));
     auto typestr = get<String const>(column.at("typestr"));
@@ -201,12 +203,12 @@ class ArrayInterfaceHandler {
     }
 
     if (j_shape.size() == 1) {
-      return {static_cast<size_t>(get<Integer const>(j_shape.at(0))), 1};
+      return {static_cast<bst_row_t>(get<Integer const>(j_shape.at(0))), 1};
     } else {
       CHECK_EQ(j_shape.size(), 2)
           << "Only 1D or 2-D arrays currently supported.";
-      return {static_cast<size_t>(get<Integer const>(j_shape.at(0))),
-              static_cast<size_t>(get<Integer const>(j_shape.at(1)))};
+      return {static_cast<bst_row_t>(get<Integer const>(j_shape.at(0))),
+              static_cast<bst_feature_t>(get<Integer const>(j_shape.at(1)))};
     }
   }
   template <typename T>
@@ -219,7 +221,6 @@ class ArrayInterfaceHandler {
     CHECK_EQ(typestr.at(2),   static_cast<char>(sizeof(T) + 48))
         << "Input data type and typestr mismatch. typestr: " << typestr;
 
-
     auto shape = ExtractShape(column);
 
     T* p_data = ArrayInterfaceHandler::GetPtrFromArrayData<T*>(column);
@@ -229,10 +230,8 @@ class ArrayInterfaceHandler {
 
 // A view over __array_interface__
 class ArrayInterface {
- public:
-  ArrayInterface() = default;
-  explicit ArrayInterface(std::map<std::string, Json> const &column,
-                          bool allow_mask = true) {
+  void Initialize(std::map<std::string, Json> const &column,
+                  bool allow_mask = true) {
     ArrayInterfaceHandler::Validate(column);
     data = ArrayInterfaceHandler::GetPtrFromArrayData<void*>(column);
     CHECK(data) << "Column is null";
@@ -263,6 +262,27 @@ class ArrayInterface {
     this->CheckType();
   }
 
+ public:
+  ArrayInterface() = default;
+  explicit ArrayInterface(std::string const& str, bool allow_mask = true) {
+    auto jinterface = Json::Load({str.c_str(), str.size()});
+    if (IsA<Object>(jinterface)) {
+      this->Initialize(get<Object const>(jinterface), allow_mask);
+      return;
+    }
+    if (IsA<Array>(jinterface)) {
+      CHECK_EQ(get<Array const>(jinterface).size(), 1)
+          << "Column: " << ArrayInterfaceErrors::Dimension(1);
+      this->Initialize(get<Object const>(get<Array const>(jinterface)[0]), allow_mask);
+      return;
+    }
+  }
+
+  explicit ArrayInterface(std::map<std::string, Json> const &column,
+                          bool allow_mask = true) {
+    this->Initialize(column, allow_mask);
+  }
+
   void CheckType() const {
     if (type[1] == 'f' && type[2] == '4') {
       return;
@@ -291,6 +311,7 @@ class ArrayInterface {
   }
 
   XGBOOST_DEVICE float GetElement(size_t idx) const {
+    SPAN_CHECK(idx < num_cols * num_rows);
     if (type[1] == 'f' && type[2] == '4') {
       return reinterpret_cast<float*>(data)[idx];
     } else if (type[1] == 'f' && type[2] == '8') {
@@ -318,8 +339,8 @@ class ArrayInterface {
   }
 
   RBitField8 valid;
-  int32_t num_rows;
-  int32_t num_cols;
+  bst_row_t num_rows;
+  bst_feature_t num_cols;
   void* data;
   char type[3];
 };

src/data/data.cu

@@ -63,7 +63,7 @@ void MetaInfo::SetInfo(const char * c_key, std::string const& interface_str) {
   auto const& j_arr = get<Array>(j_interface);
   CHECK_EQ(j_arr.size(), 1)
       << "MetaInfo: " << c_key << ". " << ArrayInterfaceErrors::Dimension(1);
-  ArrayInterface array_interface(get<Object const>(j_arr[0]));
+  ArrayInterface array_interface(interface_str);
   std::string key{c_key};
   CHECK(!array_interface.valid.Data())
       << "Meta info " << key << " should be dense, found validity mask";

tests/cpp/data/test_array_interface.cc

@@ -0,0 +1,51 @@
+/*!
+ * Copyright 2020 by XGBoost Contributors
+ */
+#include <gtest/gtest.h>
+#include <xgboost/host_device_vector.h>
+#include "../helpers.h"
+#include "../../../src/data/array_interface.h"
+
+namespace xgboost {
+TEST(ArrayInterface, Initialize) {
+  size_t constexpr kRows = 10, kCols = 10;
+  HostDeviceVector<float> storage;
+  auto array = RandomDataGenerator{kRows, kCols, 0}.GenerateArrayInterface(&storage);
+  auto arr_interface = ArrayInterface(array);
+  ASSERT_EQ(arr_interface.num_rows, kRows);
+  ASSERT_EQ(arr_interface.num_cols, kCols);
+  ASSERT_EQ(arr_interface.data, storage.ConstHostPointer());
+}
+
+TEST(ArrayInterface, Error) {
+  constexpr size_t kRows = 16, kCols = 10;
+  Json column { Object() };
+  std::vector<Json> j_shape {Json(Integer(static_cast<Integer::Int>(kRows)))};
+  column["shape"] = Array(j_shape);
+  std::vector<Json> j_data {
+    Json(Integer(reinterpret_cast<Integer::Int>(nullptr))),
+        Json(Boolean(false))};
+
+  auto const& column_obj = get<Object>(column);
+  // missing version
+  EXPECT_THROW(ArrayInterfaceHandler::ExtractData<float>(column_obj), dmlc::Error);
+  column["version"] = Integer(static_cast<Integer::Int>(1));
+  // missing data
+  EXPECT_THROW(ArrayInterfaceHandler::ExtractData<float>(column_obj), dmlc::Error);
+  column["data"] = j_data;
+  // missing typestr
+  EXPECT_THROW(ArrayInterfaceHandler::ExtractData<float>(column_obj), dmlc::Error);
+  column["typestr"] = String("<f4");
+  // nullptr is not valid
+  EXPECT_THROW(ArrayInterfaceHandler::ExtractData<float>(column_obj), dmlc::Error);
+
+  HostDeviceVector<float> storage;
+  auto array = RandomDataGenerator{kRows, kCols, 0}.GenerateArrayInterface(&storage);
+  j_data = {
+      Json(Integer(reinterpret_cast<Integer::Int>(storage.ConstHostPointer()))),
+      Json(Boolean(false))};
+  column["data"] = j_data;
+  EXPECT_NO_THROW(ArrayInterfaceHandler::ExtractData<float>(column_obj));
+}
+
+}  // namespace xgboost

tests/cpp/helpers.cc

@@ -182,7 +182,13 @@ Json RandomDataGenerator::ArrayInterfaceImpl(HostDeviceVector<float> *storage,
   this->GenerateDense(storage);
   Json array_interface {Object()};
   array_interface["data"] = std::vector<Json>(2);
-  array_interface["data"][0] = Integer(reinterpret_cast<int64_t>(storage->DevicePointer()));
+  if (storage->DeviceCanRead()) {
+    array_interface["data"][0] =
+        Integer(reinterpret_cast<int64_t>(storage->ConstDevicePointer()));
+  } else {
+    array_interface["data"][0] =
+        Integer(reinterpret_cast<int64_t>(storage->ConstHostPointer()));
+  }
   array_interface["data"][1] = Boolean(false);
 
   array_interface["shape"] = std::vector<Json>(2);