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silverweedsilverweed
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Add Real32Trunc
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‎types/fundamental/README.md

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* [`integer`](integer): `[U]Int{8,16,32,64}`, `Split[U]Int{16,32,64}`
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* [`misc`](misc): `Bit`, `Byte`, `Char`
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* [`real`](real): `Real{16,32,64}`, `SplitReal{32,64}`
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* [`real32trunc`](real32trunc): `Real32Trunc`
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__Covered under a different category:__
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* `[Split]Index{32,64}`: with [`std::string`](../string) and [`std::vector`](../vector)
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* `Switch`: with [`std::variant`](../variant)
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__Missing:__
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* `Real32Trunc`
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* `Real32Quant`

‎types/fundamental/real32trunc/README.md

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# Real Column Types with variable width and truncated mantissa
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## Fields
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* `FloatReal32Trunc10`
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* `FloatReal32Trunc16`
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* `FloatReal32Trunc31`
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* `DoubleReal32Trunc10`
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* `DoubleReal32Trunc16`
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* `DoubleReal32Trunc31`
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with the corresponding field, column types and bit width.
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## Entries
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1. Ascending values
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2. All 1s in the mantissa
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3. Lowest values with N bits
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4. Smallest positive normal values with N bits
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5. Smallest positive subnormal values with N bits
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6. Maximum values with N bits

‎types/fundamental/real32trunc/read.C

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#include <ROOT/REntry.hxx>
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#include <ROOT/RNTupleReader.hxx>
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using ROOT::Experimental::REntry;
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using ROOT::Experimental::RNTupleReader;
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#include <fstream>
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#include <ios>
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#include <ostream>
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#include <string>
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#include <string_view>
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template <typename T>
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static void PrintRealValue(const REntry &entry, std::string_view name,
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std::ostream &os, bool last = false) {
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T value = *entry.GetPtr<T>(name);
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os << " \"" << name << "\": \"" << value << "\"";
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if (!last) {
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os << ",";
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}
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os << "\n";
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}
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void read(std::string_view input = "types.fundamental.real32trunc.root",
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std::string_view output = "types.fundamental.real32trunc.json") {
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std::ofstream os(std::string{output});
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// Print floating-point numbers as hexadecimal literals.
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os << std::hexfloat;
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os << "[\n";
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auto reader = RNTupleReader::Open("ntpl", input);
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auto &entry = reader->GetModel().GetDefaultEntry();
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bool first = true;
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for (auto index : *reader) {
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reader->LoadEntry(index);
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if (first) {
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first = false;
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} else {
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os << ",\n";
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}
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os << " {\n";
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PrintRealValue<float>(entry, "FloatReal32Trunc10", os);
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PrintRealValue<float>(entry, "FloatReal32Trunc16", os);
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PrintRealValue<float>(entry, "FloatReal32Trunc31", os);
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PrintRealValue<double>(entry, "DoubleReal32Trunc10", os);
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PrintRealValue<double>(entry, "DoubleReal32Trunc16", os);
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PrintRealValue<double>(entry, "DoubleReal32Trunc31", os, /*last=*/true);
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os << " }";
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// Newline is intentionally missing, may need to print a comma before the
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// next entry.
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}
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os << "\n";
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os << "]\n";
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}

‎types/fundamental/real32trunc/write.C

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#include <ROOT/RField.hxx>
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#include <ROOT/RNTupleModel.hxx>
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#include <ROOT/RNTupleUtil.hxx>
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#include <ROOT/RNTupleWriteOptions.hxx>
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#include <ROOT/RNTupleWriter.hxx>
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using ROOT::Experimental::EColumnType;
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using ROOT::Experimental::RField;
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using ROOT::Experimental::RNTupleModel;
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using ROOT::Experimental::RNTupleWriteOptions;
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using ROOT::Experimental::RNTupleWriter;
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#include <limits>
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#include <memory>
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#include <string_view>
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template <typename T>
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static std::shared_ptr<T> MakeFieldReal32Trunc(RNTupleModel &model,
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std::string_view name,
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int nBits) {
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assert(nBits >= 10 && nBits < 32);
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auto field = std::make_unique<RField<T>>(name);
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field->SetTruncated(nBits);
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model.AddField(std::move(field));
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return model.GetDefaultEntry().GetPtr<T>(name);
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}
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void write(std::string_view filename = "types.fundamental.real32trunc.root") {
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auto model = RNTupleModel::Create();
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auto FloatReal32Trunc10 =
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MakeFieldReal32Trunc<float>(*model, "FloatReal32Trunc10", 10);
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auto FloatReal32Trunc16 =
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MakeFieldReal32Trunc<float>(*model, "FloatReal32Trunc16", 16);
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auto FloatReal32Trunc31 =
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MakeFieldReal32Trunc<float>(*model, "FloatReal32Trunc31", 31);
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auto DoubleReal32Trunc10 =
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MakeFieldReal32Trunc<double>(*model, "DoubleReal32Trunc10", 10);
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auto DoubleReal32Trunc16 =
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MakeFieldReal32Trunc<double>(*model, "DoubleReal32Trunc16", 16);
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auto DoubleReal32Trunc31 =
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MakeFieldReal32Trunc<double>(*model, "DoubleReal32Trunc31", 31);
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RNTupleWriteOptions options;
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options.SetCompression(0);
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auto writer =
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RNTupleWriter::Recreate(std::move(model), "ntpl", filename, options);
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// First entry: ascending values
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*FloatReal32Trunc10 = 1.0f;
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*FloatReal32Trunc16 = 2.0f;
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*FloatReal32Trunc31 = 3.0f;
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*DoubleReal32Trunc10 = 4.0f;
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*DoubleReal32Trunc16 = 5.0f;
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*DoubleReal32Trunc31 = 6.0f;
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writer->Fill();
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// Second entry: a value containing all 1s in the mantissa
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static constexpr float Value32 = 3.9999997f;
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*FloatReal32Trunc10 = Value32;
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*FloatReal32Trunc16 = Value32;
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*FloatReal32Trunc31 = Value32;
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*DoubleReal32Trunc10 = Value32;
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*DoubleReal32Trunc16 = Value32;
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*DoubleReal32Trunc31 = Value32;
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writer->Fill();
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// Third entry: lowest values with N bits
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*FloatReal32Trunc10 = -0x1.8p127f;
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*FloatReal32Trunc16 = -0x1.FEp127f;
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*FloatReal32Trunc31 = std::numeric_limits<float>::lowest() + 0x1p-149f;
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*DoubleReal32Trunc10 = -0x1.8p127f;
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*DoubleReal32Trunc16 = -0x1.FEp127;
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*DoubleReal32Trunc31 = std::numeric_limits<float>::lowest() + 0x1p-149f;
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writer->Fill();
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// Fourth entry: min = smallest positive normal values
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*FloatReal32Trunc10 = std::numeric_limits<float>::min();
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*FloatReal32Trunc16 = std::numeric_limits<float>::min();
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*FloatReal32Trunc31 = std::numeric_limits<float>::min();
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*DoubleReal32Trunc10 = std::numeric_limits<float>::min();
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*DoubleReal32Trunc16 = std::numeric_limits<float>::min();
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*DoubleReal32Trunc31 = std::numeric_limits<float>::min();
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writer->Fill();
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// Fifth entry: smallest positive subnormal values with N bits
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// (e.g. FloatReal32Trunc10 has a value with all 0s except a 1 in the 10th bit)
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*FloatReal32Trunc10 = 0x1p-127f;
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*FloatReal32Trunc16 = 0x1p-133f;
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*FloatReal32Trunc31 = 0x1p-148f;
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*DoubleReal32Trunc10 = 0x1p-127f;
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*DoubleReal32Trunc16 = 0x1p-133f;
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*DoubleReal32Trunc31 = 0x1p-148f;
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writer->Fill();
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// Sixth entry: maximum values
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*FloatReal32Trunc10 = 0x1.8p127f;
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*FloatReal32Trunc16 = 0x1.FEp127f;
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*FloatReal32Trunc31 = std::numeric_limits<float>::max() - 0x1p-149f;
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*DoubleReal32Trunc10 = 0x1.8p127f;
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*DoubleReal32Trunc16 = 0x1.FEp127;
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*DoubleReal32Trunc31 = std::numeric_limits<float>::max() - 0x1p-149f;
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writer->Fill();
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}

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