Move some utils from libiop to libff

CHANGELOG.md

@@ -13,6 +13,7 @@ This update introduces new field and curve API's, and enforces they are used con
 - #83 Make run-clang-tidy return an error when linting fails
 - #85 Add more unit tests for fields (Thanks @alexander-zw)
 - #86 Add binary fields from [libiop](https://github.com/scipr-lab/libiop)
+- #100 Move utils in from [libiop](https://github.com/scipr-lab/libiop)
 
 ### Bug fixes
 - #75 Get rid of warning for unused constant PI, in complex field

libff/CMakeLists.txt

@@ -191,17 +191,30 @@ if ("${IS_LIBFF_PARENT}")
   )
 
   add_executable(
-     algebra_binary_fields_test
-     EXCLUDE_FROM_ALL
+    algebra_binary_fields_test
+    EXCLUDE_FROM_ALL
+
+    algebra/fields/tests/test_binary_fields.cpp
+  )
+  target_link_libraries(
+    algebra_binary_fields_test
+
+    ff
+    gtest_main
+  )
+
+  add_executable(
+    common_test
+    EXCLUDE_FROM_ALL
 
-     algebra/fields/tests/test_binary_fields.cpp
-   )
-   target_link_libraries(
-     algebra_binary_fields_test
+    common/tests/test_common.cpp
+  )
+  target_link_libraries(
+    common_test
 
-     ff
-     gtest_main
-   )
+    ff
+    gtest_main
+  )
 
   include(CTest)
   add_test(
@@ -224,17 +237,22 @@ if ("${IS_LIBFF_PARENT}")
     NAME algebra_fpn_fields_test
     COMMAND algebra_fpn_fields_test
   )
-   add_test(
-     NAME algebra_binary_fields_test
-     COMMAND algebra_binary_fields_test
-   )
+  add_test(
+    NAME algebra_binary_fields_test
+    COMMAND algebra_binary_fields_test
+  )
+  add_test(
+    NAME common_test
+    COMMAND common_test
+  )
 
   add_dependencies(check algebra_bilinearity_test)
   add_dependencies(check algebra_groups_test)
   add_dependencies(check algebra_field_utils_test)
   add_dependencies(check algebra_all_fields_test)
   add_dependencies(check algebra_fpn_fields_test)
   add_dependencies(check algebra_binary_fields_test)
+  add_dependencies(check common_test)
 
   find_package(OpenSSL REQUIRED)
   INCLUDE_DIRECTORIES(${OPENSSL_INCLUDE_DIR})

libff/algebra/field_utils/algorithms.hpp

@@ -25,6 +25,16 @@ FieldT power(const FieldT &base, const bigint<m> &exponent);
 template<typename FieldT>
 FieldT power(const FieldT &base, const unsigned long exponent);
 
+/**
+ * The unsigned long long versions exist because libiop tends to use size_t instead
+ * of unsigned long, and size_t may be the same size as ul or ull.
+ */
+template<typename FieldT>
+FieldT power(const FieldT &base, const unsigned long long exponent);
+
+template<typename FieldT>
+FieldT power(const FieldT &base, const std::vector<unsigned long long> exponent);
+
 /**
  * Tonelli-Shanks square root with given s, t, and quadratic non-residue.
  * Only terminates if there is a square root. Only works if required parameters

libff/algebra/field_utils/algorithms.tcc

@@ -47,6 +47,58 @@ FieldT power(const FieldT &base, const unsigned long exponent)
     return power<FieldT>(base, bigint<1>(exponent));
 }
 
+template<typename FieldT>
+FieldT power(const FieldT &base, const unsigned long long exponent)
+{
+    FieldT result = FieldT::one();
+
+    bool found_one = false;
+
+    for (long i = 8 * sizeof(exponent) - 1; i >= 0; --i)
+    {
+        if (found_one)
+        {
+            result = result.squared();
+        }
+
+        if (exponent & (1ull << i))
+        {
+            found_one = true;
+            result *= base;
+        }
+    }
+
+    return result;
+}
+
+template<typename FieldT>
+FieldT power(const FieldT &base, const std::vector<unsigned long long> exponent)
+{
+    FieldT result = FieldT::one();
+
+    bool found_one = false;
+
+    for (unsigned long long j = 0; j < exponent.size(); j++)
+    {
+        unsigned long long cur_exp = exponent[j];
+        for (long i = 8 * sizeof(cur_exp) - 1; i >= 0; --i)
+        {
+            if (found_one)
+            {
+                result = result.squared();
+            }
+
+            if (cur_exp & (1ull << i))
+            {
+                found_one = true;
+                result *= base;
+            }
+        }
+    }
+
+    return result;
+}
+
 template<typename FieldT>
 FieldT tonelli_shanks_sqrt(const FieldT &value)
 {

libff/algebra/field_utils/field_utils.hpp

@@ -9,12 +9,91 @@
 #define FIELD_UTILS_HPP_
 #include <cstdint>
 
-#include <libff/algebra/field_utils/bigint.hpp>
-#include <libff/common/double.hpp>
-#include <libff/common/utils.hpp>
+#include "libff/algebra/field_utils/bigint.hpp"
+#include "libff/common/double.hpp"
+#include "libff/common/utils.hpp"
+
+#include "libff/algebra/fields/binary/gf64.hpp"
+#include "libff/algebra/fields/binary/gf128.hpp"
+#include "libff/algebra/fields/binary/gf192.hpp"
+#include "libff/algebra/fields/binary/gf256.hpp"
+#include "libff/algebra/fields/prime_base/fp.hpp"
 
 namespace libff {
 
+template<typename FieldT>
+struct is_additive {
+    static const bool value = false;
+};
+
+template<>
+struct is_additive<gf64> {
+    static const bool value = true;
+};
+
+template<>
+struct is_additive<gf128> {
+    static const bool value = true;
+};
+
+template<>
+struct is_additive<gf192> {
+    static const bool value = true;
+};
+
+template<>
+struct is_additive<gf256> {
+    static const bool value = true;
+};
+
+template<typename FieldT>
+struct is_multiplicative {
+    static const bool value = false;
+};
+
+template<mp_size_t n, const bigint<n>& modulus>
+struct is_multiplicative<Fp_model<n, modulus>> {
+    static const bool value = true;
+};
+
+enum field_type {
+    multiplicative_field_type = 1,
+    additive_field_type = 2
+};
+
+template<typename FieldT>
+field_type get_field_type(const typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type elem);
+
+template<typename FieldT>
+field_type get_field_type(const typename enable_if<is_additive<FieldT>::value, FieldT>::type elem);
+
+template<typename FieldT>
+std::size_t log_of_field_size_helper(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem);
+
+template<typename FieldT>
+std::size_t log_of_field_size_helper(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem);
+
+template<typename FieldT>
+std::size_t soundness_log_of_field_size_helper(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem);
+
+template<typename FieldT>
+std::size_t soundness_log_of_field_size_helper(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem);
+
+template<typename FieldT>
+std::size_t get_word_of_field_elem(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem, size_t word);
+
+template<typename FieldT>
+std::size_t get_word_of_field_elem(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem, size_t word);
+
+template<typename FieldT>
+FieldT coset_shift();
+
 // returns root of unity of order n (for n a power of 2), if one exists
 template<typename FieldT>
 typename std::enable_if<std::is_same<FieldT, Double>::value, FieldT>::type

libff/algebra/field_utils/field_utils.tcc

@@ -13,13 +13,76 @@
 #include <complex>
 #include <stdexcept>
 
-#include <libff/common/double.hpp>
-#include <libff/common/utils.hpp>
-
 namespace libff {
 
 using std::size_t;
 
+template<typename FieldT>
+field_type get_field_type(const typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type elem)
+{
+    UNUSED(elem); // only to identify field type
+    return multiplicative_field_type;
+}
+
+template<typename FieldT>
+field_type get_field_type(const typename enable_if<is_additive<FieldT>::value, FieldT>::type elem)
+{
+    UNUSED(elem); // only to identify field type
+    return additive_field_type;
+}
+
+template<typename FieldT>
+std::size_t log_of_field_size_helper(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem)
+{
+    UNUSED(field_elem);
+    return FieldT::ceil_size_in_bits();
+}
+
+template<typename FieldT>
+std::size_t log_of_field_size_helper(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem)
+{
+    UNUSED(field_elem);
+    return FieldT::extension_degree();
+}
+
+template<typename FieldT>
+std::size_t soundness_log_of_field_size_helper(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem)
+{
+    UNUSED(field_elem);
+    /** size in bits is the number of bits needed to represent a field element.
+     *  However there isn't perfect alignment between the number of bits and the number of field elements,
+     *  there could be a factor of two difference.
+     *  For calculating soundness, we use the log of field size as number of bits - 1,
+     *  as (2 << returned) size lower bounds the actual size.
+    */
+    return FieldT::ceil_size_in_bits() - 1;
+}
+
+template<typename FieldT>
+std::size_t soundness_log_of_field_size_helper(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem)
+{
+    UNUSED(field_elem);
+    return FieldT::extension_degree();
+}
+
+template<typename FieldT>
+std::size_t get_word_of_field_elem(
+    typename enable_if<is_additive<FieldT>::value, FieldT>::type field_elem, size_t word)
+{
+    return field_elem.to_words()[word];
+}
+
+template<typename FieldT>
+std::size_t get_word_of_field_elem(
+    typename enable_if<is_multiplicative<FieldT>::value, FieldT>::type field_elem, size_t word)
+{
+    return field_elem.as_bigint().data[word];
+}
+
 template<typename FieldT>
 FieldT coset_shift()
 {

libff/algebra/field_utils/tests/test_field_utils.cpp

@@ -1,16 +1,54 @@
 /**
  *****************************************************************************
- Basic tests for some of the field utils in this directory, mainly bigint.
+ Basic tests for some of the field utils in this directory, mainly bigint
+ and power.
  *****************************************************************************
  * @author     This file is part of libff, developed by SCIPR Lab
  *             and contributors (see AUTHORS).
  * @copyright  MIT license (see LICENSE file)
  *****************************************************************************/
 #include "libff/algebra/field_utils/bigint.hpp"
+#include "libff/algebra/field_utils/algorithms.hpp"
+#include "libff/algebra/fields/binary/gf64.hpp"
 #include <gtest/gtest.h>
 
 using namespace libff;
 
+template<typename FieldT>
+FieldT power_naive(const FieldT &base, const std::size_t exponent)
+{
+    FieldT result = FieldT::one();
+
+    for (std::size_t i = 1; i <= exponent; ++i)
+    {
+        result *= base;
+    }
+
+    return result;
+}
+
+
+TEST(ExponentiationTest, SimpleTest) {
+    typedef gf64 FieldT;
+
+    const unsigned long max_power = 3000;
+    FieldT X = FieldT::random_element();
+
+    FieldT X_i = FieldT::one();
+    for (unsigned long i = 0 ; i < max_power; ++i)
+    {
+        const FieldT X_i_naive = power_naive<FieldT>(X, i);
+        const FieldT X_i_square_and_multiply_ul = power<FieldT>(X, i);
+        const FieldT X_i_square_and_multiply_ull = power<FieldT>(X, (unsigned long long) i);
+
+        EXPECT_EQ(X_i, X_i_naive);
+        EXPECT_EQ(X_i, X_i_square_and_multiply_ul);
+        EXPECT_EQ(X_i, X_i_square_and_multiply_ull);
+
+        X_i *= X;
+    }
+}
+
 TEST(FieldUtilsTest, BigintTest)
 {
     bigint<3> zero = bigint<3>("0");

libff/common/double.cpp

@@ -117,7 +117,7 @@ bool Double::operator==(const Double &other) const
 
 bool Double::operator!=(const Double &other) const
 {
-    return Double(val) != other;
+    return !(*this == other);
 }
 
 bool Double::operator<(const Double &other) const