Template Deduction Problem when adding equivalence check in std::enable_if - c++

Question

I am trying to benchmark different ways to sum. I'd like using an interface as follows
avx2_sum<sum_algorithm::normal>(container.begin(), container.end());
However, my attempt
enum class sum_algorithm: char{
normal,
kahan,
twofold_fast //https://arxiv.org/pdf/1401.0248.pdf
};
template<sum_algorithm algorithm_t, typename iterator_t, typename sum_t = typename std::iterator_traits<iterator_t>::value_type,
std::enable_if_t<std::is_same<sum_t, double>::value && (algorithm_t == sum_algorithm::normal)> = true>
sum_t avx2_sum(const iterator_t begin, const iterator_t end) noexcept {
// SIMD-parallel summation stage
auto running_sums = _mm256_set1_pd(0);
auto iterator_skip = 256/sizeof(sum_t);
for (iterator_t it = begin; it + iterator_skip < end; it += iterator_skip){
//TODO: flip to double load reduction
running_sums = _mm256_add_pd(_mm256_load_pd(it), running_sums);
}
// Serial summation
running_sums = _mm256_hadd_pd(running_sums, running_sums);
running_sums = _mm256_hadd_pd(running_sums, running_sums);
return _mm256_cvtsd_f64(running_sums);
}
produces the following:
error: no matching function for call to 'avx2_sum'
std::cout << "avx2<float, normal>: " << accumulators::avx2_sum<algo::normal>(float_arr.begin(), float_arr.end()) <<"\n";
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/rlfactory/dev/thommmj1/cppbenchmarks/cpp_utils/algorithms/cpu_accumulators.hpp:55:11: note: candidate template ignored: requirement 'std::is_same<float, double>::value' was not satisfied [with algorithm_t = accumulators::sum_algorithm::normal, iterator_t = __gnu_cxx::__normal_iterator<float *, std::vector<float, std::allocator<float> > >, sum_t = float]
sum_t avx2_sum(const iterator_t begin, const iterator_t end) noexcept {
^
/home/rlfactory/dev/thommmj1/cppbenchmarks/cpp_utils/algorithms/cpu_accumulators.hpp:71:11: note: candidate template ignored: substitution failure [with algorithm_t = accumulators::sum_algorithm::normal, iterator_t = __gnu_cxx::__normal_iterator<float *, std::vector<float, std::allocator<float> > >, sum_t = float]: a non-type template parameter cannot have type 'std::enable_if_t<std::is_same<float, float>::value && ((sum_algorithm)'\x00' == sum_algorithm::normal)>' (aka 'void')
sum_t avx2_sum(const iterator_t begin, const iterator_t end) noexcept {
^
/home/rlfactory/dev/thommmj1/cppbenchmarks/cpp_utils/algorithms/cpu_accumulators.hpp:87:11: note: candidate template ignored: requirement 'std::is_same<float, double>::value' was not satisfied [with algorithm_t = accumulators::sum_algorithm::normal, iterator_t = __gnu_cxx::__normal_iterator<float *, std::vector<float, std::allocator<float> > >, sum_t = float]
sum_t avx2_sum(const iterator_t begin, const iterator_t end) noexcept {
^
/home/rlfactory/dev/thommmj1/cppbenchmarks/cpp_utils/algorithms/cpu_accumulators.hpp:109:11: note: candidate template ignored: requirement 'std::is_same<float, float>::value && ((accumulators::sum_algorithm)'\x00' == sum_algorithm::kahan)' was not satisfied [with algorithm_t = accumulators::sum_algorithm::normal, iterator_t = __gnu_cxx::__normal_iterator<float *, std::vector<float, std::allocator<float> > >, sum_t = float]
sum_t avx2_sum(const iterator_t begin, const iterator_t end) noexcept {
I don't understand how deduction doesn't work here. Without the algorithm_t template portion and check, it works just fine. Perhaps it's due to my using statement? using algo = accumulators::sum_algorithm;