COO sparse tensor contraction produces missing & duplicated entries

[m13253]

The issue

With the following tensor contraction operation (Originated from the CCSD routine used in quantum chemistry):

_a020("aaaa")(p1_va, h3_oa, p3_va, h2_oa) += 0.5 *
    _a004("aaaa")(p2_va, p3_va, h3_oa, h1_oa) * t2_aaaa(p1_va, p2_va, h1_oa, h2_oa)

I generate a C kernel using the following TACO command:

./build/bin/taco \
    'a020aaaa(p1va, p3va, h3oa, h2oa) += 0.5 * a004(p2va, p3va, h3oa, h1oa) * t2aaaa(p1va, p2va, h1oa, h2oa)' \
    -c -f=a020aaaa:uccq -f=a004:uccq -f=t2aaaa:uccq

Then I allocate three COO tensors, each filled with initialization values:

A (of shape [13,  3,  5, 17]) = {0.0, 1.0, 2.0, ..., 3314.0};
B (of shape [ 7, 13, 17, 11]) = {0.0, 1.0, 2.0, ..., 17016.0};
C (of shape [ 7,  3,  5, 11]) = {-1e10, -1e10, -1e10, ..., -1e10};

and call the compute function generated by TACO:

compute(&C, &A, &B);

However, the computation result looks like this:

output[0, 0, 0,  0] = 0.000000
output[0, 0, 0,  1] = 0.000000
...
output[0, 0, 0, 10] = 0.000000
output[0, 0, 0,  0] = 5.500000
output[0, 0, 0,  1] = 6.000000
...
output[0, 0, 0, 10] = 10.500000
output[0, 0, 0,  0] = 22.000000
...
output[0, 1, 1, 10] = 1664.000000

The coordinate [0, 0, 0, 0] repeats multiple times, but the coordinate [1, 0, 0, 0] is missing.
The results are completely incorrect either. The generated kernel completely ignores the += operator and leaks the memory of the data already stored in C.

Minimal reproducible example

I have provided a minimal reproducible example at: https://gist.github.com/m13253/68880026fba40b65936287fbe08766ce

The minimal reproducible example contains four files:

main.c              # Main file
output_correct.txt  # What the output should be, produced using NumPy
output_wrong.txt    # What TACO actually produces
taco_tensor_t.h     # Copied from taco/include/taco/taco_tensor_t.h

Reference commands to build and run the example:

git clone https://gist.github.com/68880026fba40b65936287fbe08766ce.git taco-bug
cd taco-bug

gcc -g -o main -std=c99 -O0 -Wall -Wextra main.c
valgrind --leak-check=full --log-file=leak-check.txt ./main > output.txt

cat output.txt      # Check output tensor
cat leak-check.txt  # Check memory leak report