test(linalg): GPU correctness coverage for Kron and Outer (#1003, confirms #999) by yingjerkao · Pull Request #1100 · Cytnx-dev/Cytnx

yingjerkao · 2026-07-20T04:45:16Z

Problem

Kron and Outer had no GPU tests — their CUDA paths (cuKron_internal.cuh, cuOuter_internal.cu) were entirely uncovered. This is the coverage the #1003 Outer/Kron typed-dispatch consolidation needs as a safety net, and it also confirms #999 is resolved.

Fix

Add tests/gpu/linalg_test/Kron_test.cpp and Outer_test.cpp. Expected values are computed independently from the operation definition (literals or per-element recompute), not by comparing against another Cytnx path that could share the same bug:

Double / ComplexDouble — hand-written literal results (Kron also covers fractional + negative values).
Mixed ComplexFloat × Double → ComplexDouble — the promotion discriminator behind GPU build broken: cuKron fails to compile (CUDA 13) after the #982 type_promote change #999/fix(linalg): replace lower-enum-index dtype selection with Type.type_promote #984: the product must be computed and stored through the promoted output type. Checks output dtype and value.
Broad GPU-vs-CPU cross-check over every real/complex dtype as secondary coverage. ComplexFloat uses a looser tolerance because ~1e6-magnitude float32 complex products diverge from the CPU at the ULP; a single real multiply is bit-identical.

Inputs are built on the CPU and moved with .to(Device.cuda) (GPU arange ignores a non-unit step for real dtypes, #1070).

Testing

All 9 tests pass on an RTX 4070 Ti SUPER (CUDA 13.0, sm_89):

[  PASSED  ] 9 tests.   (GpuKron: 5, GpuOuter: 4)

Verified against a build with the parent commit's Outer_ii fix applied (the Outer cross-check's CPU reference needs the Int16/Uint16 dispatch rows). The cuKron/cuOuter/Kron.cpp/Outer.cpp sources under test are identical to origin/master.

Notes

Stacked on fix(linalg): register missing Int16/Uint16/Bool rows in CPU Outer dispatch (fixes segfault) #1099 (the CPU Outer Int16/Uint16/Bool dispatch fix). The Outer GPU cross-check's CPU reference crashes without it. Will retarget to master once fix(linalg): register missing Int16/Uint16/Bool rows in CPU Outer dispatch (fixes segfault) #1099 merges.
No GPU CI runner exists, so these compile/run only under a local USE_CUDA build (as done here).

Part of #1003. Confirms #999.

Kron and Outer had no GPU tests. Add tests/gpu/linalg_test/Kron_test.cpp and Outer_test.cpp exercising the GPU paths with independently hand-computed expected values (not GPU-vs-CPU as the primary oracle): - Double and ComplexDouble with literal and per-element-recomputed results (Kron also covers fractional/negative values); - the mixed ComplexFloat x Double -> ComplexDouble promotion discriminator (output dtype AND value), the case that motivated #999 / #984 -- the product must be computed and stored through the promoted output type; - a broad GPU-vs-CPU cross-check over every real/complex dtype as secondary coverage (ComplexFloat gets a looser tolerance because ~1e6-magnitude float32 complex products diverge from the CPU one at the ULP; a single real multiply is bit-identical). Inputs are built on the CPU and moved with .to(Device.cuda) since GPU arange ignores a non-unit step for real dtypes (#1070). The Outer cross-check's CPU reference relies on the Int16/Uint16 Outer dispatch fix in the parent commit; without it those dtypes crash. Testing: all 9 tests pass on an RTX 4070 Ti SUPER (CUDA 13.0, sm_89). This also confirms #999 (the GPU library builds clean and Kron is numerically correct). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

gemini-code-assist

Code Review

This pull request adds GPU test suites for the Kronecker product (Kron) and outer product (Outer) linear algebra operations, verifying correctness across various data types, fractional/negative values, complex numbers, and type promotions. The reviewer feedback focuses on adhering to the repository's style guide by replacing legacy cytnx_XXXX typedefs (such as cytnx_uint64 and cytnx_double) with standard C++ types (like uint64_t and double) for loop counters, local variables, and lambda parameters in the newly added test files.

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gemini-code-assist · 2026-07-20T04:46:32Z

+        for (cytnx_uint64 i = 0; i < 4; i++)
+          for (cytnx_uint64 j = 0; j < 4; j++)


Avoid using legacy typedefs like cytnx_uint64 for ordinary loop counters in new code. Use standard C++ types such as uint64_t or size_t instead.

Suggested change

for (cytnx_uint64 i = 0; i < 4; i++)

for (cytnx_uint64 j = 0; j < 4; j++)

for (uint64_t i = 0; i < 4; i++)

for (uint64_t j = 0; j < 4; j++)

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        const cytnx_uint64 bR = 2, bC = 3;
+        for (cytnx_uint64 i = 0; i < 6; i++)
+          for (cytnx_uint64 j = 0; j < 6; j++) {


Avoid using legacy typedefs like cytnx_uint64 for local sizes and loop counters in new code. Standard C++ types like uint64_t or size_t are preferred.

Suggested change

const cytnx_uint64 bR = 2, bC = 3;

for (cytnx_uint64 i = 0; i < 6; i++)

for (cytnx_uint64 j = 0; j < 6; j++) {

const uint64_t bR = 2, bC = 3;

for (uint64_t i = 0; i < 6; i++)

for (uint64_t j = 0; j < 6; j++) {

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        // out[i,j] = a[0, j] * b[i, 0]
+        // (1+1i)*(0+1i) = -1+1i ; (2-1i)*(0+1i) = 1+2i
+        // (1+1i)*(3+0i) =  3+3i ; (2-1i)*(3+0i) = 6-3i
+        auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {


Avoid using legacy typedefs like cytnx_uint64 for lambda parameters representing indices in new code. Use standard C++ types like uint64_t instead.

Suggested change

auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {

auto near = [&](uint64_t i, uint64_t j, double re, double im) {

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        ASSERT_EQ(out.dtype(), Type.ComplexDouble);
+        ASSERT_EQ(out.shape(), (std::vector<cytnx_uint64>{2, 2}));
+        // out[i,j] = a[i,0] * b[0,j]
+        auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {


Avoid using legacy typedefs like cytnx_uint64 for lambda parameters representing indices in new code. Use standard C++ types like uint64_t instead.

Suggested change

auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {

auto near = [&](uint64_t i, uint64_t j, double re, double im) {

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+          if (dtype == Type.Bool) continue;  // Kron has no Bool kernel
+          // See Outer_test's note: ~1e6-magnitude complex-float products diverge
+          // from the CPU at the float32 ULP, so ComplexFloat gets a looser tol.
+          const cytnx_double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;


Avoid using legacy typedefs like cytnx_double for local arithmetic types such as tolerance variables in new code. Use standard C++ types like double instead.

Suggested change

const cytnx_double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;

const double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        for (cytnx_uint64 i = 0; i < 3; i++)
+          for (cytnx_uint64 j = 0; j < 2; j++)


Avoid using legacy typedefs like cytnx_uint64 for ordinary loop counters in new code. Use standard C++ types such as uint64_t or size_t instead.

Suggested change

for (cytnx_uint64 i = 0; i < 3; i++)

for (cytnx_uint64 j = 0; j < 2; j++)

for (uint64_t i = 0; i < 3; i++)

for (uint64_t j = 0; j < 2; j++)

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        ASSERT_EQ(out.shape(), (std::vector<cytnx_uint64>{2, 2}));
+        // (1+2i)*(0-1i) = 2-1i ; (1+2i)*(2+2i) = -2+6i
+        // (-3+1i)*(0-1i)= 1+3i ; (-3+1i)*(2+2i)= -8-4i
+        auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {


Avoid using legacy typedefs like cytnx_uint64 for lambda parameters representing indices in new code. Use standard C++ types like uint64_t instead.

Suggested change

auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {

auto near = [&](uint64_t i, uint64_t j, double re, double im) {

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+
+        ASSERT_EQ(out.dtype(), Type.ComplexDouble);
+        ASSERT_EQ(out.shape(), (std::vector<cytnx_uint64>{2, 2}));
+        auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {


Avoid using legacy typedefs like cytnx_uint64 for lambda parameters representing indices in new code. Use standard C++ types like uint64_t instead.

Suggested change

auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {

auto near = [&](uint64_t i, uint64_t j, double re, double im) {

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

gemini-code-assist · 2026-07-20T04:46:33Z

+        for (auto dtype : dtype_list) {
+          if (dtype == Type.Bool) continue;  // Outer has no Bool kernel
+          SCOPED_TRACE("dtype " + std::to_string(dtype));
+          const cytnx_double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;


Avoid using legacy typedefs like cytnx_double for local arithmetic types such as tolerance variables in new code. Use standard C++ types like double instead.

Suggested change

const cytnx_double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;

const double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;

References

Avoid propagating legacy cytnx_XXXX typedefs as ordinary loop counters, sizes, flags, or local arithmetic types in new or touched code. Prefer standard C++ types. ^(link)

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chatgpt-codex-connector · 2026-07-20T04:48:44Z

+        b.at<cytnx_double>({0, 0}) = 2.0;
+        b.at<cytnx_double>({0, 1}) = -0.5;


Use precision-sensitive doubles in this discriminator

In this mixed-promotion regression test, the Double operands are exactly representable as float, and the expected tolerance is loose enough that an implementation which still narrows the multiply to complex64 before producing a ComplexDouble result would pass with these values. That leaves the stated “full double precision” behavior untested for the ComplexFloat × Double path; use a non-float-representable double or a magnitude/cancellation case whose result changes after float narrowing.

Useful? React with 👍 / 👎.

chatgpt-codex-connector · 2026-07-20T04:48:44Z

+        b.at<cytnx_double>({0}) = 3;
+        b.at<cytnx_double>({1}) = 0.5;


Use precision-sensitive doubles in this discriminator

This mixed-promotion test also uses Double values that are exactly representable as float, so it only verifies the dtype and not the promised full-double computation path. If the GPU path accidentally multiplies in complex64 and then writes/casts to ComplexDouble, these expected values still pass within 1e-6; choose a non-float-representable double value or another case whose product differs after float narrowing.

Useful? React with 👍 / 👎.

yingjerkao · 2026-07-22T02:16:28Z

Closing — its GPU test coverage has been salvaged into #1108, and the rest is superseded by #1105/#1106.

Background: this PR was stacked on the (now-closed) #1099 branch, and the Outer→Kron rewrite + GPU test files it depended on already landed on master via #1105/#1106 — so it can't merge as-is (it would try to re-apply changes already present and conflict).

But its tests were more thorough than what landed, so rather than lose them, #1108 folds this PR's stronger cases into master's existing tests/gpu/linalg_test/{Kron,Outer}_test.cpp:

2-D hand-computed Kron/Outer (fractional + negative values),
complex × complex hand-computed cases,
the ComplexFloat × Double → ComplexDouble promotion discriminator,
the broad GPU-vs-CPU all-dtype differential (GpuMatchesCpuAllDtypes),

while keeping master's Int16 hand-computed Kron and the #1099 Int16-diagonal Outer segfault guard. Verified on GPU (CUDA 13, RTX 4070 Ti): 11/11 pass. Thanks!

gemini-code-assist Bot reviewed Jul 20, 2026

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yingjerkao mentioned this pull request Jul 20, 2026

refactor(linalg): typed GPU dispatch for Outer + retire Kron GPU promotion trait (#1003) #1101

Closed

yingjerkao requested review from IvanaGyro and ianmccul July 20, 2026 08:02

yingjerkao mentioned this pull request Jul 22, 2026

test(linalg): strengthen GPU Kron/Outer coverage (salvaged from #1100) #1108

Open

yingjerkao closed this Jul 22, 2026

		for (cytnx_uint64 i = 0; i < 4; i++)
		for (cytnx_uint64 j = 0; j < 4; j++)

	auto near = [&](cytnx_uint64 i, cytnx_uint64 j, double re, double im) {
	auto near = [&](uint64_t i, uint64_t j, double re, double im) {

	const cytnx_double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;
	const double tol = (dtype == Type.ComplexFloat) ? 0.1 : 1e-6;

		for (cytnx_uint64 i = 0; i < 3; i++)
		for (cytnx_uint64 j = 0; j < 2; j++)

		b.at<cytnx_double>({0, 0}) = 2.0;
		b.at<cytnx_double>({0, 1}) = -0.5;

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