ggml : add GGML_OP_COL2IM_1D (#24206)

* cpu: add GGML_OP_COL2IM_1D

Add the overlap-add (scatter-add) step of a 1D transposed convolution.
A ConvTranspose1d factorizes as a GEMM followed by col2im: a weight
pre-permuted to [IC, K*OC] is contracted against the [IC, T_in] input
with mul_mat to produce a column matrix [K*OC, T_in], and col2im_1d
scatters those columns back into the [T_out, OC] signal, with
T_out = (T_in - 1)*s0 + K - 2*p0.

Keeping the contraction as a plain mul_mat leaves the heavy work on the
optimized (and quantizable) matmul kernels, so col2im_1d only does the
cheap overlap-add.

CPU uses a gather formulation parallelized over output channels,
supporting F32, F16 and BF16 with an F32 accumulator.

* tests: add backend coverage for GGML_OP_COL2IM_1D

Add test_col2im_1d next to the conv_transpose_1d cases, covering F32,
F16 and BF16 across eight geometries: the canonical kernel = 2*stride
DAC upsampling shape, overlap, no overlap, cropping (p0 = 1 and
p0 = stride/2), kernel < stride with zeroed gaps, kernel not a
multiple of stride, and a single column unfold.

Perf mode gets three real vocoder stage shapes reporting memory
bandwidth. max_nmse_err relaxes to 5e-4 for F16 and BF16.

* cpu: harden GGML_OP_COL2IM_1D

ggml_col2im_1d validates s0, oc, p0 and input contiguity at graph
build time, before the oc division, protecting every backend at once.
The kernel asserts the contiguity its flat indexing assumes and its
doc states the full output length including the crop term.

The kernel parallelizes over the time axis: the split stays balanced
down to OC = 1, where the previous channel split was single threaded.
Values are bit identical on the three real vocoder chains, two out of
three improve.

* tests: extend the GGML_OP_COL2IM_1D grid

The eval grid grows to eleven geometries: OC = 1 (mono output stage),
K = 1 with stride > 1 (sparse scatter, every gap position zeroed) and
a crop down to T_out = 2 where all the gather bounds act at once.

* tests: add col2im_1d equivalence test

tests/test-col2im-1d.cpp proves mul_mat + col2im_1d matches the
native ggml_conv_transpose_1d on the CPU backend, F32 bit exact, F16
and BF16 through casts of the column matrix. test-backend-ops cannot
cover this for a CPU only op since the CPU backend is its own
reference there.

* rpc: bump protocol patch version for GGML_OP_COL2IM_1D

GGML_OP_COUNT goes from 96 to 97 with the new op, which trips the
static_assert in ggml-rpc.h. Bump RPC_PROTO_PATCH_VERSION since the
op is appended and no existing op code shifts.

tests/test-backend-ops.cpp

@@ -5098,6 +5098,39 @@ struct test_conv_transpose_1d : public test_case {
     }
 };
 
+// GGML_OP_COL2IM_1D
+struct test_col2im_1d : public test_case {
+    const ggml_type type;
+    const int64_t K;    // kernel size
+    const int64_t OC;   // output channels
+    const int64_t T_in; // input length (number of columns)
+    const int s0;       // stride
+    const int p0;       // padding cropped from both sides
+
+    std::string vars() override {
+        return VARS_TO_STR6(type, K, OC, T_in, s0, p0);
+    }
+
+    double max_nmse_err() override {
+        return type == GGML_TYPE_F32 ? 1e-7 : 5e-4;
+    }
+
+    test_col2im_1d(ggml_type type = GGML_TYPE_F32,
+            int64_t K = 4, int64_t OC = 3, int64_t T_in = 7,
+            int s0 = 2, int p0 = 0)
+        : type(type), K(K), OC(OC), T_in(T_in), s0(s0), p0(p0) {}
+
+    ggml_tensor * build_graph(ggml_context * ctx) override {
+        ggml_tensor * cols = ggml_new_tensor_2d(ctx, type, K*OC, T_in);
+        ggml_set_name(cols, "cols");
+
+        ggml_tensor * out = ggml_col2im_1d(ctx, cols, s0, (int) OC, p0);
+        ggml_set_name(out, "out");
+
+        return out;
+    }
+};
+
 // GGML_OP_CONV_TRANSPOSE_2D
 struct test_conv_transpose_2d : public test_case {
     // Dimensions
@@ -8013,6 +8046,21 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
     test_cases.emplace_back(new test_conv_transpose_1d({3,2,1,1}, {3,1,2,1}, 1, 0, 1));
     test_cases.emplace_back(new test_conv_transpose_1d({2,1,1,1}, {3,1,1,1}, 1, 0, 1));
 
+    for (ggml_type type : {GGML_TYPE_F32, GGML_TYPE_F16, GGML_TYPE_BF16}) {
+        // ConvTranspose1d expressed as mul_mat + col2im (DAC decoder upsampling)
+        test_cases.emplace_back(new test_col2im_1d(type, 16, 32, 197, 8, 0)); // kernel = 2*stride
+        test_cases.emplace_back(new test_col2im_1d(type, 4, 3, 7, 2, 0));
+        test_cases.emplace_back(new test_col2im_1d(type, 1, 5, 13, 1, 0));    // stride 1, no overlap
+        test_cases.emplace_back(new test_col2im_1d(type, 6, 4, 11, 3, 1));    // with cropping
+        test_cases.emplace_back(new test_col2im_1d(type, 2, 3, 9, 3, 0));     // kernel < stride, gap positions are zeroed
+        test_cases.emplace_back(new test_col2im_1d(type, 5, 4, 11, 2, 0));    // kernel not a multiple of stride, alternating overlap
+        test_cases.emplace_back(new test_col2im_1d(type, 8, 4, 13, 4, 2));    // padding = stride/2 (DAC causal cropping)
+        test_cases.emplace_back(new test_col2im_1d(type, 4, 3, 1, 2, 0));     // single column, pure kernel unfold
+        test_cases.emplace_back(new test_col2im_1d(type, 16, 1, 197, 8, 0));   // OC = 1, mono output stage
+        test_cases.emplace_back(new test_col2im_1d(type, 1, 5, 13, 3, 0));     // K = 1 with stride > 1, sparse scatter
+        test_cases.emplace_back(new test_col2im_1d(type, 8, 2, 3, 2, 5));      // cropping eats most of the signal, T_out = 2
+    }
+
     for (ggml_type kernel_type : {GGML_TYPE_F32, GGML_TYPE_F16}) {
         test_cases.emplace_back(new test_conv_transpose_2d({3, 2, 3, 1}, {2, 2, 1, 3}, 1, kernel_type));
         test_cases.emplace_back(new test_conv_transpose_2d({10, 10, 9, 1}, {3, 3, 1, 9}, 2, kernel_type));
@@ -9366,6 +9414,11 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_perf() {
         test_cases.emplace_back(new test_conv_transpose_2d({10, 10, 9, 1}, {3, 3, 1, 9}, 2, kernel_type));
     }
 
+    // Memory bound overlap-add of the GEMM + col2im_1d transposed conv path, real vocoder stage shapes
+    test_cases.emplace_back(new test_col2im_1d(GGML_TYPE_F32, 16, 512, 2048, 8, 0));
+    test_cases.emplace_back(new test_col2im_1d(GGML_TYPE_F32, 4, 128, 65536, 2, 0));
+    test_cases.emplace_back(new test_col2im_1d(GGML_TYPE_F16, 16, 512, 2048, 8, 0));
+
     test_cases.emplace_back(new test_mean(GGML_TYPE_F32, {256, 256, 3, 1}));