tests : check DT3 byte positions against hand-computed literals

The previous byte-position test packed with the test's own packer on
both sides of the comparison, so it exercised none of the library code.
It now pins hand-computed byte values (43/100/127/42/124...) at the
region boundaries (79/80, 119/120) as ground truth and drives both
directions through the library: to_float must place each literal byte's
trit at the exact element, and from_float must produce the exact literal
byte, for both planes.

Also probes ggml_validate_row_data over all 256 byte values in qs and
qh positions (must accept exactly the 243/81 reachable codes), the
all-0xaa block, and a well-formed packed block.

ggml/src/ggml-quants.c

@@ -2554,7 +2554,8 @@ void quantize_row_dt3_ref(const float * GGML_RESTRICT x, block_dt3 * GGML_RESTRI
             d1 = amax;
             const float id = d1 ? 1.0f/d1 : 0.0f;
             for (int j = 0; j < QK_DT3; j++) {
-                t1[j] = (int8_t) lroundf(x[j] * id); // -1, 0, 1
+                const int v = (int) lroundf(x[j] * id); // -1, 0, 1 (clamp guards against NaN input)
+                t1[j] = (int8_t) MAX(-1, MIN(1, v));
             }
         }
 
@@ -2567,7 +2568,8 @@ void quantize_row_dt3_ref(const float * GGML_RESTRICT x, block_dt3 * GGML_RESTRI
             d2 = amax;
             const float id = d2 ? 1.0f/d2 : 0.0f;
             for (int j = 0; j < QK_DT3; j++) {
-                t2[j] = (int8_t) lroundf((x[j] - d1*t1[j]) * id); // -1, 0, 1
+                const int v = (int) lroundf((x[j] - d1*t1[j]) * id); // -1, 0, 1 (clamp guards against NaN input)
+                t2[j] = (int8_t) MAX(-1, MIN(1, v));
             }
         }
 
@@ -2611,7 +2613,15 @@ void quantize_row_dt3_ref(const float * GGML_RESTRICT x, block_dt3 * GGML_RESTRI
 }
 
 size_t quantize_dt3(const float * GGML_RESTRICT src, void * GGML_RESTRICT dst, int64_t nrow, int64_t n_per_row, const float * quant_weights) {
-    (void)quant_weights; // not used
+    if (quant_weights) {
+        // say it loudly, or an imatrix-vs-no-imatrix A/B on DT3 would come out
+        // byte-identical and someone would conclude the imatrix does nothing
+        static bool warned = false;
+        if (!warned) {
+            fprintf(stderr, "%s: WARNING: imatrix ignored: the DT3 reference quantizer does not use it; quality comes from ternaria's PTQTP\n", __func__);
+            warned = true;
+        }
+    }
     const size_t row_size = ggml_row_size(GGML_TYPE_DT3, n_per_row);
     quantize_row_dt3_ref(src, dst, (int64_t)nrow*n_per_row);
     return nrow * row_size;
@@ -5796,6 +5806,29 @@ bool ggml_validate_row_data(enum ggml_type type, const void * data, size_t nbyte
                     if (!validate_fp16(q[i].d[0], i) || !validate_fp16(q[i].d[1], i)) {
                         return false;
                     }
+                    // the ceiling-division packing reaches only 243 of the 256
+                    // byte values in qs, and only 81 in qh (4 trits plus an
+                    // always-zero padding digit); anything else is corruption,
+                    // and a corrupted block would otherwise load and generate
+                    // garbage without any warning
+                    for (int p = 0; p < 2; ++p) {
+                        for (size_t j = 0; j < sizeof(q[i].qs[p]); ++j) {
+                            const uint32_t b = q[i].qs[p][j];
+                            const uint32_t v = (b*243) >> 8; // inverse of the ceiling division
+                            if ((v*256 + 242)/243 != b) {
+                                fprintf(stderr, "ggml_validate_row_data: found invalid dt3 qs byte 0x%02x at block %zu\n", (unsigned) b, i);
+                                return false;
+                            }
+                        }
+                        for (size_t j = 0; j < sizeof(q[i].qh[p]); ++j) {
+                            const uint32_t b = q[i].qh[p][j];
+                            const uint32_t v = (b*243) >> 8;
+                            if (v % 3 != 0 || (v*256 + 242)/243 != b) {
+                                fprintf(stderr, "ggml_validate_row_data: found invalid dt3 qh byte 0x%02x at block %zu\n", (unsigned) b, i);
+                                return false;
+                            }
+                        }
+                    }
                 }
             } break;
         case GGML_TYPE_IQ1_S:

src/llama-quant.cpp

@@ -884,6 +884,11 @@ static void llama_model_quantize_impl(const std::string & fname_inp, const std::
         throw std::runtime_error(format("invalid output file type %d\n", ftype));
     }
 
+    if (ftype == LLAMA_FTYPE_MOSTLY_DT3) {
+        LLAMA_LOG_WARN("%s: DT3 is being quantized with the in-tree REFERENCE quantizer only - "
+                       "the measured DT3 quality requires the planes from ternaria's PTQTP pipeline\n", __func__);
+    }
+
     // mmap consistently increases speed on Linux, and also increases speed on Windows with
     // hot cache. It may cause a slowdown on macOS, possibly related to free memory.
 #if defined(__linux__) || defined(_WIN32)

tests/test-dt3.cpp

@@ -143,53 +143,117 @@ static int test_single_trits(const ggml_type_traits * qfns) {
     return num_failed;
 }
 
-// spot-check the byte positions of the region boundaries against values
-// computed by hand from the packing formula
-static int test_byte_positions(void) {
+// an all-zero plane packs to qs = 128, qh = 127 everywhere (hand-computed:
+// qs: xi = 1 for the 5 trits -> q = 121 -> ceil(121*256/243) = 128,
+// qh: q = 40*3 = 120 -> ceil(120*256/243) = 127)
+constexpr uint8_t ZERO_QS = 128;
+constexpr uint8_t ZERO_QH = 127;
+
+static void build_zero_pattern_block(uint8_t * block, float d1, float d2) {
+    memset(block + OFF_QS, ZERO_QS, 2*DT3_QS_BYTES);
+    memset(block + OFF_QH, ZERO_QH, 2*DT3_QH_BYTES);
+    const uint16_t h1 = ggml_fp32_to_fp16(d1);
+    const uint16_t h2 = ggml_fp32_to_fp16(d2);
+    memcpy(block + OFF_D,     &h1, sizeof(h1));
+    memcpy(block + OFF_D + 2, &h2, sizeof(h2));
+}
+
+// check the byte positions of the region boundaries against literal values
+// computed by hand from the packing formula (and cross-checked one by one
+// against an independent implementation of the spec). Both directions go
+// against the LIBRARY code — to_float and from_float — never against a
+// packer defined in this file, so a bit-placement bug in ggml-quants.c
+// cannot cancel out.
+static int test_byte_positions(const ggml_type_traits * qfns, const ggml_type_traits_cpu * qfns_cpu) {
     int num_failed = 0;
 
-    // verify the element -> byte mapping structurally: flipping element `pos`
-    // must change EXACTLY the one byte the formula says, and no other
-    struct pos_case {
-        int    pos;
-        size_t off; // expected changed byte, offset inside plane data
+    struct byte_case {
+        int     pos;   // element with t = -1, all others 0
+        size_t  off;   // byte offset inside the plane data (qs: 0..23, qh: 24, 25)
+        uint8_t value; // hand-computed byte value at that offset
     };
-    const pos_case pcases[] = {
-        {   0, 0  }, // region A, byte 0
-        {  15, 15 }, // region A, byte 15
-        {  16, 0  }, // region A, digit 1 of byte 0
-        {  64, 0  }, // region A, digit 4 of byte 0
-        {  79, 15 }, // region A boundary: last element, byte 15
-        {  80, 16 }, // region B boundary: first element, byte 16
-        {  87, 23 }, // region B, byte 23
-        { 119, 23 }, // region B boundary: last element, byte 23
-        { 120, 24 }, // region C boundary: first element, qh[0]
-        { 121, 25 }, // region C, qh[1]
-        { 126, 24 }, // region C, digit 3 of qh[0]
-        { 127, 25 }, // region C, last element, qh[1]
+    const byte_case cases[] = {
+        {   0,  0,  43 }, // region A: most significant trit of qs[0]:  q = 121-81 = 40  -> 43
+        {  16,  0, 100 }, // region A: second trit of qs[0]:            q = 121-27 = 94  -> 100
+        {  79, 15, 127 }, // region A boundary: last trit of qs[15]:    q = 121-1  = 120 -> 127
+        {  80, 16,  43 }, // region B boundary: first trit of qs[16]:   q = 40           -> 43
+        { 119, 23, 127 }, // region B boundary: last trit of qs[23]:    q = 120          -> 127
+        { 120, 24,  42 }, // region C boundary: first trit of qh[0]:    q = (40-27)*3    -> 42
+        { 127, 25, 124 }, // region C: last element, qh[1]:             q = (40-1)*3     -> 124
     };
 
-    uint8_t zero_plane[DT3_QS_BYTES + DT3_QH_BYTES];
-    {
-        const int8_t t0[QK_DT3] = {0};
-        ref_pack_plane(t0, zero_plane, zero_plane + DT3_QS_BYTES);
+    for (size_t c = 0; c < sizeof(cases)/sizeof(cases[0]); ++c) {
+        const int     pos = cases[c].pos;
+        const size_t  off = cases[c].off;
+        const uint8_t val = cases[c].value;
+
+        // unpack direction: writing the literal byte must put -1 at exactly
+        // element `pos` of the corresponding plane
+        for (int plane = 0; plane < 2; ++plane) {
+            uint8_t block[DT3_BLOCK_SIZE];
+            build_zero_pattern_block(block, 1.0f, 0.25f);
+            if (off < DT3_QS_BYTES) {
+                block[OFF_QS + plane*DT3_QS_BYTES + off] = val;
+            } else {
+                block[OFF_QH + plane*DT3_QH_BYTES + (off - DT3_QS_BYTES)] = val;
+            }
+
+            float out[QK_DT3];
+            qfns->to_float(block, out, QK_DT3);
+
+            const float dp = plane == 0 ? 1.0f : 0.25f;
+            for (int j = 0; j < QK_DT3; ++j) {
+                const float expected = j == pos ? -dp : 0.0f;
+                if (out[j] != expected) {
+                    printf("FAILED: byte 0x%02x at plane %d offset %zu: out[%d] = %f, expected %f\n",
+                           val, plane, off, j, out[j], expected);
+                    num_failed++;
+                }
+            }
+        }
+
+        // pack direction: quantizing a single -1 must produce exactly the
+        // literal byte at the right offset of plane 0 (plane 1 is the zero
+        // pattern since there is no residual), and nothing else
+        {
+            float x[QK_DT3] = {0.0f};
+            x[pos] = -1.0f;
+
+            uint8_t block[DT3_BLOCK_SIZE];
+            qfns_cpu->from_float(x, block, QK_DT3);
+
+            uint8_t expected[DT3_BLOCK_SIZE];
+            build_zero_pattern_block(expected, 1.0f, 0.0f);
+            if (off < DT3_QS_BYTES) {
+                expected[OFF_QS + off] = val;
+            } else {
+                expected[OFF_QH + (off - DT3_QS_BYTES)] = val;
+            }
+
+            for (size_t b = 0; b < DT3_BLOCK_SIZE; ++b) {
+                if (block[b] != expected[b]) {
+                    printf("FAILED: pack of -1 at element %d: byte %zu is 0x%02x, expected 0x%02x\n",
+                           pos, b, block[b], expected[b]);
+                    num_failed++;
+                }
+            }
+        }
     }
 
-    for (size_t c = 0; c < sizeof(pcases)/sizeof(pcases[0]); ++c) {
-        int8_t t[QK_DT3] = {0};
-        t[pcases[c].pos] = -1;
+    // all-zero input packs to the all-zero pattern with zero scales
+    {
+        const float x[QK_DT3] = {0.0f};
 
-        uint8_t plane[DT3_QS_BYTES + DT3_QH_BYTES];
-        ref_pack_plane(t, plane, plane + DT3_QS_BYTES);
+        uint8_t block[DT3_BLOCK_SIZE];
+        qfns_cpu->from_float(x, block, QK_DT3);
 
-        for (size_t b = 0; b < sizeof(plane); ++b) {
-            const bool should_differ = b == pcases[c].off;
-            const bool differs       = plane[b] != zero_plane[b];
-            if (differs != should_differ) {
-                printf("FAILED: pos %d: byte %zu %s, expected %s\n",
-                       pcases[c].pos, b,
-                       differs ? "changed" : "unchanged",
-                       should_differ ? "changed" : "unchanged");
+        uint8_t expected[DT3_BLOCK_SIZE];
+        build_zero_pattern_block(expected, 0.0f, 0.0f);
+
+        for (size_t b = 0; b < DT3_BLOCK_SIZE; ++b) {
+            if (block[b] != expected[b]) {
+                printf("FAILED: pack of all-zero block: byte %zu is 0x%02x, expected 0x%02x\n",
+                       b, block[b], expected[b]);
                 num_failed++;
             }
         }
@@ -198,6 +262,73 @@ static int test_byte_positions(void) {
     return num_failed;
 }
 
+// ggml_validate_row_data must accept exactly the reachable byte values:
+// 243 of 256 in qs, 81 of 256 in qh (4 trits + an always-zero padding digit)
+static int test_validate(void) {
+    int num_failed = 0;
+
+    bool valid_qs[256] = {false};
+    bool valid_qh[256] = {false};
+    for (uint32_t q = 0; q < 243; ++q) {
+        valid_qs[(q*256 + 242)/243] = true;
+        if (q % 3 == 0 && q <= 240) {
+            valid_qh[(q*256 + 242)/243] = true;
+        }
+    }
+
+    printf("(invalid-byte messages below are expected, the validator is being probed)\n");
+
+    for (int b = 0; b < 256; ++b) {
+        uint8_t block[DT3_BLOCK_SIZE];
+
+        build_zero_pattern_block(block, 1.0f, 0.25f);
+        block[OFF_QS] = (uint8_t) b;
+        if (ggml_validate_row_data(GGML_TYPE_DT3, block, DT3_BLOCK_SIZE) != valid_qs[b]) {
+            printf("FAILED: validate qs byte 0x%02x: expected %s\n", b, valid_qs[b] ? "valid" : "invalid");
+            num_failed++;
+        }
+
+        build_zero_pattern_block(block, 1.0f, 0.25f);
+        block[OFF_QH + DT3_QH_BYTES] = (uint8_t) b; // plane 1 qh, to also cover the second plane
+        if (ggml_validate_row_data(GGML_TYPE_DT3, block, DT3_BLOCK_SIZE) != valid_qh[b]) {
+            printf("FAILED: validate qh byte 0x%02x: expected %s\n", b, valid_qh[b] ? "valid" : "invalid");
+            num_failed++;
+        }
+    }
+
+    // a block filled with 0xaa must be rejected (0xaa is a reachable qs code
+    // but violates the qh padding-digit invariant)
+    {
+        uint8_t block[DT3_BLOCK_SIZE];
+        memset(block, 0xaa, DT3_BLOCK_SIZE);
+        const uint16_t h = ggml_fp32_to_fp16(1.0f);
+        memcpy(block + OFF_D,     &h, sizeof(h));
+        memcpy(block + OFF_D + 2, &h, sizeof(h));
+        if (ggml_validate_row_data(GGML_TYPE_DT3, block, DT3_BLOCK_SIZE)) {
+            printf("FAILED: validate accepted a block filled with 0xaa\n");
+            num_failed++;
+        }
+    }
+
+    // packed real data must pass
+    {
+        int8_t t1[QK_DT3];
+        int8_t t2[QK_DT3];
+        for (int j = 0; j < QK_DT3; ++j) {
+            t1[j] = rng_trit();
+            t2[j] = rng_trit();
+        }
+        uint8_t block[DT3_BLOCK_SIZE];
+        ref_pack_block(t1, -0.5f, t2, 0.125f, block);
+        if (!ggml_validate_row_data(GGML_TYPE_DT3, block, DT3_BLOCK_SIZE)) {
+            printf("FAILED: validate rejected a well-formed block\n");
+            num_failed++;
+        }
+    }
+
+    return num_failed;
+}
+
 // random trits and scales (negative scales included) must round-trip exactly
 static int test_roundtrip(const ggml_type_traits * qfns) {
     int num_failed = 0;
@@ -405,7 +536,8 @@ int main(int argc, char * argv[]) {
 
     num_failed += test_layout_constants();
     num_failed += test_single_trits(qfns);
-    num_failed += test_byte_positions();
+    num_failed += test_byte_positions(qfns, qfns_cpu);
+    num_failed += test_validate();
     num_failed += test_roundtrip(qfns);
     num_failed += test_quantize_pack_parity(qfns_cpu);
     num_failed += test_vec_dot(qfns_cpu);