fix(android): add support for amerabi-v7a (arm NEON 32bit); fixes #30

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
   build:
     runs-on: ${{ matrix.os }}
     container: ${{ matrix.container && matrix.container || '' }}
-    name: ${{ matrix.name }}${{ matrix.arch && format('-{0}', matrix.arch) || '' }} build${{ matrix.arch != 'arm64-v8a' && matrix.name != 'ios-sim' && matrix.name != 'ios' && matrix.name != 'apple-xcframework' && matrix.name != 'android-aar' && ( matrix.name != 'macos' || matrix.arch != 'x86_64' ) && ' + test' || ''}}
+    name: ${{ matrix.name }}${{ matrix.arch && format('-{0}', matrix.arch) || '' }} build${{ matrix.arch != 'arm64-v8a' && matrix.arch != 'armeabi-v7a' && matrix.name != 'ios-sim' && matrix.name != 'ios' && matrix.name != 'apple-xcframework' && matrix.name != 'android-aar' && ( matrix.name != 'macos' || matrix.arch != 'x86_64' ) && ' + test' || ''}}
     timeout-minutes: 20
     strategy:
       fail-fast: false
@@ -47,6 +47,10 @@ jobs:
             arch: arm64-v8a
             name: android
             make: PLATFORM=android ARCH=arm64-v8a
+          - os: ubuntu-22.04
+            arch: armeabi-v7a
+            name: android
+            make: PLATFORM=android ARCH=armeabi-v7a
           - os: ubuntu-22.04
             arch: x86_64
             name: android
@@ -140,7 +144,7 @@ jobs:
           security delete-keychain build.keychain
 
       - name: android setup test environment
-        if: matrix.name == 'android' && matrix.arch != 'arm64-v8a'
+        if: matrix.name == 'android' && matrix.arch != 'arm64-v8a' && matrix.arch != 'armeabi-v7a'
         run: |
 
           echo "::group::enable kvm group perms"
@@ -168,7 +172,7 @@ jobs:
           echo "::endgroup::"
 
       - name: android test sqlite-vector
-        if: matrix.name == 'android' && matrix.arch != 'arm64-v8a'
+        if: matrix.name == 'android' && matrix.arch != 'arm64-v8a' && matrix.arch != 'armeabi-v7a'
         uses: reactivecircus/android-emulator-runner@v2.34.0
         with:
           api-level: 26

Makefile

@@ -59,16 +59,22 @@ else ifeq ($(PLATFORM),macos)
 	STRIP = strip -x -S $@
 else ifeq ($(PLATFORM),android)
 	ifndef ARCH # Set ARCH to find Android NDK's Clang compiler, the user should set the ARCH
-		$(error "Android ARCH must be set to ARCH=x86_64 or ARCH=arm64-v8a")
+		$(error "Android ARCH must be set to ARCH=x86_64, ARCH=arm64-v8a, or ARCH=armeabi-v7a")
 	endif
 	ifndef ANDROID_NDK # Set ANDROID_NDK path to find android build tools; e.g. on MacOS: export ANDROID_NDK=/Users/username/Library/Android/sdk/ndk/25.2.9519653
 		$(error "Android NDK must be set")
 	endif
 	BIN = $(ANDROID_NDK)/toolchains/llvm/prebuilt/$(HOST)-x86_64/bin
 	ifneq (,$(filter $(ARCH),arm64 arm64-v8a))
 		override ARCH := aarch64
+		ANDROID_ABI := android26
+	else ifeq ($(ARCH),armeabi-v7a)
+		override ARCH := armv7a
+		ANDROID_ABI := androideabi26
+	else
+		ANDROID_ABI := android26
 	endif
-	CC = $(BIN)/$(ARCH)-linux-android26-clang
+	CC = $(BIN)/$(ARCH)-linux-$(ANDROID_ABI)-clang
 	TARGET := $(DIST_DIR)/vector.so
 	LDFLAGS += -lm -shared
 	STRIP = $(BIN)/llvm-strip --strip-unneeded $@
@@ -184,11 +190,14 @@ $(DIST_DIR)/%.xcframework: $(LIB_NAMES)
 
 xcframework: $(DIST_DIR)/vector.xcframework
 
-AAR_ARM = packages/android/src/main/jniLibs/arm64-v8a/
+AAR_ARM64 = packages/android/src/main/jniLibs/arm64-v8a/
+AAR_ARM = packages/android/src/main/jniLibs/armeabi-v7a/
 AAR_X86 = packages/android/src/main/jniLibs/x86_64/
 aar:
-	mkdir -p $(AAR_ARM) $(AAR_X86)
+	mkdir -p $(AAR_ARM64) $(AAR_ARM) $(AAR_X86)
 	$(MAKE) clean && $(MAKE) PLATFORM=android ARCH=arm64-v8a
+	mv $(DIST_DIR)/vector.so $(AAR_ARM64)
+	$(MAKE) clean && $(MAKE) PLATFORM=android ARCH=armeabi-v7a
 	mv $(DIST_DIR)/vector.so $(AAR_ARM)
 	$(MAKE) clean && $(MAKE) PLATFORM=android ARCH=x86_64
 	mv $(DIST_DIR)/vector.so $(AAR_X86)
@@ -208,7 +217,7 @@ help:
 	@echo "  linux (default on Linux)"
 	@echo "  macos (default on macOS)"
 	@echo "  windows (default on Windows)"
-	@echo "  android (needs ARCH to be set to x86_64 or arm64-v8a and ANDROID_NDK to be set)"
+	@echo "  android (needs ARCH to be set to x86_64, arm64-v8a, or armeabi-v7a and ANDROID_NDK to be set)"
 	@echo "  ios (only on macOS)"
 	@echo "  ios-sim (only on macOS)"
 	@echo ""

src/distance-neon.c

@@ -13,11 +13,27 @@
 
 
 #if defined(__ARM_NEON) || defined(__ARM_NEON__)
+
+#if __SIZEOF_POINTER__ == 4
+#define _ARM32BIT_ 1
+#endif
+
 #include <arm_neon.h>
 
 extern distance_function_t dispatch_distance_table[VECTOR_DISTANCE_MAX][VECTOR_TYPE_MAX];
 extern char *distance_backend_name;
 
+// Helper function for 32-bit ARM: vmaxv_u16 is not available in ARMv7 NEON
+#ifdef _ARM32BIT_
+static inline uint16_t vmaxv_u16_compat(uint16x4_t v) {
+    // Use pairwise max to reduce vector
+    uint16x4_t m = vpmax_u16(v, v);  // [max(v0,v1), max(v2,v3), max(v0,v1), max(v2,v3)]
+    m = vpmax_u16(m, m);              // [max(all), max(all), max(all), max(all)]
+    return vget_lane_u16(m, 0);
+}
+#define vmaxv_u16 vmaxv_u16_compat
+#endif
+
 // MARK: FLOAT32 -
 
 float float32_distance_l2_impl_neon (const void *v1, const void *v2, int n, bool use_sqrt) {
@@ -158,6 +174,31 @@ float bfloat16_distance_l2_impl_neon (const void *v1, const void *v2, int n, boo
     const uint16_t *a = (const uint16_t *)v1;
     const uint16_t *b = (const uint16_t *)v2;
 
+#ifdef _ARM32BIT_
+    // 32-bit ARM: use scalar double accumulation (no float64x2_t in NEON)
+    double sum = 0.0;
+    int i = 0;
+
+    for (; i <= n - 4; i += 4) {
+        uint16x4_t av16 = vld1_u16(a + i);
+        uint16x4_t bv16 = vld1_u16(b + i);
+
+        float32x4_t va = bf16x4_to_f32x4_u16(av16);
+        float32x4_t vb = bf16x4_to_f32x4_u16(bv16);
+        float32x4_t d  = vsubq_f32(va, vb);
+        // mask-out NaNs: m = (d==d)
+        uint32x4_t m   = vceqq_f32(d, d);
+        d = vbslq_f32(m, d, vdupq_n_f32(0.0f));
+
+        // Store and accumulate in scalar double
+        float tmp[4];
+        vst1q_f32(tmp, d);
+        for (int j = 0; j < 4; j++) {
+            double dj = (double)tmp[j];
+            sum = fma(dj, dj, sum);
+        }
+    }
+#else
     // Accumulate in f64 to avoid overflow from huge bf16 values.
     float64x2_t acc0 = vdupq_n_f64(0.0), acc1 = vdupq_n_f64(0.0);
     int i = 0;
@@ -205,6 +246,7 @@ float bfloat16_distance_l2_impl_neon (const void *v1, const void *v2, int n, boo
     }
 
     double sum = vaddvq_f64(vaddq_f64(acc0, acc1));
+#endif
 
     // scalar tail; treat NaN as 0, Inf as +Inf result
     for (; i < n; ++i) {
@@ -409,8 +451,15 @@ float float16_distance_l2_impl_neon (const void *v1, const void *v2, int n, bool
     const uint16x4_t SIGN_MASK = vdup_n_u16(0x8000u);
     const uint16x4_t ZERO16    = vdup_n_u16(0);
 
+#ifdef _ARM32BIT_
+    // 32-bit ARM: use scalar double accumulation
+    double sum = 0.0;
+    int i = 0;
+#else
+    // 64-bit ARM: use float64x2_t NEON intrinsics
     float64x2_t acc0 = vdupq_n_f64(0.0), acc1 = vdupq_n_f64(0.0);
     int i = 0;
+#endif
 
     for (; i <= n - 4; i += 4) {
         uint16x4_t av16 = vld1_u16(a + i);
@@ -443,6 +492,16 @@ float float16_distance_l2_impl_neon (const void *v1, const void *v2, int n, bool
         uint32x4_t m = vceqq_f32(d32, d32);                    /* true where not-NaN */
         d32 = vbslq_f32(m, d32, vdupq_n_f32(0.0f));
 
+#ifdef _ARM32BIT_
+        // 32-bit ARM: accumulate in scalar double
+        float tmp[4];
+        vst1q_f32(tmp, d32);
+        for (int j = 0; j < 4; j++) {
+            double dj = (double)tmp[j];
+            sum = fma(dj, dj, sum);
+        }
+#else
+        // 64-bit ARM: use NEON f64 operations
         float64x2_t dlo = vcvt_f64_f32(vget_low_f32(d32));
         float64x2_t dhi = vcvt_f64_f32(vget_high_f32(d32));
 #if defined(__ARM_FEATURE_FMA)
@@ -451,10 +510,13 @@ float float16_distance_l2_impl_neon (const void *v1, const void *v2, int n, bool
 #else
         acc0 = vaddq_f64(acc0, vmulq_f64(dlo, dlo));
         acc1 = vaddq_f64(acc1, vmulq_f64(dhi, dhi));
+#endif
 #endif
     }
 
+#ifndef _ARM32BIT_
     double sum = vaddvq_f64(vaddq_f64(acc0, acc1));
+#endif
 
     /* tail (scalar; same Inf/NaN policy) */
     for (; i < n; ++i) {
@@ -487,10 +549,17 @@ float float16_distance_cosine_neon (const void *v1, const void *v2, int n) {
     const uint16x4_t FRAC_MASK = vdup_n_u16(0x03FFu);
     const uint16x4_t ZERO16    = vdup_n_u16(0);
 
+#ifdef _ARM32BIT_
+    // 32-bit ARM: use scalar double accumulation
+    double dot = 0.0, normx = 0.0, normy = 0.0;
+    int i = 0;
+#else
+    // 64-bit ARM: use float64x2_t NEON intrinsics
     float64x2_t acc_dot_lo = vdupq_n_f64(0.0), acc_dot_hi = vdupq_n_f64(0.0);
     float64x2_t acc_a2_lo  = vdupq_n_f64(0.0), acc_a2_hi  = vdupq_n_f64(0.0);
     float64x2_t acc_b2_lo  = vdupq_n_f64(0.0), acc_b2_hi  = vdupq_n_f64(0.0);
     int i = 0;
+#endif
 
     for (; i <= n - 4; i += 4) {
         uint16x4_t av16 = vld1_u16(a + i);
@@ -512,6 +581,19 @@ float float16_distance_cosine_neon (const void *v1, const void *v2, int n) {
         ax = vbslq_f32(mx, ax, vdupq_n_f32(0.0f));
         by = vbslq_f32(my, by, vdupq_n_f32(0.0f));
 
+#ifdef _ARM32BIT_
+        // 32-bit ARM: accumulate in scalar double
+        float ax_tmp[4], by_tmp[4];
+        vst1q_f32(ax_tmp, ax);
+        vst1q_f32(by_tmp, by);
+        for (int j = 0; j < 4; j++) {
+            double x = (double)ax_tmp[j];
+            double y = (double)by_tmp[j];
+            dot += x * y;
+            normx += x * x;
+            normy += y * y;
+        }
+#else
         /* widen to f64 and accumulate */
         float64x2_t ax_lo = vcvt_f64_f32(vget_low_f32(ax)), ax_hi = vcvt_f64_f32(vget_high_f32(ax));
         float64x2_t by_lo = vcvt_f64_f32(vget_low_f32(by)), by_hi = vcvt_f64_f32(vget_high_f32(by));
@@ -530,12 +612,15 @@ float float16_distance_cosine_neon (const void *v1, const void *v2, int n) {
         acc_a2_hi  = vaddq_f64(acc_a2_hi,  vmulq_f64(ax_hi, ax_hi));
         acc_b2_lo  = vaddq_f64(acc_b2_lo,  vmulq_f64(by_lo, by_lo));
         acc_b2_hi  = vaddq_f64(acc_b2_hi,  vmulq_f64(by_hi, by_hi));
+#endif
 #endif
     }
 
+#ifndef _ARM32BIT_
     double dot  = vaddvq_f64(vaddq_f64(acc_dot_lo, acc_dot_hi));
     double normx= vaddvq_f64(vaddq_f64(acc_a2_lo,  acc_a2_hi));
     double normy= vaddvq_f64(vaddq_f64(acc_b2_lo,  acc_b2_hi));
+#endif
 
     /* tail (scalar) */
     for (; i < n; ++i) {
@@ -569,8 +654,15 @@ float float16_distance_dot_neon (const void *v1, const void *v2, int n) {
     const uint16x4_t FRAC_MASK = vdup_n_u16(0x03FFu);
     const uint16x4_t ZERO16    = vdup_n_u16(0);
 
+#ifdef _ARM32BIT_
+    // 32-bit ARM: use scalar double accumulation
+    double dot = 0.0;
+    int i = 0;
+#else
+    // 64-bit ARM: use float64x2_t NEON intrinsics
     float64x2_t acc_lo = vdupq_n_f64(0.0), acc_hi = vdupq_n_f64(0.0);
     int i = 0;
+#endif
 
     for (; i <= n - 4; i += 4) {
         uint16x4_t av16 = vld1_u16(a + i);
@@ -588,7 +680,11 @@ float float16_distance_dot_neon (const void *v1, const void *v2, int n) {
                 if (isnan(x) || isnan(y)) continue;
                 double p = (double)x * (double)y;
                 if (isinf(p)) return (p>0)? -INFINITY : INFINITY;
+#ifdef _ARM32BIT_
+                dot += p;
+#else
                 acc_lo = vsetq_lane_f64(vgetq_lane_f64(acc_lo,0)+p, acc_lo, 0); /* cheap add */
+#endif
             }
             continue;
         }
@@ -603,13 +699,26 @@ float float16_distance_dot_neon (const void *v1, const void *v2, int n) {
         by = vbslq_f32(my, by, vdupq_n_f32(0.0f));
 
         float32x4_t prod = vmulq_f32(ax, by);
+
+#ifdef _ARM32BIT_
+        // 32-bit ARM: accumulate in scalar double
+        float prod_tmp[4];
+        vst1q_f32(prod_tmp, prod);
+        for (int j = 0; j < 4; j++) {
+            dot += (double)prod_tmp[j];
+        }
+#else
+        // 64-bit ARM: use NEON f64 operations
         float64x2_t lo = vcvt_f64_f32(vget_low_f32(prod));
         float64x2_t hi = vcvt_f64_f32(vget_high_f32(prod));
         acc_lo = vaddq_f64(acc_lo, lo);
         acc_hi = vaddq_f64(acc_hi, hi);
+#endif
     }
 
+#ifndef _ARM32BIT_
     double dot = vaddvq_f64(vaddq_f64(acc_lo, acc_hi));
+#endif
 
     for (; i < n; ++i) {
         float x = float16_to_float32(a[i]);
@@ -635,8 +744,15 @@ float float16_distance_l1_neon (const void *v1, const void *v2, int n) {
     const uint16x4_t SIGN_MASK = vdup_n_u16(0x8000u);
     const uint16x4_t ZERO16    = vdup_n_u16(0);
 
+#ifdef _ARM32BIT_
+    // 32-bit ARM: use scalar double accumulation
+    double sum = 0.0;
+    int i = 0;
+#else
+    // 64-bit ARM: use float64x2_t NEON intrinsics
     float64x2_t acc = vdupq_n_f64(0.0);
     int i = 0;
+#endif
 
     for (; i <= n - 4; i += 4) {
         uint16x4_t av16 = vld1_u16(a + i);
@@ -665,13 +781,25 @@ float float16_distance_l1_neon (const void *v1, const void *v2, int n) {
         uint32x4_t m   = vceqq_f32(d, d);                   /* mask NaNs -> 0 */
         d = vbslq_f32(m, d, vdupq_n_f32(0.0f));
 
+#ifdef _ARM32BIT_
+        // 32-bit ARM: accumulate in scalar double
+        float tmp[4];
+        vst1q_f32(tmp, d);
+        for (int j = 0; j < 4; j++) {
+            sum += (double)tmp[j];
+        }
+#else
+        // 64-bit ARM: use NEON f64 operations
         float64x2_t lo = vcvt_f64_f32(vget_low_f32(d));
         float64x2_t hi = vcvt_f64_f32(vget_high_f32(d));
         acc = vaddq_f64(acc, lo);
         acc = vaddq_f64(acc, hi);
+#endif
     }
 
+#ifndef _ARM32BIT_
     double sum = vaddvq_f64(acc);
+#endif
 
     for (; i < n; ++i) {
         uint16_t ai=a[i], bi=b[i];