ggml: add slice example

fundamentals/ggml/src/slice.c

@@ -0,0 +1,63 @@
+#include <stdio.h>
+
+#include "ggml.h"
+#include "ggml-cpu.h"
+#include "ggml-alloc.h"
+#include "ggml-backend.h"
+
+int main(int argc, char **argv) {
+    printf("GGML tensor slice example\n");
+
+    struct ggml_init_params params = {
+        .mem_size   = 16*1024*1024,
+        .mem_buffer = NULL,
+    };
+    struct ggml_context* ctx = ggml_init(params);
+
+    struct ggml_tensor* x = ggml_new_tensor_3d(ctx, GGML_TYPE_F32, 1024, 1025, 1);
+    printf("x ne[0]: %ld\n", x->ne[0]);
+    printf("x ne[1]: %ld\n", x->ne[1]);
+    printf("x ne[2]: %ld\n", x->ne[2]);
+
+    // Calculate the offset to skip the first row
+    size_t offset = x->nb[1];  // Skip one row worth of elements
+    printf("offset: %ld\n", offset);
+
+    /*
+     * z_1
+     *    0 [0                     1023]
+     *      ...
+     *      ...
+     *      ...
+     * 1024 [0                     1023]
+     *
+     * And we want to slice it to similar to the following pytorch code:
+     * x = [:, 1:, :]
+     * This means include everything from the first dimension (;), and
+     * the start from the second element (1:) in the second dimension, and
+     * again include everything in the third dimension (:).
+     *
+     * z_1
+     *    1 [0                     1023]
+     *      ...
+     *      ...
+     *      ...
+     * 1023 [0                     1023]
+     */
+
+    struct ggml_tensor* sliced = ggml_view_3d(ctx, x,
+                                             1024,      // width (features)
+                                             1024,      // height (sequence length after removing first token)
+                                             1,         // depth (batch size)
+                                             x->nb[0],  // row stride (unchanged)
+                                             x->nb[1],  // slice stride (unchanged)
+                                             offset);   // offset to skip first row
+
+    printf("sliced tensor type: %s\n", ggml_type_name(sliced->type));
+    printf("sliced ne[0]: %ld\n", sliced->ne[0]);
+    printf("sliced ne[1]: %ld\n", sliced->ne[1]);
+    printf("sliced ne[2]: %ld\n", sliced->ne[2]);
+
+    ggml_free(ctx);
+    return 0;
+}