ggml : fix null ptr deref in backward pass

ggml.c

@@ -13605,9 +13605,6 @@ static void ggml_compute_backward(struct ggml_context * ctx, struct ggml_tensor
                                     src0),
                                 inplace);
                 }
-                if (src1->grad) {
-                    // not supported
-                }
             } break;
         case GGML_OP_SUM:
             {

tests/test-grad0.c

@@ -38,9 +38,7 @@
 
 #define GGML_PRINT(...) printf(__VA_ARGS__)
 
-
-
-float frand() {
+float frand(void) {
     return (float)rand()/(float)RAND_MAX;
 }
 
@@ -856,7 +854,6 @@ int main(int argc, const char ** argv) {
         // set_2d
         {
             int64_t ne2[4];
-            int64_t nb2[4];
             int64_t max_offsets[4] = { 0, 0, 0, 0 };
             int64_t offsets[4]     = { 0, 0, 0, 0 };
 

tests/test-opt.c

@@ -191,6 +191,13 @@ int main(int argc, const char ** argv) {
 // main: original  e = 1620817.8750
 // main: optimized e = 698387.6875
 
+// another run on M1
+// int64_t ne1[4] = {4, 1024, 1, 1};
+// int64_t ne2[4] = {4, 2048, 1, 1};;
+// int64_t ne3[4] = {1024, 2048, 1, 1};
+// main: original  e = 1629595.6250
+// main: optimized e = 698169.1250
+
 // int64_t ne1[4] = {32, 1024, 1, 1};
 // int64_t ne2[4] = {32, 2048, 1, 1};;
 // int64_t ne3[4] = {1024, 2048, 1, 1};