Don't crash Python interpreter via assert(false) (#998)

bitsandbytes/functional.py

@@ -1944,7 +1944,10 @@ def igemmlt(A, B, SA, SB, out=None, Sout=None, dtype=torch.int32):
                 ptr, m, n, k, ptrA, ptrB, ptrC, ptrRowScale, lda, ldb, ldc
             )
 
-    if has_error == 1:
+    if has_error == 100:  # `ERR_NOT_IMPLEMENTED` is defined as 100 in `ops.cu`
+        raise NotImplementedError("igemmlt not available (probably built with NO_CUBLASLT)")
+
+    if has_error:
         print(f'A: {shapeA}, B: {shapeB}, C: {Sout[0]}; (lda, ldb, ldc): {(lda, ldb, ldc)}; (m, n, k): {(m, n, k)}')
         raise Exception('cublasLt ran into an error!')
 

csrc/ops.cu

@@ -11,6 +11,8 @@
 #include <cassert>
 #include <common.h>
 
+#define ERR_NOT_IMPLEMENTED 100
+
 
 using namespace BinSearch;
 using std::cout;
@@ -421,14 +423,7 @@ template void transform<int32_t, COL32, ROW, false, 32>(cublasLtHandle_t ltHandl
 template <int FORMATB, int DTYPE_OUT, int SCALE_ROWS> int igemmlt(cublasLtHandle_t ltHandle, int m, int n, int k, const int8_t *A, const int8_t *B, void *C, float *row_scale, int lda, int ldb, int ldc)
 {
 #ifdef NO_CUBLASLT
-  cout << "" << endl;
-  cout << "=============================================" << endl;
-  cout << "ERROR: Your GPU does not support Int8 Matmul!" << endl;
-  cout << "=============================================" << endl;
-  cout << "" << endl;
-  assert(false);
-
-	return 0;
+	return ERR_NOT_IMPLEMENTED;
 #else
     int has_error = 0;
     cublasLtMatmulDesc_t matmulDesc = NULL;
@@ -484,7 +479,7 @@ template <int FORMATB, int DTYPE_OUT, int SCALE_ROWS> int igemmlt(cublasLtHandle
       printf("error detected");
 
     return has_error;
-#endif
+#endif // NO_CUBLASLT
 }
 
 int fill_up_to_nearest_multiple(int value, int multiple)