add AMD bug guard

quest/src/api/qureg.cpp

@@ -168,6 +168,12 @@ Qureg validateAndCreateCustomQureg(int numQubits, int isDensMatr, int useDistrib
     freeAllMemoryIfAnyAllocsFailed(qureg);
     validate_newQuregAllocs(qureg, __func__);
 
+    // TODO / DEBUG:
+    // TEMPORARILY FORBID HIP GPU ACCELERATION OF > 2^32 AMPS PER NODE,
+    // SINCE THIS WILL LEAD TO LATER KERNEL LAUNCH FAILURES; see issue #815
+    if (useGpuAccel && gpu_isHipCompiled() && qureg.numAmpsPerNode >= (1LL << 32))
+        error_quregTooLargeForHipGpuAccel();
+
     // initialise state to |0> or |0><0|
     initZeroState(qureg); 
 

quest/src/core/errors.cpp

@@ -58,6 +58,17 @@ void raiseInternalError(string errorMsg) {
 
 
 
+/*
+ * TEMPORARY / DEBUG ERRORS
+ */
+
+void error_quregTooLargeForHipGpuAccel() {
+
+    raiseInternalError("The created Qureg contains more than 2^32 amplitudes per GPU, which would later trigger a current bug/limitation in QuEST's execution on AMD GPUs. See Github issue #815.");
+}
+
+
+
 /*
  * VALIDATION ERRORS
  */

quest/src/core/errors.hpp

@@ -27,6 +27,14 @@ using std::string;
 
 
 
+/*
+ * TEMPORARY / DEBUG ERRORS
+ */
+
+void error_quregTooLargeForHipGpuAccel();
+
+
+
 /*
  * VALIDATION ERRORS
  */