[GitHub] [incubator-mxnet] haojin2 commented on a change in pull request #14830: [WIP] Use env var to enforce safe accumulation in ReduceAxesCompute

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haojin2 commented on a change in pull request #14830: [WIP] Use env var to enforce safe accumulation in ReduceAxesCompute
URL: https://github.com/apache/incubator-mxnet/pull/14830#discussion_r281834991
 
 

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 File path: docs/faq/env_var.md
 ##########
 @@ -280,6 +280,11 @@ When USE_PROFILER is enabled in Makefile or CMake, the following environments ca
   - Values: Int ```(default=4)```
   - This variable controls how many CuDNN dropout state resources to create for each GPU context for use in operator.
 
+* MXNET_ENFORCE_SAFE_ACCUMULATION
+  - Values: Values: 0(false) or 1(true) ```(default=0)```
+  - If this variable is set, the accumulation will enter the safe mode, meaning accumulation is done in a data type of higher precision than
+    the input data type, leading to more accurate results with a possible performance loss and backward compatibility loss.
 
 Review comment:
   @nswamy Although I agree that using fp32 for fp32 accumulation may be sufficient under many cases, but:
   1. As @eric-haibin-lin said you cannot claim that such accumulation is safe.
   2. Usually a user is not 100% sure that his/her data will not cause overflow during any accumulation, so we want to provide an option if users want to be safe even he/she is using fp32 data type.

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