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Update c++ readers doc #9352
Update c++ readers doc #9352
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@@ -113,7 +113,7 @@ To solve this problem, we introduce `ReaderHolder` as a wrapper. It acts as an e | |
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To create and invoke readers, some new ops are introduced: | ||
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### CreateReaderOp | ||
### Operators That Creates Readers | ||
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Each reader has its creation op. File readers' creation ops have no input and yield the created file reader as its output. Decorated readers' creation ops take the underlying readers as inputs and then yield new decorated readers. | ||
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@@ -153,13 +153,17 @@ double_buffer_reader = create_double_buffer_op(batch_reader) | |
The forwarding ops of the corresponding `main_program` would be like this: | ||
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``` | ||
while_op { | ||
not_completed = true | ||
pass_count = 0 | ||
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while_op(not_completed) { | ||
has_next = has_next_op(double_buffer_reader) | ||
if_else_op(has_next) { | ||
batch_data = read_op(double_buffer_reader) | ||
... (subsequent training ops) | ||
} else { | ||
reset_op(double_buffer_reader) | ||
increase_op(pass_count) | ||
not_completed = less_than_op(pass_count, reqiured_pass_num) | ||
} | ||
} | ||
``` | ||
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@@ -169,3 +173,30 @@ Two important considerations for these programs are as follows: | |
1. The multiple\_reader is the batch\_reader's underlying reader, and the batch\_reader is the double\_buffer\_reader's underlying reader. `read_op`, `has_next_op` and other reader related ops will only invoke the top-most reader. In this case, it's the double\_buffer\_reader. | ||
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2. All readers exist in both `startup_program` and `main_program`. And they are persistable. | ||
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### Simplify Configuration by MultiPassReader | ||
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The Program configuration mentioned above is somehow complicated. Users need to be very similar to concepts of Program and Block to prevent making mistakes in their code. To make the usage of C++ readers more friendly to beginning users, we introduce `MultiPassReader`. | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. The Program -> The Program (please change two spaces to one space). There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. above is somehow complicated -> above is complicated There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. beginning users -> new users There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Done. Thanks! |
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`MultiPassReader` is a decorated reader. A multi-pass reader is used to continuously yield data for several pass training. It takes the number of passes to run as one of its attributes('pass_num') and maintains a counter to record how many passes it has completed. Each time its underlying reader reaches the EOF, the multi-pass reader checks whether it has completed the training of given number of pass. If not, the underlying reader will be re-initialized and starts a new pass automatically. Before completing the whole training, the return of MultiPassReader's `HasNext()` will always be `true`. | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. several pass training -> several training passes |
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With `MultiPassReader`, the startup program would be like this: | ||
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``` | ||
multiple_reader = open_files_op(...) | ||
batch_reader = create_batch_reader_op(multiple_reader) | ||
multi_pass_reader = create_multi_pass_reader_op(batch_reader) | ||
double_buffer_reader = create_double_buffer_op(multi_pass_reader) | ||
... (other initializers) | ||
``` | ||
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The forwarding part of the corresponding `main_program` would be like this: | ||
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``` | ||
not_completed = true | ||
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. They are Fluid Variables. See my above comment. |
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while_op(not_completed) { | ||
batch_data = read_op(double_buffer_reader) | ||
... (subsequent training ops) | ||
not_completed = has_next_op(double_buffer_reader) | ||
} | ||
``` |
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Creates -> Create