Modify the default for `max_new_tokens`. (#1097)

# What does this PR do?

Now clients which do not specify a max_length will be implying
`max_new_tokens = max_total_tokens - input_length`.
This is a serious change, but which seems more in line with what users
expect from standing server.

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Fixes # (issue)


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- [ ] This PR fixes a typo or improves the docs (you can dismiss the
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---------
Co-authored-by: OlivierDehaene <olivier@huggingface.co>

docs/openapi.json

@@ -367,7 +367,7 @@
             "type": "integer",
             "format": "int32",
             "example": 1,
-            "minimum": 0.0
+            "minimum": 0
           },
           "prefill": {
             "type": "array",
@@ -380,13 +380,22 @@
             "format": "int64",
             "example": 42,
             "nullable": true,
-            "minimum": 0.0
+            "minimum": 0
           },
           "tokens": {
             "type": "array",
             "items": {
               "$ref": "#/components/schemas/Token"
             }
+          },
+          "top_tokens": {
+            "type": "array",
+            "items": {
+              "type": "array",
+              "items": {
+                "$ref": "#/components/schemas/Token"
+              }
+            }
           }
         }
       },
@@ -432,7 +441,7 @@
             "type": "integer",
             "format": "int32",
             "example": 1,
-            "minimum": 0.0
+            "minimum": 0
           },
           "prefill": {
             "type": "array",
@@ -445,13 +454,22 @@
             "format": "int64",
             "example": 42,
             "nullable": true,
-            "minimum": 0.0
+            "minimum": 0
           },
           "tokens": {
             "type": "array",
             "items": {
               "$ref": "#/components/schemas/Token"
             }
+          },
+          "top_tokens": {
+            "type": "array",
+            "items": {
+              "type": "array",
+              "items": {
+                "$ref": "#/components/schemas/Token"
+              }
+            }
           }
         }
       },
@@ -486,8 +504,8 @@
             "default": "null",
             "example": 1,
             "nullable": true,
-            "minimum": 0.0,
-            "exclusiveMinimum": 0.0
+            "minimum": 0,
+            "exclusiveMinimum": 0
           },
           "decoder_input_details": {
             "type": "boolean",
@@ -505,10 +523,10 @@
           "max_new_tokens": {
             "type": "integer",
             "format": "int32",
-            "default": "20",
-            "minimum": 0.0,
-            "exclusiveMaximum": 512.0,
-            "exclusiveMinimum": 0.0
+            "default": "null",
+            "example": "20",
+            "nullable": true,
+            "minimum": 0
           },
           "repetition_penalty": {
             "type": "number",
@@ -516,7 +534,7 @@
             "default": "null",
             "example": 1.03,
             "nullable": true,
-            "exclusiveMinimum": 0.0
+            "exclusiveMinimum": 0
           },
           "return_full_text": {
             "type": "boolean",
@@ -530,8 +548,8 @@
             "default": "null",
             "example": "null",
             "nullable": true,
-            "minimum": 0.0,
-            "exclusiveMinimum": 0.0
+            "minimum": 0,
+            "exclusiveMinimum": 0
           },
           "stop": {
             "type": "array",
@@ -549,7 +567,7 @@
             "default": "null",
             "example": 0.5,
             "nullable": true,
-            "exclusiveMinimum": 0.0
+            "exclusiveMinimum": 0
           },
           "top_k": {
             "type": "integer",
@@ -557,7 +575,16 @@
             "default": "null",
             "example": 10,
             "nullable": true,
-            "exclusiveMinimum": 0.0
+            "exclusiveMinimum": 0
+          },
+          "top_n_tokens": {
+            "type": "integer",
+            "format": "int32",
+            "default": "null",
+            "example": 5,
+            "nullable": true,
+            "minimum": 0,
+            "exclusiveMinimum": 0
           },
           "top_p": {
             "type": "number",
@@ -565,15 +592,15 @@
             "default": "null",
             "example": 0.95,
             "nullable": true,
-            "maximum": 1.0,
-            "exclusiveMinimum": 0.0
+            "maximum": 1,
+            "exclusiveMinimum": 0
           },
           "truncate": {
             "type": "integer",
             "default": "null",
             "example": "null",
             "nullable": true,
-            "minimum": 0.0
+            "minimum": 0
           },
           "typical_p": {
             "type": "number",
@@ -581,8 +608,8 @@
             "default": "null",
             "example": 0.95,
             "nullable": true,
-            "maximum": 1.0,
-            "exclusiveMinimum": 0.0
+            "maximum": 1,
+            "exclusiveMinimum": 0
           },
           "watermark": {
             "type": "boolean",
@@ -653,38 +680,38 @@
             "type": "integer",
             "format": "int32",
             "example": "32000",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_best_of": {
             "type": "integer",
             "example": "2",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_concurrent_requests": {
             "type": "integer",
             "description": "Router Parameters",
             "example": "128",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_input_length": {
             "type": "integer",
             "example": "1024",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_stop_sequences": {
             "type": "integer",
             "example": "4",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_total_tokens": {
             "type": "integer",
             "example": "2048",
-            "minimum": 0.0
+            "minimum": 0
           },
           "max_waiting_tokens": {
             "type": "integer",
             "example": "20",
-            "minimum": 0.0
+            "minimum": 0
           },
           "model_device_type": {
             "type": "string",
@@ -717,7 +744,7 @@
           "validation_workers": {
             "type": "integer",
             "example": "2",
-            "minimum": 0.0
+            "minimum": 0
           },
           "version": {
             "type": "string",
@@ -743,7 +770,7 @@
             "type": "integer",
             "format": "int32",
             "example": 0,
-            "minimum": 0.0
+            "minimum": 0
           },
           "logprob": {
             "type": "number",
@@ -771,14 +798,14 @@
             "type": "integer",
             "format": "int32",
             "example": 1,
-            "minimum": 0.0
+            "minimum": 0
           },
           "seed": {
             "type": "integer",
             "format": "int64",
             "example": 42,
             "nullable": true,
-            "minimum": 0.0
+            "minimum": 0
           }
         }
       },
@@ -794,6 +821,7 @@
                 "$ref": "#/components/schemas/StreamDetails"
               }
             ],
+            "default": "null",
             "nullable": true
           },
           "generated_text": {
@@ -804,6 +832,12 @@
           },
           "token": {
             "$ref": "#/components/schemas/Token"
+          },
+          "top_tokens": {
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/Token"
+            }
           }
         }
       },
@@ -820,7 +854,7 @@
             "type": "integer",
             "format": "int32",
             "example": 0,
-            "minimum": 0.0
+            "minimum": 0
           },
           "logprob": {
             "type": "number",

router/src/lib.rs

@@ -107,8 +107,8 @@ pub(crate) struct GenerateParameters {
     #[schema(default = "false", example = true)]
     pub do_sample: bool,
     #[serde(default = "default_max_new_tokens")]
-    #[schema(exclusive_minimum = 0, exclusive_maximum = 512, default = "20")]
-    pub max_new_tokens: u32,
+    #[schema(nullable = true, default = "null", example = "20")]
+    pub max_new_tokens: Option<u32>,
     #[serde(default)]
     #[schema(nullable = true, default = "null", example = false)]
     pub return_full_text: Option<bool>,
@@ -140,8 +140,8 @@ pub(crate) struct GenerateParameters {
     pub top_n_tokens: Option<u32>,
 }
 
-fn default_max_new_tokens() -> u32 {
-    20
+fn default_max_new_tokens() -> Option<u32> {
+    None
 }
 
 fn default_parameters() -> GenerateParameters {

router/src/validation.rs

@@ -67,8 +67,8 @@ impl Validation {
         &self,
         inputs: String,
         truncate: Option<usize>,
-        max_new_tokens: u32,
-    ) -> Result<(String, usize), ValidationError> {
+        max_new_tokens: Option<u32>,
+    ) -> Result<(String, usize, u32), ValidationError> {
         // If we have a fast tokenizer
         if let Some(sender) = &self.sender {
             // Create response channel
@@ -84,6 +84,11 @@ impl Validation {
             let (inputs, input_length) = response_receiver.await.unwrap()?;
 
             // Get total tokens
+            let max_new_tokens: u32 = if let Some(max_new_tokens) = max_new_tokens {
+                max_new_tokens
+            } else {
+                self.max_total_tokens.saturating_sub(input_length) as u32
+            };
             let total_tokens = input_length + max_new_tokens as usize;
 
             // Validate MaxTotalTokens
@@ -104,7 +109,7 @@ impl Validation {
             }
 
             metrics::histogram!("tgi_request_input_length", input_length as f64);
-            Ok((inputs, input_length))
+            Ok((inputs, input_length, max_new_tokens))
         }
         // Return inputs without validation
         else {
@@ -112,6 +117,11 @@ impl Validation {
             // However, the inputs will be truncated by the python servers
             // We make sure that truncate + max_new_tokens <= self.max_total_tokens
             let input_length = truncate.unwrap_or(self.max_input_length);
+            let max_new_tokens: u32 = if let Some(max_new_tokens) = max_new_tokens {
+                max_new_tokens
+            } else {
+                self.max_total_tokens.saturating_sub(input_length) as u32
+            };
 
             // Validate MaxNewTokens
             if (input_length as u32 + max_new_tokens) > self.max_total_tokens as u32 {
@@ -121,7 +131,7 @@ impl Validation {
                 ));
             }
 
-            Ok((inputs, input_length))
+            Ok((inputs, input_length, max_new_tokens))
         }
     }
 
@@ -200,7 +210,7 @@ impl Validation {
             })
             .unwrap_or(Ok(0))?;
 
-        if max_new_tokens == 0 {
+        if max_new_tokens == Some(0) {
             return Err(ValidationError::NegativeMaxNewTokens);
         }
 
@@ -247,7 +257,7 @@ impl Validation {
             .unwrap_or(Ok(None))?;
 
         // Validate inputs
-        let (inputs, input_length) = self
+        let (inputs, input_length, max_new_tokens) = self
             .validate_input(request.inputs, truncate, max_new_tokens)
             .await?;
 
@@ -426,7 +436,7 @@ mod tests {
 
         let max_new_tokens = 10;
         match validation
-            .validate_input("Hello".to_string(), None, max_new_tokens)
+            .validate_input("Hello".to_string(), None, Some(max_new_tokens))
             .await
         {
             Err(ValidationError::MaxNewTokens(1, 10)) => (),
@@ -455,7 +465,7 @@ mod tests {
 
         let max_new_tokens = 10;
         match validation
-            .validate_input("Hello".to_string(), None, max_new_tokens)
+            .validate_input("Hello".to_string(), None, Some(max_new_tokens))
             .await
         {
             Err(ValidationError::MaxTotalTokens(6, 1, 10)) => (),
@@ -534,7 +544,6 @@ mod tests {
                 inputs: "Hello".to_string(),
                 parameters: GenerateParameters {
                     top_p: Some(0.99),
-                    max_new_tokens: 1,
                     ..default_parameters()
                 },
             })
@@ -549,7 +558,6 @@ mod tests {
                 inputs: "Hello".to_string(),
                 parameters: GenerateParameters {
                     top_p: None,
-                    max_new_tokens: 1,
                     ..default_parameters()
                 },
             })
@@ -596,7 +604,6 @@ mod tests {
                 inputs: "Hello".to_string(),
                 parameters: GenerateParameters {
                     top_n_tokens: Some(4),
-                    max_new_tokens: 1,
                     ..default_parameters()
                 },
             })
@@ -608,7 +615,6 @@ mod tests {
                 inputs: "Hello".to_string(),
                 parameters: GenerateParameters {
                     top_n_tokens: Some(0),
-                    max_new_tokens: 1,
                     ..default_parameters()
                 },
             })
@@ -620,7 +626,6 @@ mod tests {
                 inputs: "Hello".to_string(),
                 parameters: GenerateParameters {
                     top_n_tokens: None,
-                    max_new_tokens: 1,
                     ..default_parameters()
                 },
             })