Is there any method that can be used instead of crop_layer

[xua...@gmail.com]

the input data is n*c*7*7  blob，now I want to simultaneously use some crops of the inputdata w.r.t center pixel，e.x. n*c*3*3 or n*c*1*1，when I used crop_layer to obtain these cropped blobs,I found the training time became very slow, someone told me that's because the "for loop" to crop the blob image-by-image in the crop_layer function .So is there any way to improve this,or any other methods.THANKS

e.x.

layer {

  name: "crop_layer"

  type: "Crop"

  bottom: "data"

  bottom: "conv3"

  top: "crop1"

  crop_param {

    axis: 3

    offset: 3

  }

}