@hoff97/tensor-js/dist/lib/autograd/ops/util/sliceBack.js

PyTorch like deep learning inferrence library

export class SliceBack {
    constructor(a, starts, ends, axes, steps) {
        this.a = a;
        this.starts = starts;
        this.ends = ends;
        this.axes = axes;
        this.steps = steps;
        if (steps.find(x => x !== 1) !== undefined) {
            throw new Error('Slice backward pass only supports step size of 1');
        }
    }
    backward(grad) {
        if (!this.a.noGrad) {
            const shapeA = this.a.getShape();
            const rank = shapeA.length;
            const pads = new Array(rank * 2).fill(0);
            for (let i = 0; i < this.axes.length; i++) {
                pads[this.axes[i]] = this.starts[i];
                pads[rank + this.axes[i]] = shapeA[this.axes[i]] - this.ends[i];
            }
            const gradA = grad.pad(pads, 'constant', 0);
            const needed = this.a.backward(gradA);
            if (!needed) {
                gradA.delete();
            }
        }
    }
    delete() {
        if (!this.a.isLeaf()) {
            this.a.delete();
        }
    }
}
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